FTHL ruling FWS-R8-ES-2010-0008-0042

8/7/2019 FTHL ruling FWS-R8-ES-2010-0008-0042

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Vol. 76 Tuesday,

No. 50 March 15, 2011

Part III

Department of the Interior

Fish and Wildlife Service

50 CFR Part 17Endangered and Threatened Wildlife and Plants; Withdrawal of Proposed

Rule To List the Flat-Tailed Horned Lizard as Threatened; Proposed Rule

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14210 Federal Register / Vol. 76, No. 50/ Tuesday, March 15, 2011 / Proposed Rules

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWSR8ES20100008; MO9221000008]

RIN 1018AX07

Endangered and Threatened Wildlifeand Plants; Withdrawal of ProposedRule To List the Flat-Tailed HornedLizard as Threatened

AGENCY: Fish and Wildlife Service,Interior.ACTION: Proposed rule; withdrawal.

SUMMARY: We, the U.S. Fish andWildlife Service (Service), determinethat the listing of the flat-tailed hornedlizard (Phrynosoma mcallii) as athreatened species under theEndangered Species Act of 1973, as

amended (Act), is not warranted, andwe therefore withdraw our November29, 1993, proposed rule to list it underthe Act. We made this determination inthis withdrawal because threats to thespecies as identified in the 1993proposed rule are not as significant asearlier believed, and available data donot indicate that the threats to thespecies and its habitat, as analyzedunder the five listing factors describedin section 4(a)(1) of the Act, are likelyto endanger the species in theforeseeable future throughout all or asignificant portion of its range.DATES:

The November 29, 1993 (58 FR62624), proposal to list the flat-tailedhorned lizard as a threatened species iswithdrawn as of March 15, 2011.ADDRESSES: This withdrawal of theproposed rule is available on theInternet at http://www.regulations.gov.Comments and materials received, aswell as supporting documentation forthis rulemaking is available for publicinspection, by appointment, duringnormal business hours at the U.S. Fishand Wildlife Service, Carlsbad Fish andWildlife Office, 6010 Hidden ValleyRoad, Suite 101, Carlsbad, CA 92011;telephone 7604319440; facsimile7604319624.FOR FURTHER INFORMATION CONTACT:JimBartel, Field Supervisor, Carlsbad Fishand Wildlife Office (see ADDRESSESsection). If you use atelecommunications device for the deaf(TDD), call the Federal InformationRelay Service (FIRS) at 8008778339.SUPPLEMENTARY INFORMATION:

Background

The flat-tailed horned lizard(Phrynosoma mcallii) is a small, spiny

lizard found in the Sonoran Desert ofthe southwestern United States andnorthwestern Mexico. All of the speciesof lizards in the genus Phrynosomathehorned lizardshave dorso-ventrallyflattened, pancake-likebodies; spinyscales; head spines or horns; crypticcoloration; and certain similar

behavioral traits (Sherbrooke 2003, pp.

417; Stebbins 2003, p. 299; LeacheandMcGuire 2006, p. 629).

Among horned lizard species, the flat-tailed horned lizard has particularlylong and sharp horns (Funk 1981, p.281.1; Sherbrooke 2003, p. 40; Young etal. 2004a, p. 65). Other characteristicsthat help distinguish flat-tailed hornedlizards from other members of the genusinclude a dark line down the middle ofthe back (vertebral stripe), lack ofexternal ear openings, two rows offringe scales, an unspotted vent, andas indicated by its common namealong, broad, flattened tail (Funk 1981, p.

281.1; Sherbrooke 2003, p. 40). The flat-tailed horned lizard is average in sizewhen compared to other horned lizardspecies. Flat-tailed horned lizards

become adults when about 60 to 64millimeters (mm) (2.4 to 2.5 inches (in))long, not including the tail (snout-to-vent length), and may grow to be about87 mm (3.4 in) long (Young and Young2000, p. 34; Rorabaugh and Young 2009,p. 182). The dorsal coloration of flat-tailed horned lizards varies and closelymatches the colors of the desert soils onwhich they live, ranging from pale grayto light rust-brown, while their ventralcoloration is white or cream-colored

(Funk 1981, p. 281.1; Flat-tailed HornedLizard Interagency CoordinatingCommittee [FTHLICC] 2003, p. 1;Stebbins 2003, p. 304). First described

by Hallowell in 1852, no subspecieshave been described or are recognizedfor the flat-tailed horned lizard (Crotheret al. 2008, p. 35).

The flat-tailed horned lizard occurswithin the range of the desert hornedlizard (Phrynosoma platyrhinos).Additionally, Goodes horned lizard (P.[platyrhinos] goodie), which Klauber(1935, p. 179) considered to be asubspecies of the desert horned lizard

(Klauber 1935, p. 179), also occurswithin the range of the flat-tailedhorned lizard in the portion southeast ofthe confluence of the Gila and ColoradoRivers (Mulcahy et al. 2006, p. 1823).Recent genetic analyses support Goodeshorned lizard as a differentiableevolutionary species (Mulcahy et al.2006, pp. 18071826). Hybrids betweenflat-tailed and Goodes horned lizards,exhibiting a mix of morphological andgenetic characters, have been observedsoutheast of Yuma, Arizona (Mulcahy etal. 2006, p. 1810), while apparent

hybrids between flat-tailed and deserthorned lizards have been observed inthe vicinity of Ocotillo, California(Stebbins 2003, p. 302). Additionally,the regal horned lizard (P. solare) alsooccurs in northwestern Sonora, Mexico(Rorabaugh 2008, p. 39); we are notaware of hybridization with this species.

Life HistoryFlat-tailed horned lizards are

oviparous (egg-laying), are earlymaturing, and may produce multipleclutches within a breeding season(Howard 1974, p. 111; Turner andMedica 1982, p. 819), which, when itoccurs, results in two groups ofindividuals in a single year that are allgenerally the same age (that is, twocohorts). However, some authorsquestion whether the observed twocohorts is the result of individualfemales producing two clutches in ayear or whether different groups of

females lay eggs at different times (Muthand Fisher 1992, p. 46; Young andYoung 2000, p. 11). Flat-tailed hornedlizards produce relatively small clutchesof eggs (mean clutch size = 4.7; range =3 to 7) (Howard 1974, p. 111) comparedto most other horned lizards (Sherbrook2003, p. 139). The first cohort hatchesin July to August (Muth and Fisher1992, p. 19; Young and Young 2000, p.13), and when it occurs, the secondcohort may be produced in September(Howard 1974, p. 111; Muth and Fisher1992, p. 19). Hatchlings from the firstcohort may reach sexual maturity after

their first winter season, whereasindividuals that hatch later may requirean additional growing season to mature(Howard 1974, p. 111). Flat-tailedhorned lizards typically live for 4 years,or rarely even 6 years, in the wild(FTHLICC 2003a, p. 10).

A home range is the area in which ananimal (as an individual) typically lives.Flat-tailed horned lizards can haverelatively large home ranges comparedto other species of lizards of similar size(FTHLICC 2003a, p. 9). Muth and Fisher(1992, p. 34) found the mean homerange size was 2.7 hectares (ha) (6.7

acres (ac)) on the West Mesa, California.In the Yuma Desert of Arizona, Youngand Young (2000, p. 54) found meanhome ranges for males differed betweendrought and wet years, while those offemales did not. The mean home rangesize for males was 2.5 ha (6.2 ac) duringa dry year versus 10.3 ha (25.5 ac)during a wet year. Female mean homeranges were smaller at 1.3 ha (3.2 ac)and 1.9 ha (4.7 ac) in dry and wet years,respectively (Young and Young 2000, p.54). Young and Young (2000, p. 55)noted a wide variation in movement

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14211Federal Register / Vol. 76, No. 50/ Tuesday, March 15, 2011 / Proposed Rules

patterns, with a few home rangesestimated at greater than 34.4 ha (85 ac).

Flat-tailed horned lizards are notknown to drink standing water(FTHLICC 2003a, p. 8), but theyapparently do rain-harvest (Grant 2005,pp. 6667), which is a behavior thatsome horned lizard species use tochannel precipitation or condensation

collected on the lizards body to itsmouth for consumption (Sherbrook2003, p. 104). Thus, nearly all of thewater consumed by flat-tailed hornedlizards is from the food they eat(preformed water) (FTHLICC 2003a, p.8; Grant 2005, pp. 6667). Most hornedlizard species, including the flat-tailedhorned lizard, are ant-foragingspecialists (Pianka and Parker 1975, pp.141162; Sherbrooke and Schwenk2008, pp. 447459). More than 95percent of the diet of flat-tailed hornedlizards is composed of ants, withspecies of harvester ants (genera Messor

and Pogonomyrmex) predominating inmost areas of the lizards range, butspecies ofDorymyrmex, Pheidole, andMyrmecocystus are also consumed(Pianka and Parker 1975, p. 148; Turnerand Medica 1982, p. 820; Young andYoung 2000, p. 38; FTHLICC 2003a, p.8).

Flat-tailed horned lizards, typical ofreptiles, obtain their body heat from thesurrounding environment (ectothermic)(Mayhew 1965, p. 104; Sherbrooke2003, pp. 7581). To gain body heat,they bask in the sun, often on rocks orother substrates that are warmed byinsolation. During the heat of the day,

to escape extreme surface temperatures,flat-tailed horned lizards may burythemselves just below the surface(Norris 1949, pp. 178179) or retreat toa burrow made by other organisms(Young and Young 2000, p. 12). Adultflat-tailed horned lizards are reported to

be obligatory hibernators (i.e., anorganism that must enter a dormantperiod regardless of environmentalconditions) (Mayhew 1965, p. 103).Hibernation may begin as early asOctober and end as late as March (Muthand Fisher 1992, p. 33), althoughindividuals have been noted on the

surface during January and February(FTHLICC 2003a, p. 9). Hibernationburrows appear to be self-constructed(as opposed to using burrowsconstructed by other animals) and aretypically within 10 centimeters (cm)(3.9 in) of the surface (Muth and Fisher1992, p. 33). Mayhew (1965, p. 115)found that the majority of lizardshibernated within 5 cm (2 in) of thesurface, with one as deep as 20 cm (8in) below the surface.

Flat-tailed horned lizards generally lieclose to the ground and remain

motionless when approached (Woneand Beauchamp 1995, p. 132); however,they may occasionally bury themselvesin loose sand if it is available (Norris1949, p. 176), and even more rarely, flee(Young and Young 2000, p. 12). Theirpropensity to remain motionless and

bury in the sand, along with theircryptic coloration and flattened body,

make them difficult to detect visually,which serves as a way to evadepredators but also makes them difficultfor surveyors to find in the field(FTHLICC 2003a, pp. 9, 65; Grant andDoherty 2007, p. 1050) (see alsoPopulation Dynamics section, below).

Additional life-history information isavailable in the Flat-tailed HornedLizard Rangewide Management Strategy(FTHLICC 2003a, pp. 611).

Setting and Habitat

The flat-tailed horned lizard isendemic (restricted) to the SaltonTrough and the region north of the Gulfof California in northwest Sonora,Mexico, both of which lie within theLower Colorado Subdivision of theSonoran Desert (Shreve and Wiggins1964, p. 6). The climatic conditions overthe range of the flat-tailed horned lizardare characterized by hot summertemperatures, mild winter temperatures,and little rainfall. Winter rainfallpredominates in the western portion ofthe species range while summer rainfallpredominates in the eastern portion ofthe species range (Shreve and Wiggins1964, pp. 1720, 49, 50; Johnson andSpicer 1985, p. 14). Periods of drought

are not uncommon (Shreve and Wiggins1964, p. 18).

Although the region in northwestSonora, Mexico, represents roughly halfof the current range of the flat-tailedhorned lizard, its distribution within theSalton Trough has been more dynamic.As discussed below, the geologic andland use changes in the Salton Troughhave substantially shaped the status ofthe species today.

To better understand populationtrends of the flat-tailed horned lizardrelative to the geologic setting and itscurrent distribution within sandy

habitat, we are providing a summary ofthe recent geologic history of the area inthe following paragraphs (summarizedfrom Parish 1914, pp. 85114; Sykes1914, pp. 1320; Durham and Alison1960, pp. 4791; van de Kamp 1973, pp.827848; Waters 1983, pp. 373387;Blount and Lancaster 1990, pp. 724728; Blount et al. 1990, pp. 15,46315,482; Stokes et al. 1997, pp. 6375;Patten et al. 2003, pp. 16; Li et al.2008, pp. 182197).

The Salton Trough (Trough) is a low-elevation valley that represents the

northwestward continuation of the Gulfof California. During the period startingat least several million years ago, as sealevels rose and fell, the Gulf ofCalifornia filled the present-day SaltonTrough, often extending the Gulfnorthward into the present-day SanGorgonio Pass, east of Cabazon,California. The Colorado River flowed

into the Gulf at roughly the samegeographical area as today, but with theGulf extending to a more northerlypoint, the river flowed into the Gulfmid-way along its length.

The Colorado River, which originatesin the Rocky Mountains and flowsthrough the Grand Canyon, historicallytransported large quantities of fine-grained sediment. Where the riverjoined the Gulf, sediments weredeposited forming a broad delta. Thesesediments continued to increase andcreated a barrier that divided the Gulfinto a land-locked northern portion (the

Trough) and a marine-linked southernportion (the Gulf). The northern portion,which remains below sea level butwithout a direct connection with theocean, eventually dried out. However,the Colorado River continued tomeander across its delta and seasonalflooding promoted avulsion (i.e.,abandonment of an old river channeland the creation of a new one). Thus,the river would sometimes flow into theGulf and sometimes into the Trough, thelowest point of whichreferred to asthe Salton Basinis about minus 84meters (m) elevation (277 feet (ft) belowsea level).

Water from the meandering ColoradoRiver periodically filled the SaltonBasin to varying depths (and arealextent), depositing sediments in theprocess. The lake that periodicallyformed, especially in its recent butprehistoric incarnations, is referred to

by most authors as Lake Cahuilla. Itsmaximum depth depended on elevationof the delta, which is now about 12 melevation (39 ft above sea level). TheLake was full as recently as the early1600s, but smaller, shallowermanifestations were present at varioustimes since then (including the modern

Salton Sea, discussed below). WhenLake Cahuilla was full, the ColoradoRiver water flowed into the Basin fromthe southeast, marked today by theAlamo River and New River channels,and exited the Basin farther west alonga southerly route, marked today by theRo Hardy channel, ultimately emptyinginto the Gulf of California. Floodwatersand sediments also periodically flowedinto Laguna Salada, in northwesternBaja California, Mexico. Thus, evenareas of the present-day Imperial,Mexicali, and San Luis Valleys that



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were never or were less-frequentlyinundated by Lake Cahuilla, wereregularly influenced by hydrologicforces associated with the ColoradoRiver. Despite being in the middle ofone of the driest deserts in NorthAmerica, some of these areas were, atleast periodically, part of an intricatewater distribution system of channels,

sloughs, and lagoons.Water also flowed into the Trough

from surrounding highlands, bringinglocally derived sediments with it. Onenotable inflow is marked by the present-day Whitewater River that flows into theBasin from the north. Water from thelocal sources would occasionally resultin standing water in the Basin, but thesesources could not compete with thesheer volume the Colorado Riverperiodically provided.

After flowing into the Trough for aperiod of time, the Colorado Riverwould eventually meander back andonce again flow into the Gulf. Overtime, Lake Cahuilla would then becomedry and the transported sedimentswould become exposed, with localsediment sources predominating thenorth end of the Trough, and ColoradoRiver-derived sediments predominatingthe south end of the Trough. During dryperiods, the fine-grained sediments inthe Trough would be transported andsorted by prevailing winds. Thus, muchof the Trough outside of those areas thatwere regularly influenced by theflooding and meandering of theColorado River was ultimately

blanketed with soft, friable (crumbly) or

arenaceous (sandy) soils. Similarly,sediments deposited in the ColoradoRiver delta and along the northeastshore of the Gulf of California weretransported by winds where theyformed areas of soft, friable (crumbly) orarenaceous (sandy) soils, including thesand sea of the Gran Desierto de Altar.

As a result, typical flat-tailed hornedlizard habitat today includes areas ofthese sandy flats as well as theassociated valleys created by thesegeologic events. Turner et al. (1980, p.14) stated the best habitats are generallylow-relief areas with surface soils of

packed, fine sand or low-relief areas ofpavement (hardpan) overlain with loose,fine sand. However, the availablescientific information indicates that flat-

tailed horned lizards may occur in areaswith soil substrates and plantassociations that differ from thesegeneralizations, as described below.

Flat-tailed horned lizards are alsoknown to occur at the edges of vegetatedsand dunes, on barren clay soils, andwithin sparse Atriplexspp. (saltbush)plant communities. Although Turner et

al. (1980, p. 15) suspected that theserecorded occurrences were actuallyindividuals that had dispersed frommore suitable habitats, Wone et al.(1991, p. 16) questioned this conclusion(see also Wone and Beauchamp 1995, p.132; Beauchamp et al. 1998, p. 213),suggesting instead that flat-tailedhorned lizards regularly occupy at leastsome of these areas.

Within a creosote plant community inthe West Mesa area, Muth and Fisher(1992, p. 61) found that flat-tailedhorned lizards preferred sandysubstrates with white bursage andPsorothamnus emoryi(Emory dalea),and avoided areas with creosote andTiquilia plicata (fanleaf crinklemat). InArizona, Rorabaugh et al. (1987, p.103)found flat-tailed horned lizardabundance correlated with Pleuraphisrigida (big galleta grass) and sandysubstrates, but they suggested that thepresence of sandy substrates was moreimportant than grass.

Several researchers have investigatedthe relationship between density ofperennial plants and flat-tailed hornedlizard abundance. The observedrelationships varied among studies. Forexample, Altman et al. (1980, p. ii) and

Turner and Medica (1982, p. 815) foundthe relative abundance of flat-tailedhorned lizards was significantly andpositively correlated with perennialplant density in creosote-white bursageplant communities (that is, hornedlizard abundance increased as perennialplant density increased). In contrast,Beauchamp et al. (1998, p. 210) foundflat-tailed horned lizards to be presentin higher densities in sparsely vegetatedareas with large patches of concretions(i.e., a volume of sedimentary rock inwhich a mineral cement fills the spaces

between the sediment grains), gravel,

and silt, than in areas that were sandyor densely vegetated. Altman et al.(1980, p. 7) also reported finding flat-tailed horned lizards in desert pavement

areas. Foley (2002, p. 54) found littlecorrelation in substrate texture anddistribution of flat-tailed horned lizards,when using three experimentaltreatments consisting of sandy, rockyand mixed substrates. However, Wrightand Grant (2003, p. 3) found flat-tailedhorned lizard abundance was positivelycorrelated with percentage of sandcover. Thus, flat-tailed horned lizardhabitat includes a variety of soils andother plant associations, but the habitatis best characterized as sandy flats andvalleys in a creosote-white bursage plantassociation.

Plants and harvester ants areimportant components to flat-tailedhorned lizard habitat because theycomprise its primary food chain. Seedsmake up the primary food of harvesterants (Johnson 2000, p. 92). The antsoften collect seeds from annual plants,including some nonnative species(Rissing 1988, p. 362), but they alsogather seeds from perennial plants(Gordon 1980, p. 72). Thus, a simplifiedfood chain for the flat-tailed hornedlizard may be described as follows:Plants produce seeds, harvester ants eatthe seeds, and flat-tailed horned lizardseat harvester ants.

Range and Distribution

A species range is the region overwhich it is distributed. The range of theflat-tailed horned lizard includes theSalton Trough and the region north ofthe Gulf of California. In general, this

range includes portions of southeasternCalifornia (eastern San Diego County,central Riverside County, andsouthwestern Imperial County) andsouthwestern Arizona (southwesternYuma County) in the United States, andnortheastern Baja California andnorthwestern Sonora in Mexico (Turnerand Medica 1982, p. 815) (Figure 1).Within its range, the flat-tailed hornedlizard is limited to areas below an upperelevation. Although the species has

been recorded as high as 520 m (1,706ft) above sea level (Turner et al. 1980,p. 13), flat-tailed horned lizards aremore commonly found below about 230m (about 750 ft) in elevation (FTHLICC2003a, p. 3).BILLING CODE 431055P



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Extensive manmade changes, chieflyfor agriculture, have occurred over alarge portion of the land within theSalton Trough. Below we present asummary of the history of agriculturaldevelopment in the Salton Trough(summarized from Furnish and Ladman1975, pp. 83107; Woerner 1989, pp.109112; Imperial Irrigation District

[IID] 2002, pp. 3.166 to 3.177; Pattenet al. 2003, pp. 16).

Near the start of the 20th century, acanal was built to import water to theSalton Trough from the Colorado River.The Salton Basin is below sea level andmuch of the rest of the Salton Trough isat a lower elevation than where the headof the canal was located. Thus, with theregionally abundant sunshine and river-sediment soils, the importation of water

by a gravity-fed system allowedagriculture to proliferate. For example,

by 1904 approximately 60,700 ha(150,000 ac) were in cultivation.

Unlike the current canal, the originalcanal was poorly designed because ithad no headgate to regulate flows intothe canal. Prior to extensive dams on theColorado River, the river was prone toflooding. The high waters of one suchflood during the winter of 190405flowed into the canal. Soon, nearly theentire Colorado River flowed throughthe canal, releasing water into theSalton Basin. Part of the flow followedthe two historical riverbeds (the AlamoRiver and the New River) that weredeepened and widened by the torrent.Despite heroic efforts, the flowcontinued until 1907. The Salton Basin

filled to a depth of about 22 m (72 ft)(at its deepest point) and covered about121,400 ha (300,000 ac), thus creatingthe modern Salton Sea.

Although the creation of the SaltonSea is often times described as anaccident, the inundation of the SaltonBasin by water flowing from theColorado River from 1905 to 1907 wasmerely the most recent of many suchinundations over historical andprehistorical times (see Setting andHabitat section above). Even withoutthe canal, the flood of 1905 may havenaturally flowed into the Basin.

Since the formation of the modernSalton Sea, agricultural practices in theregion have maintained the water levelsof the Salton Sea. If too much irrigationwater is allowed to evaporate in thefields, salt levels, which are high inColorado River water, build up in thesoil, making it inhospitable for crops. Toprevent this hypersalinization of thesoils, a surplus of water is used forirrigation. The excess water drains bygravity from the fields through anetwork of ditches into the Salton Sea.Even with the high evaporation rates in

the desert climate, inflow rates ofdrainage water have been high enoughto maintain, and, for a time, evenincrease, the surface water elevation ofthe Salton Sea.

Efforts to bring irrigation water to theregion continued through the 1900s, andthe system of irrigation canals waseventually improved and expanded. In

addition to the Imperial Valley, theCoachella Canal was constructed to

bring water to the southern CoachellaValley, allowing irrigated agriculture todevelop north of the Salton Sea. Similarcanal systems were built in Mexico,allowing agriculture to develop andexpand in the Mexicali and San LuisValleys. Because these systems weregravity fed, the distribution canalswithin the region were dictated byelevation, which in turn, determinedwhere irrigated agriculturaldevelopment occurred. Thus, themajority of agricultural development

was confined within the outer-most(highest elevation) canals. Moreover,croplands (and associated urbanizationand infrastructure) were contiguous inthe Salton Trough region, with little tono intervening undeveloped naturalareas. Additionally, smaller amounts ofagricultural development using pumpedgroundwater have occurred on a smallerscale outside these areas.

The geographically confinedagricultural growth in the region iscurrently limited by the amount ofwater available from the Colorado River,which is dependent on annualprecipitation in the Upper and Lower

Colorado River Basins. The amount ofirrigation water that can be delivered tothe Salton Trough from the ColoradoRiver is limited by interstate andinternational agreements (Furnish andLadman 1975, pp. 83107). Waterconservation and transfer agreementscompleted in 2003 with the San DiegoCounty Water Authority, ImperialIrrigation District, Metropolitan WaterDistrict of Southern California, andCoachella Valley Water District hasreduced the amount of water availablein the Imperial Valley and some fieldshave been fallowed, resulting in a

decrease in the amount of irrigatedagriculture in this region (IID 2006, p.1).

Aerial and satellite imagery (CarlsbadFish and Wildlife Office geographicinformation system (GIS) files)illustrates the development of activecultivation and associated urbanizationand infrastructure extending from thepresent-day delta of the Colorado River,with a longer fork extending north-northwest through the Mexicali andImperial Valleys to the Coachella Valley(punctuated by the Salton Sea), and a

smaller fork extending northeastthrough the eastern Mexicali Valley andthe San Luis Valley (Lower ColoradoRiver Valley) to Yuma. Although thereare specimens of flat-tailed hornedlizards collected historically fromwithin the now-altered region (Funk1981, p. 281.1; Johnson and Spicer1985, pp. 1424), areas of agricultural

and urban development do notconstitute habitat for the flat-tailedhorned lizard, and this continuousswath of altered land use is no longeroccupied by flat-tailed horned lizards.

The current distribution of the flat-tailed horned lizard is often describedwithin four, geographically descriptivepopulations. We use the termpopulation in this document to refer toa loosely bounded, regionallydistributed collection of individuals ofthe same species. These fourpopulations are defined as:

(1) The Coachella Valley Population,

including those individuals northwestof the Salton Sea, California;(2) The Western Population, including

those individuals in the areas west ofthe Salton Sea and the Imperial Valley,California, and west of the MexicaliValley, Baja California, Mexico;

(3) The Eastern Population, includingthose individuals in the areas east of theSalton Sea and the Imperial Valley butwest of the Colorado River; and

(4) The Southeastern Population,including those individuals in the areaseast of the Colorado River, extendingfrom Yuma south into Mexico and eastto the Gulf of California.

These current designations closelyfollow the description of populationsdiscussed in our January 3, 2003,analysis (68 FR 331), although in thatdocument we used the United States-Mexico border to further divide thepopulations (see Figure 1 above).Additionally, these populations roughlycorrespond to those used by Mulcahy etal. (2006, pp. 18071826) in theiranalysis of flat-tailed horned lizardgenetic data (see below for details). Atthe end of the Background section,

below, we summarize these fourpopulations in greater detail. We also

use these four population names toidentify the geographical habitat theyoccupy.

Populations and Genetics

The separation of the four populationsof flat-tailed horned lizards describedabove in the Range and Distributionsection is supported by genetic data, tovarying degrees. Analyses ofmitochondrial DNA data (Mulcahy et al.2006, pp. 18071826; see alsoMendelson et al. 2004, pp. 142) andnuclear microsatellite data (Culver and



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Dee 2008, pp. 114) revealed significantdifferences in the prevalence of certainalleles in flat-tailed horned lizardpopulations on either side of theColorado River; that is, the SoutheasternPopulation differs from the other threepopulations. These analyses alsoshowed that more gene flow hasoccurred near the Colorado River delta,

suggesting the shifting course of theriver over time in this area posed less ofa barrier than the more stable portionsof the river channel farther north(Mulcahy et al. 2006, p. 1822; Culverand Dee 2008, p. 11). Although Culverand Dee (2008, p. 10) noted geneticvariation in some individuals across theSoutheastern Population, they foundthat flat-tailed horned lizards in Arizonaare not genetically isolated fromneighboring populations in Mexico.Thus, the flat-tailed horned lizards eastof the Colorado River (i.e., theSoutheastern Population) may be

considered one population that issignificantly and genetically distinctfrom the populations west of the river(i.e., the Coachella Valley, Western, andEastern Populations).

The three populations west of theColorado River also showed varyinglevels of genetic differentiation.Mulcahy et al. (2006, p. 1821) noted theEastern Population was significantlydifferentiated from [the Western andCoachella Valley Populations],suggesting that there has not beensubstantial gene flow across theImperial Valley since the drying of Lake

Cahuilla.

However, the differencebetween the Coachella Valley andWestern Populations was lesspronounced. Although their differencewas supported by the presence ofhaplotypes unique to the CoachellaValley Population (Mulcahy et al. 2006,Table 1 on p. 1811, and p. 1817), thedifference between the Western andCoachella Valley Populations was notstatistically significant (the otherpopulations had unique haplotypes,too). This lack of significant differencesuggested to the authors that theCoachella Valley Population had morerecent gene flow with the WesternPopulation (Mulcahy et al. 2006, p.1821). Thus, genetic data readilysupport three of the four geographicpopulations described above, but thedistinction between the Western andCoachella Valley Populations is weak orequivocal. This suggests that theCoachella Valley Population was not a

separate population historically, but isone now because it was createdby anartificial barrier resulting from pastagricultural and urban development.

Management and Populations

Three notable managementmechanisms are in place within the U.S.portion of the flat-tailed horned lizard

range: the Interagency ConservationAgreement, which includes the Flat-tailed Horned Lizard RangewideManagement Strategy (RangewideManagement Strategy); the CoachellaValley Multiple Species HabitatConservation Plan (Coachella ValleyMSHCP); and the Lower Colorado RiverMulti-Species Conservation Plan (LowerColorado MSCP). Implementation of theInteragency Conservation Agreementhas recently positively affected and isanticipated to continue to positivelyaffect the status of flat-tailed hornedlizard populations in the United Statesand, to a lesser extent, in Mexico. Therecently permitted Coachella ValleyMSHCP is also worth noting because itis a regional habitat conservation plan(HCP) developed under section 10 of theAct that covers the flat-tailed hornedlizard in the Coachella Valley, an areaaddressed at length in our previouswithdrawals. Additionally, the LowerColorado MSCP is also an HCP thataddresses the flat-tailed horned lizard.

Interagency Conservation Agreementand Flat-tailed Horned LizardRangewide Management Strategy

In June of 1997, the Service, Bureau

of Land Management (BLM), Bureau ofReclamation (BOR), U.S. Marine Corps,U.S. Navy, Arizona Game and FishDepartment, California Department ofFish and Game (CDFG), and CaliforniaDepartment of Parks and Recreation(CDPR) entered into an InteragencyConservation Agreement. All signatoriesagreed to:

(1) Further develop and implementthe objectives, strategies, and tasks ofthe Flat-tailed Horned LizardRangewide Management Strategy[original, FTHLICC 1997, pp. 1106;revised: FTHLICC 2003a, p. 104; see

below];(2) As needed for the conservationeffort, and as available, provide programpersonnel with facilities, equipment,logistical support, and access to landsunder their control;

(3) Participate regularly in InteragencyCoordinating Committee andManagement Oversight Group meetings

to enhance communication andcooperation, and to help develop annualor other work plans and reports;

(4) Develop and distribute publicinformation and educational materialson the conservation effort;

(5) Provide ongoing review of, andfeedback on, the conservation effort;

(6) Cooperate in development of major

media releases and media projects;(7) Keep local governments,

communities, the conservationcommunity, citizens, and otherinterested and affected parties informedon the status of the conservation effort,and solicit their input on issues andactions of concern or interest to them;

(8) Whenever possible, developvoluntary opportunities and incentivesfor local communities and privatelandowners to participate in theconservation effort; and

(9) Assist in generating the fundsnecessary to implement the

conservation effort.The purpose of the Rangewide

Management Strategy is to provide aframework for conserving sufficienthabitat to maintain several viablepopulations of the flat-tailed hornedlizard throughout the range of thespecies in the United States. TheRangewide Management Strategy wasdeveloped by an interagency workinggroup over a 2-year period. Despite

being a voluntary agreement, many ofthe measures to conserve flat-tailedhorned lizards are formally incorporatedinto planning documents of

participating agencies, such as theBureau of Land ManagementsCalifornia Desert Conservation AreaPlan.

As part of the InteragencyConservation Agreement, agenciesdelineated specific areas under theirjurisdiction as Management Areas. As of2009, approximately 185,653 ha(458,759 ac) of the flat-tailed hornedlizard habitat managed by signatories ofthe Interagency Conservation Agreementexists within five Management Areas(see Table 1 below) (FTHLICC 2009, p.10). These Management Areas includethe Borrego Badlands, West Mesa, andYuha Desert (also referred to as theYuha Basin) in the Western Population,the East Mesa in the Eastern Population,and the Yuma Desert in theSoutheastern Population (Figure 2).Additionally, the Ocotillo Wells StateVehicular Recreation Area (SVRA) wasdesignated as a research area.



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The five Management Areas weredesigned to include large areas of publicland in the United States where flat-tailed horned lizards have been found,and to include most flat-tailed hornedlizard habitat identified by the FTHLICC(1997, p. 35) as key areas for survivalas determined in previous studies(Turner et al. 1980, pp. 147; Turnerand Medica 1982, pp. 815823;Rorabaugh et al. 1987, pp. 103109).Management Areas were proposed

based on standard principles of preservedesign, utilizing the best informationavailable at the time (FTHLICC 2003a, p.47).

The Management Areas weredelineated to include areas as large aspossible, while avoiding extensive,existing and predicted management

conflicts (such as off-highway vehicle(OHV) open areas). The ManagementAreas are meant to be the core areas formaintaining self-sustaining populationsof flat-tailed horned lizards in theUnited States (FTHLICC 2003a, p. 24).The Management Areas constituteroughly 42 percent of the U.S. currentdistribution. Although the majority oflands within each Management Area areState or federally owned, some private

inholdings occur within ManagementArea boundaries.

The 2003 Rangewide ManagementStrategy includes measures to avoid,minimize, and compensate impacts tothe flat-tailed horned lizard and its

habitat from construction projects andother development activities permitted

by signatory agencies. As described indetail in the Rangewide ManagementStrategy (FTHLICC 2003a, pp. 5860),the avoidance and minimizationmeasures include (in part) avoidance offlat-tailed horned lizard ManagementAreas and the Research Area, projectoversight and compliance measures,minimized project footprint, use ofexisting roads rather than creating newroads, use of barrier fencing, andproject-specific habitat restoration. TheRangewide Management Strategy

outlines avoidance, minimization, andmitigation measures intended to limitthe impacts from permitted projectswithin the Management Areas to amaximum of 1 percent of the total areaof each Management Area (FTHLICC2003a, pp. 2443). Additionally, theRangewide Management Strategy(FTHLICC 2003a, pp. 6062) describescompensation measures for projectswithin and outside the Management

Areas where residual effects wouldoccur after all reasonable on-sitemitigation has been applied. The goal ofcompensation under the RangewideManagement Strategy is to prevent thenet loss of [flat-tailed horned lizard]habitat and make the net effect of aproject neutral or positive to [flat-tailedhorned lizards] by maintaining a habitat[baseline] (FTHLICC 2003a, p. 61).Compensation funds may be used toacquire, protect, or restore [flat-tailedhorned lizard] habitat both within andcontiguous with [Management Areas](FTHLICC 2003a, p. 60). Compensationratios range from one-to-one to six-to-one (meaning, in latter ratio forinstance, that six acres-worth ofcompensation will be required for everyone acre of impact), depending on thelocation and nature of the impacts(FTHLICC 2003a, p. 61). Funds obtainedthrough compensation associated withimplementation of the RangewideManagement Strategy are being used toconsolidate land ownership within theManagement Areas or to enhance flat-tailed horned lizard habitat (FTHLICC2003a, p. 25; FTHLICC 2010, p. 8). Theoriginal and current acreages of eachManagement Area are listed in Table 1.



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TABLE 1AREA (HECTARES AND ACRES) OF FLAT-TAILED HORNED LIZARD MANAGEMENT AREAS OWNED BY SIGNATORIESTO THE INTERAGENCY CONSERVATION AGREEMENT IMPLEMENTING THE FLAT-TAILED HORNED LIZARD RANGEWIDEMANAGEMENT STRATEGY AND AREA OWNED BY NON-SIGNATORIES (PREDOMINANTLY PRIVATE) IN 1997 ANDTHROUGH 2009, PLUS AREA AND PERCENTAGE OF PROJECT-RELATED IMPACTS PERMITTED BY SIGNATORIES WITHINEACH MANAGEMENT AREA (SOURCES: FTHLICC 1997, P. 74; FTHLICC 2003A, P. 48; FTHLICC 2009, P. 10;FTHLICC 2010, P. 8)

Managementarea

Area ofsignatory landsin 1997

Area of non-signatory landsin 1997

Area of non-

signatory landsadded tosignatory lands

since 1997

Total area ofsignatory landsin 2009

Total area ofmanagementarea

Total areapermitted forimpact as of

2009

Percent of totalarea of

managementarea permittedfor impact as of2009 (percent)

Borrego Bad-lands.

14,771 ha(36,500 ac).

2,388 ha (5,900ac).

592 ha *(1,464ac).

15,363 ha(37,964 ac).

17,159 ha(42,400 ac).

0 ha (0 ac) ... ... 0.0

West Mesa ........ 46,256 ha(114,300 ac).

8,822 ha(21,800 ac).

2,624 ha (6,483ac).

48,880 ha(120,785 ac).

55,078 ha(136,100 ac).

86.77 ha(214.42 ac).

0.16

Yuha Desert ...... 23,148 ha(57,200 ac).

1,214 ha (3,000ac).

0 ha (0 ac) ...... 23,148 ha(57,200 ac).

24,362 ha(60,200 ac).

35.90 ha (88.70ac).

0.15

East Mesa ......... 43,868 ha(108,400 ac).

2,792 ha (6,900ac).

1,380 ha (3,410ac).

45,248 ha(111,810 ac).

46,660 ha(115,300 ac).

38.40 ha (94.90ac).

0.08

Yuma Desert ..... 46,741 ha(115,500 ac).

6,273 ha(15,500 ac).

6,273 ha(15,500 ac).

53,014 ha(131,000 ac).

53,014 ha(131,000 ac).

10.50 ha (25.95ac).

0.02

Total ........... 174,784 ha

(431,900 ac).

21,489 ha

(53,100 ac).

10,869 ha

(26,857 ac).

185,653 ha

(458,759 ac).

196,273 ha

(485,000 ac).

171.57 ha

(423.97 ac).

0.09

* Includes 350 ha (864 ac) owned by the Anza-Borrego Foundation.

Representatives from the agenciesparticipating on the RangewideManagement Strategy (also known asthe Interagency CoordinatingCommittee) meet several times a year tocoordinate and implement managementactions (FTHLICC 2003a, pp. 1104).The Interagency CoordinatingCommittee regularly documentsprogress made to conserve the flat-tailedhorned lizard collectively or by

participating agencies (FTHLICC 1998,pp. 111; FTHLICC 1999, pp. 113;FTHLICC 2001, pp. 124; FTHLICC2003b, pp. 132; FTHLICC 2004, pp. 133; FTHLICC 2005, pp. 137; FTHLICC2006, pp. 134; FTHLICC 2007, pp. 133; FTHLICC 2008a, pp. 135; FTHLICC2009, pp. 138; FTHLICC 2010, pp. 133). These reports document andsummarize the progress memberagencies have made towardsimplementation of the Planning Actionsidentified in Rangewide ManagementStrategy (FTHLICC 2003a, pp. 2532).The reports indicate that progress by

signatory agencies has been made in thefollowing areas: (1) Designation of thefive Management Areas and the oneResearch Area; (2) requiring actions bypermittees to follow the avoidance,minimization, and mitigation measuresoutlined in the Rangewide ManagementStrategy; (3) rehabilitating damaged anddegraded habitat within theManagement Areas; and (4) purchase oflands for flat-tailed horned lizardconservation from willing sellers.Although some lower priority actions(tasks), such as research on natural

barriers, remain outstanding, thecommittee reports that nearly all tasks,many of which are ongoing or multi-year actions, are on schedule (FTHLICC2010, pp. 2125). Thus, despite being avoluntary agreement, the signatoryagencies generally have beenimplementing the InteragencyConservation Agreement and associatedRangewide Management Strategy bymeeting regularly, working to

implement the measures of theRangewide Management Strategyincluding providing personnel,developing and distributing publicinformation, and providing ongoingreview and feedback.

Coachella Valley Multiple SpeciesHabitat Conservation Plan (CoachellaValley MSHCP)

Our past assessments of the status ofthe flat-tailed horned lizard, particularlythe 2003 withdrawal (68 FR 331),addressed the Coachella Valley indetail; thus, for consistency we again

address the Coachella Valley here andelsewhere in this document. Since the2003 withdrawal, and even since our

June 28, 2006, withdrawal (71 FR36745), we have issued an incidentaltake permit for a large, regional HCP inthe Coachella Valley. The CoachellaValley MSHCP is a large-scale, multi-jurisdictional habitat conservation planencompassing about 445,156 ha (1.1million ac) in the Coachella Valley ofcentral Riverside County. An additional27,923 ha (69,000 ac) of Tribalreservation lands distributed within the

plan area boundary are not included inthe Coachella Valley MSHCP. TheCoachella Valley MSHCP addresses 27listed and unlisted covered species,including the flat-tailed horned lizard.On October 1, 2008, the Service issueda single incidental take permit (TE1046040) under section 10(a)(1)(B) ofthe Act to 19 permittees under theCoachella Valley MSHCP for a period of75 years. Participants in the Coachella

Valley MSHCP include eight cities(Cathedral City, Coachella, IndianWells, Indio, La Quinta, Palm Desert,Palm Springs, and Rancho Mirage); theCounty of Riverside, including theRiverside County Flood Control andWater Conservation District, RiversideCounty Parks and Open Space District,and Riverside County WasteManagement District; the CoachellaValley Association of Governments;Coachella Valley Water District;Imperial Irrigation District; CaliforniaDepartment of Transportation;California State Parks; Coachella ValleyMountains Conservancy; and theCoachella Valley ConservationCommission (the created joint powersregional authority). The CoachellaValley MSHCP was designed toestablish a multiple species habitatconservation program that minimizesand mitigates the expected loss ofhabitat and incidental take of coveredspecies, including flat-tailed hornedlizard (USFWS 2008, pp. 1207, andAppendix A, pp. 298328). TheCoachella Valley MSHCP is also aSubregional Plan under the State of



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Californias Natural CommunityConservation Planning (NCCP) Act, asamended.

The permit covers incidental takeresulting from habitat loss anddisturbance associated with urbandevelopment and other proposedcovered activities. These activitiesinclude public and private development

within the plan area that requirediscretionary and ministerial actions bypermittees subject to consistency withthe Coachella Valley MSHCP policies.An associated Management andMonitoring Program is also included inthe Coachella Valley MSHCP andidentifies specific management actionsfor the conservation of the flat-tailedhorned lizard and its habitat.

The Coachella Valley MSHCPidentifies a reserve system that, uponfull implementation, will establish 21conservation areas that are eitheradjacent to each other or are linked by

biological corridors. The acquisitionprogram for the plans reserve system isdesigned to conserve 52,484 ha (129,690ac) during the first 30 years. Thisprogram is to be implemented such thatacquisitions occur commensurate (inrough step) with impacts from urbandevelopment that is covered under theplan.

The flat-tailed horned lizard is nowknown to occur only at two locations

within the Coachella Valley MSHCParea, the Thousand Palms and DosPalmas conservation areas (CVCC 2010,p. 13) (see also Description of SpecificPopulations section below). Table 2describes the amount of flat-tailedhorned lizard habitat conserved andidentified to be conserved throughimplementation of the Coachella ValleyMSHCP. Additionally, planimplementation is expected to limitimpacts of development and othercovered activities on lands withinconservation areas but that have not yet

been acquired for conservation as part ofthe Coachella Valley MSHCP reservesystem. The plan also designates onecore habitat area (as used in that plan,this refers to an area that is large enoughto maintain a self-sustainingpopulation)the Thousand Palmsconservation areaand commits toestablishing two more self-sustainingpopulations in other parts of the reservesystem, if feasible, to benefit the flat-tailed horned lizard. Because of thedistances separating appropriate parts ofthe reserve system, relocation of flat-tailed horned lizards will be required tore-establish or enhance populations insuitable habitat areas that have thepotential to, but currently do not,support self-sustaining populations.Additionally, the plan calls for

Management and Monitoring Programsthat are expected to conserve thisspecies in the plan area. Requiredmanagement activities include limitingactivities that degrade flat-tailed hornedlizard habitat, evaluation andmanagement of edge effects and otherimpacts through adaptive management,control of invasive species wherenecessary, and restoration andenhancement of degraded habitat asnecessary according to monitoringresults (CVAG 2007, p. 9123). In ourevaluation of the potential impacts ofthe plans implementation on the flat-tailed horned lizard (USFWS 2008, p.178), we concluded: After reviewingthe current status of this species,environmental baseline for the actionarea, effects of the proposed action, andcumulative effects, it is the Services

biological opinion that the action, asproposed, is not likely to jeopardize the

continued existence of the flat-tailedhorned lizard. Loss of the CoachellaValley population would have anegligible [effect] on the status of thespecies as a whole, since it makes upapproximately 1 percent of the currentrange of the flat-tailed horned lizard.Persistence of the species in the Planarea is likely only with effective Planimplementation.

TABLE 2AREA OF FLAT-TAILED HORNED LIZARD HABITAT CONSERVED, ANTICIPATED TO BE CONSERVED, IMPACTED,AND ANTICIPATED TO BE IMPACTED THROUGH IMPLEMENTATION OF THE COACHELLA VALLEY MSHCP

Criterion (source) Thousand Palms Dos Palmas

Flat-tailed horned lizard habitat area conserved at permit issuance in2008 (CVAG 2007, p. 9115).

1,318 ha (3,256 ac) 608 ha (1,503 ac)

Additional flat-tailed horned lizard habitat area conserved in 2008(CVCC 2009, p. 79).

274 ha (678 ac) 107 ha (265 ac)

Additional flat-tailed horned lizard habitat area conserved in 2009(CVCC 2010, pp. 39 & 51).

8 ha (20 ac) 0 ha (0 ac)

Total flat-tailed horned lizard habitat area under conservation through2009 (calculated).

1,600 ha (3,954 ac) 715 ha (1,768 ac)

Total flat-tailed horned lizard habitat area expected to be conserved byMSHCP implementation (CVAG 2007, p. 9115).

1,707 ha (4,219 ac) 2,078 ha (5,134 ac)

Percent flat-tailed horned lizard habitat area conserved through 2009compared to amount required upon full implementation of the plan(calculated).

94% 34%

Area of flat-tailed horned lizard habitat impacted by permitted activitiesthrough 2009 (CVCC 2009, p. 79; CVCC 2010, pp. 39 & 51).

0 ha (0 ac) 0 ha (0 ac)

Area of flat-tailed horned lizard habitat anticipated to be impacted by

permitted activities (CVAG 2007, p. 9115).

44 ha (108 ac) 163 ha (403 ac)

Percent flat-tailed horned lizard habitat area anticipated to be impactedcompared to total area of flat-tailed horned lizard habitat in conserva-tion area (calculated).

2% 7%

Lower Colorado River Multi-SpeciesConservation Plan (Lower ColoradoRiver MSCP)

The Lower Colorado River MSCP is ajoint effort by Federal and non-Federal(State, local, and private) entities withmanagement authority for storage,

delivery, and diversion of water;hydropower generation, marketing, anddelivery; and land management orNative American Trust responsibilitiesalong the Lower Colorado River, toaddress regulatory requirements undersections 7, 9, and 10 of the Act for their

activities. We issued the 50-year permit(TE086834) on April 4, 2005. Most ofthe activities addressed by the LowerColorado MSCP are outside the range ofthe flat-tailed horned lizard. The flat-tailed horned lizard habitat containedwithin the Lower Colorado River MSCP



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planning area is under control ofagencies, especially the Bureau ofReclamation, that have agreed toimplement the Rangewide ManagementStrategy (USFWS 2005, p. 202).

Implementation of the LowerColorado River MSCP is expected toprovide for the acquisition and long-term protection of 230 acres of existing

flat-tailed horned lizard habitat that iscurrently unprotected. This action iscompensation for anticipated impacts toapproximately 128 acres of flat-tailedhorned lizard habitat (USFWS 2005, pp.201202). Purchase of protected habitat,potentially near the Dos Palmas reservearea, is scheduled to start in 2011 (BOR2010, p. 274). Additionally, activitiescovered under the permit will bedesigned to avoid or minimize effects tothe species and its habitat in accordancethe conservation needs identified in theRangewide Management Strategy(USFWS 2005, pp. 201202).

We found that implementation of theLower Colorado River MSCP was NotLikely to Jeopardize the ContinuedExistence of the Species (USFWS 2005,p. 202), noting The habitat area thatwould be included [under the plan] isnot a significant amount of the availablehabitat for the species. * * * Researchand monitoring of the species within the[Lower Colorado River MSCP] area willcontribute to understanding the species,its distribution, and habitat needs.* * * [and] There are not likely to beany adverse effects to the speciesconservation elsewhere in the rangefrom the issuance of an incidental take

permit for the [Lower Colorado RiverMSCP] (USFWS 2005, p. 202).

Population Dynamics

Flat-tailed horned lizards are difficultto detect, which limits the effectivenessof surveys for the species (FTHLICC2003a, pp. 9, 65; Grant and Doherty2007, p. 1050). As a result, not only ispresence and especially absencedifficult to determine, but determiningthe size, trend, and demography ofpopulations is problematic as well. Thehistory of flat-tailed horned lizardmonitoring and the shortcomings of the

techniques used are described in theRangewide Management Strategy(FTHLICC 2003a, p. 64) and our 2003withdrawal document (68 FR 332333).Monitoring using more rigorous datacollection and analytical methodologieshas been conducted as part of theimplementation of the RangewideManagement Strategy (FTHLICC 2003a,pp. 6466; FTHLICC 2008b, pp. 138).The results from this monitoring effortare described below.

As detailed in the Flat-tailed HornedLizard Monitoring Plan (FTHLICC

2008b, pp. 138), flat-tailed hornedlizard monitoring consists of twosurveys used in tandem: (1) Occupancyestimation surveys and (2) demographicplot surveys. Occupancy estimation wasdesigned to determine whether thedistribution (but not numbers ofindividuals or densities) of flat-tailedhorned lizards in the management and

research areas is stable, increasing, ordecreasing. This component of themonitoring was meant to detect large-scale changes in the status of flat-tailedhorned lizard distribution in theManagement Areas. The monitoring ofdemographic plots was designed todelineate flat-tailed horned lizardpopulation dynamics and trends byestimating abundance each summer andyearly survival, recruitment, andpopulation growth rate between years.This component was meant to gathermore in-depth information on a smallernumber of plots. However, the

demographic plots were non-randomlyestablished within areas known orsuspected to support greater densities offlat-tailed horned lizards. TheManagement Areas overall wereselected because they providedgenerally high-quality flat-tailed hornedlizard habitat. However, the use of thetwo complementary survey types, onedispersed and coarse and the otherfocused and narrow, allows managers todraw, with caution, more detailedconclusions about an entireManagement Area than they could haveotherwise done by interpreting just one

of the survey types alone. Below wesummarize the information availablefrom these monitoring efforts (source:USFWS 2010a, pp. 176).

Occupancy surveys were conducted atWest Mesa (2005 and 2009), East Mesa(2006), Yuha Desert (2008), and OcotilloWells State Vehicular Recreation Area(SVRA) (20062009). Separateoccupancy analyses of these areas wereconducted based on three surveymethodologies: visual observations offlat-tailed horned lizards, lizard scatobservations, and a combination ofvisual and scat observations. Multi-yearanalyses also were conducted for asubset of 53 plots in Ocotillo WellsSVRA that were surveyed annually from2006 to 2009. Our analysis indicates thecombined visual-and-scat surveys werethe most likely to correctly yield astatistically significant result (i.e., thissurvey methodology had the greateststatistical power). Although there are nocomparable historical data with whichto provide context, our analysis suggeststhat the level of occupancy of flat-tailedhorned lizards within the surveyedareas seemed relatively high at all sites.

For example, visual-and-scat surveyresults show that flat-tailed hornedlizards occupied at least 80 percent ofthe Management Areas in the yearssurveyed, except in the West MesaManagement Area in 2005, which had alow level of survey effort that year.Additionally, results from the 53-plotsubset with multi-year data from 2006 to

2009 suggested that the level of flat-tailed horned lizard occupancy stayedabout the same or may have evenincreased slightly over time. Moreover,our analysis showed considerablesupport to conclude that there was nolinear decline in the proportion ofsurvey plots occupied by flat-tailedhorned lizards. These results onlyreflect the occupancy of flat-tailedhorned lizards within the areassurveyed and do not necessarily reflectthe level of occupancy throughout therange of the species; nevertheless, weconclude from the above results that the

level of occupancy within the surveyareas is not low, and that there is noindication of a decline.

Data from the demographic plots weregathered from six 9-hectare (22.2-acre)plots at the following flat-tailed hornedlizard Management Areas: East Mesa (1plot, 20072009), West Mesa (1 plot,20072009; 1 plot, 20082009), YuhaDesert (1 plot, 20072009), and YumaDesert (2 plots, 20082009). Hatchlingswere captured at all Management Areasexcept East Mesa (which was surveyedprior to the time that flat-tailed hornedlizards eggs would have been likely tohave hatched), indicating that flat-tailed

horned lizards were reproducing. Thepresence of hatchlings during 2008, andespecially 2009, suggested thatreproductive conditions were favorablein those years.

Because of the complexities ofanalyzing a cryptic species, we used twomethodologies to calculate flat-tailedhorned lizard abundance. Because thesurveyed plots were not closed(meaning flat-tailed horned lizardscould move in and out of the areas beingsurveyed), we used two differentmethods (calculations) to estimate theeffective survey area so that we could

translate abundance (number ofindividuals) into densities (number ofindividuals per unit area). Using thefirst method (using a mean maximumdistance moved buffer strip to estimateeffective survey area), the density ofadult flat-tailed horned lizards rangedfrom 0.3 to 3.3 individuals per ha (0.1to 1.3 individuals per ac), while thesecond method (using a hierarchical,spatially indexed capture-recapturemodel to estimate effective survey area)yielded a range from 0.7 to 4.4individuals per ha (0.3 to 1.8



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individuals per ac). The results from thesecond method are likely to be morerealistic because they incorporatedadditional spatial information.

Other estimates of density of flat-tailed horned lizards are available in thescientific literature, but comparisons

between and among the different studies(including the recent monitoring) are

confounded by differing survey andanalysis methodologies. Nevertheless,the above densities at the threeCalifornia Management Areas weregenerally within the range of estimatesreported by Grant (2005, pp. 3940)during 20022004. Similarly, thedensities of adult flat-tailed hornedlizards at the Yuma Desert ManagementArea reported above were generallysimilar to the ranges of estimatespresented by Young and Young (2000,p. 28) during 19971998, Young et al.(2004b, p. i) during 2003, and Youngand Royle (2006, p. 9) in 2005.

Comparisons to even earlier estimationsof flat-tailed horned lizard densities,although even more tenuous because ofdiffering methodologies, are also withinsimilar ranges. Despite similar ranges indensities reported from the variousstudies through time, the increasedstatistical and methodological rigor ofrecent efforts has reduced the level ofuncertainty in the results. Thus, theserecent density estimates are animprovement over older estimates.

The available data indicate that flat-tailed horned lizard abundances anddensities have remained relativelystable from 2007 to 2009; however, with

only 3 years of standardized monitoring,these data cannot yet providemeaningful inferences about long-termtrends. Additionally, no abundance ordensity information is available for thelower-quality habitat areas outside thedemographic plots. However, thecomplementary coarse-scale occupancysurvey data mentioned above suggestsflat-tailed horned lizards are widelydistributed spatially and, in at least atone Management Area, temporallyconsistent. This conclusion suggeststhat flat-tailed horned lizard populationtrends in the surveyed lower-quality

habitat areas are not dissimilar to thoseof the surveyed higher-quality habitatareas. Moreover, because the recent(20072009) and older (19972005)density estimates are all generallywithin similar ranges, this suggests theoverall density of flat-tailed hornedlizards within the surveyedManagement Areas has not markedlydecreased over the past decade or so.Thus, with the previously mentionedcaveats in mind, we conclude that flat-tailed horned lizard populations in theManagement Areas are not low and have

not declined since 2007, and probablynot declined since 1997.

Description of Specific Populations

As stated earlier, we have divided thecurrent range of the flat-tailed hornedlizard into four populations based ongeographic locales. The 2003 RangewideManagement Strategy includes a GIS-

based map (FTHLICC 2003a, p. 5) of thecurrent distribution of the flat-tailedhorned lizard. Except for the CoachellaValley Population, where the flat-tailedhorned lizard is now limited to twooccurrences, we used the GIS data as a

basis for our assessment of thedistribution of flat-tailed horned lizardpopulations. A summary of thesepopulations is presented below.

Coachella Valley Population(California)The current distributionwithin the Coachella Valley as defined

by the Rangewide Management Strategy(FTHLICC 2003a, pp. 35) does notrepresent the best scientific distributioninformation available for this region.Urban and agricultural development hascontinued in the Coachella Valley, andthere are many areas of unsuitable ordegraded habitat. In addition to areas ofunsuitable habitat, many of which serveas a barrier to flat-tailed horned lizardmovement, other potential manmade

barriers exist, including several majorhighways, a railway, and canals. Theonly area within the Coachella Valleyproper that is now known to beoccupied by flat-tailed horned lizards isin the Thousand Palms reserve (CVCC2010, p. 13). Other areas of potentially

suitable habitat occur in the region,including areas that were formerlyknown to be occupied (Barrows et al.2008, p. 1891), although recent surveyshave not detected any flat-tailed hornedlizards (CVCC 2010, p. 13). Thus, thecurrent distribution as defined by theRangewide Management Strategy(FTHLICC 2003a, pp. 35) does notaccurately reflect the area occupied byflat-tailed horned lizards in theCoachella Valley; as such, we do not usea GIS-based assessment for theCoachella Valley as we do for the othergeographical populations.

The Coachella Valley MSHCP is theprimary driver of monitoring andmanagement activities for the CoachellaValley Population of the flat-tailedhorned lizard because the RangewideManagement Strategy does not includeany Management Areas in this region.The Coachella Valley Population area isthe smallest of the four geographicpopulations, and we primarilyidentify it as a separate population to beconsistent with our past analyses. Flat-tailed horned lizards also occur in thevicinity of the Dos Palmas Preserve near

the northeast shore of the Salton Sea(Turner and Medica 1982, p. 817;FTHLICC 2003a, pp. 26; CVCC 2010, p.13). The Dos Palmas population is smalland likely isolated from otherpopulations because of the presence ofthe Salton Sea to the west; canals, roadsand urban and agricultural developmentto the northwest; and canals, roads and

urban and agricultural development tothe southeast. However, not all of these

barriers are likely to completely restrictflat-tailed horned lizard movement (seethe Factor E discussion, below). Thegenetic affinities of the Dos Palmaspopulation are not known.Geographically, the flat-tailed hornedlizards at Dos Palmas Preserve couldarguably be considered part of either theWestern Population or EasternPopulation (see below); however,

because the true affinities of thispopulation are not known, and becausethe Dos Palmas reserve area is covered

under the Coachella Valley MSHCP andits associated monitoring andmanagement, herein we consider theDos Palmas flat-tailed horned lizards to

be part of the Coachella ValleyPopulation. The area of flat-tailedhorned lizard habitat in the CoachellaValley Population is about 3,785 ha(9,353 ac) (see Table 2).

Western Population (California andBaja California)This populationincludes flat-tailed horned lizards in theareas west of the Salton Sea, theImperial Valley, and the MexicaliValley. Using a GIS-based assessment to

estimate the area of this portion of thecurrent distribution as defined by theRangewide Management Strategy(FTHLICC 2003a, pp. 35), we estimatedthat the Western Population occupies341,989 ha (845,073 ac). Of this acreage,approximately 253,020 ha (625,226 ac)is within the United States. Within theU.S. portion of the Western Population,approximately 48,262 ha (119,258 ac),or about 19 percent, is non-Federal ornon-State owned, or is more likely to bedeveloped. The habitat within this areais mostly intact except for a fewdeveloped areas, but as discussed in theBarriers and Small Populationssection under Factor E, potentialmanmade barriers to flat-tailed hornedlizard movement (in addition to areas ofurban and agricultural development)include Interstate 8; State Routes 78, 86,and 98; two railways; the fence andother activities along the international

border in the United States, and MexicoFederal Highway 2 in Mexico. TheRangewide Management Strategydesignates three Management Areas inthis population area, including BorregoBadlands, West Mesa, and Yuha Desert



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(see Table 1), and a research area at theOcotillo Wells SVRA. Much of thewesternmost portion of this populationis within Anza-Borrego Desert StatePark. Additionally, private lands arescattered throughout the U.S. portion,with large aggregations in the BorregoSprings area and in the vicinity of (butoutside of) Ocotillo Wells SVRA. The

range of the flat-tailed horned lizard inthis population also extends southwardinto Mexico, crossing the international

border at the Yuha Desert andcontinuing south along the east side ofthe Peninsular Ranges and west ofLaguna Salada in Baja California(FTHLICC 2003a, pp. 25). The status ofthe population in this portion of therange in Mexico is poorly known, butthere have been few substantive changesto the landscape in this area.Additionally, flat-tailed horned lizardswere observed recently near CerroPrieto, Baja California, which is east of

the Sierra de Los Cucapahs (SierraCucapa) and west of the agriculturalareas of the Mexicali Valley (A. CalvoFonseca, Pronatura Noroeste, in litt.2010). This recent detection is outsideof the current distribution as depicted inthe Rangewide Management Strategy(FTHLICC 2003a, p. 5).

Eastern Population (California andBaja California)This populationincludes flat-tailed horned lizards in theareas east of the Salton Sea and theImperial Valley but west of the ColoradoRiver. While the isolated population atDos Palmas Preserve could be included

as part of either the Eastern Populationor the Coachella Valley Populationbased on its geographic location, for thepurposes of our analysis of threats to thespecies we consider the Dos PalmasPreserve population to be part of theCoachella Valley Population because ofthe similarity of potential threats whencompared to the populations in theCoachella Valley, and its inclusionwithin the Coachella Valley MSHCPplan area. Using a GIS-based assessmentto estimate the area of the EasternPopulation portion of the currentdistribution (as defined by the

Rangewide Management Strategy(FTHLICC 2003a, pp. 35)), weestimated that the Eastern Populationoccupies 169,617 ha (419,133 ac). Ofthis acreage, approximately 146,121 ha(361,073 ac) is within the United States.Within the U.S. portion of the EasternPopulation, approximately 5,844 ha(14,441 ac), or about 4 percent, is non-Federal or non-State owned, or is morelikely to be developed. The areaoccupied by the Eastern Population ismostly intact except for a few developedareas, but potential manmade barriers to

flat-tailed horned lizard movement (inaddition to areas of urban andagricultural development) includeInterstate 8, State Routes 78 and 98, theAll-American Canal and the CoachellaCanal, and the international borderfence in the United States (see Barriersand Small Populations section underFactor E, below). The Rangewide

Management Strategy designated theEast Mesa Management Area within thearea occupied by the Eastern Population(see Table 1). The geographic extent ofthe Eastern Population also includes theAlgodones Dunes (also known as theImperial Sand Dunes or Glamis SandDunes), a portion of which is designatedWilderness, and a narrow strip ofhabitat south of the international borderat the southern edge of the AlgodonesDunes (FTHLICC 2003a, pp. 25). Theportion of the Eastern Population area inMexico is bound by agriculturaldevelopment (unsuitable habitat) on the

west, south, and east. The status of theportion of the Eastern Population inMexico is poorly known, but flat-tailedhorned lizards were observed recentlyin this area (A. Calvo Fonseca, in litt.2010).

Southeastern Population (Arizona andSonora)This population includes flat-tailed horned lizards in the areas east ofthe Colorado River, extending fromYuma, Arizona, south and east to theGulf of California in northwesternMexico. In Arizona, the flat-tailedhorned lizard occurs in Yuma County,ranging over the Yuma Desert south ofthe Gila River and west of the Gila and

Butler Mountains (Rorabaugh et al.1987, p. 104; FTHLICC 2003a, pp. 26).The Rangewide Management Strategydesignated the Yuma DesertManagement Area within the areaoccupied by the SoutheasternPopulation (see Table 1). In Mexico, theflat-tailed horned lizard ranges from theinternational border in the Yuma Desertsouth and east through the PinacateRegion to the sandy plains aroundPuerto Pen asco and Bahia de San Jorgealong the Gulf of California (Johnsonand Spicer 1985, p. 13; Gonzales-Romero and Alvarez-Cardenas 1989, p.

519; FTHLICC 2003a, pp. 25). About 60percent of the flat-tailed horned lizardhabitat in Sonora lies within twoMexican Federal natural protectedareas: the Upper Gulf of California andColorado Delta Biosphere Reserve, andthe Pinacate and Gran Desierto de AltarBiosphere Reserve (CEDO 2001, p. 3).

Using a GIS-based assessment toestimate the area of this portion of thecurrent distribution as defined by theRangewide Management Strategy(FTHLICC 2003a, pp. 35), we estimatedthat the area occupied by the

Southeastern Population is 1,073,551 ha(2,652,802 ac), by far the largest of thefour population areas. Of this acreage,approximately 67,922 ha (167,839 ac) iswithin the United States. Within theU.S. portion of the SoutheasternPopulation, approximately 5,158 ha(12,746 ac), or about 8 percent, isprivately owned; an additional 5,832 ha

(14,411 ac), or about 9 percent, is Stateof Arizona-owned lands. The habitatwithin the Southeastern Population areais mostly intact except for a fewdeveloped areas, but potential barriersto flat-tailed horned lizard movement(in addition to areas of urban andagricultural development) includeInterstate 8 and the Yuma Areas ServiceHighway in the United States; theinternational border (combined withMexico Federal Highway 2); MexicoFederal Highway 8; and a railway inMexico (see Barriers and SmallPopulations section under Factor E,

below).In summary, using a GIS-basedassessment to estimate the size of thecurrent distribution of the flat-tailedhorned lizard as defined by theRangewide Management Strategy(FTHLICC 2003a, p. 5), we estimatedthat the three population areas(excluding the Coachella ValleyPopulation) comprise roughly 1,585,000ha (3,916,600 ac), of whichapproximately 467,000 ha (1,154,000 ac)(less than 30 percent) is within theUnited States and approximately1,100,000 ha (2,718,000 ac) (more than70 percent) is within Mexico. The area

of flat-tailed horned lizard habitatoccupied or likely to be occupied thatalready is or is expected to be conservedin the Coachella Valley Population isabout 3,785 ha (9,353 ac) (see Table 2).

Previous Federal Actions

In 1982, we first identified the flat-tailed horned lizard as a category 2candidate species for listing under theAct (47 FR 58454; December 30, 1982).Category 2 candidate species were taxafor which information now inpossession of the Service indicates thatproposing to list the species as

Endangered or Threatened is possiblyappropriate, but for which sufficientdata on are not currently available to

biologically support a proposed rule(47 FR 58454). We again identified theflat-tailed horned lizard as a category 2candidate species in our 1985 notice ofreview (50 FR 37958; September 18,1985). In 1989, we elevated the speciesto category 1 status (54 FR 554; January6, 1989). Category 1 included speciesfor which the Service currently hassubstantial information on hand tosupport the biological appropriateness



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of proposing to list as endangered orthreatened (54 FR 554). We maintainedthe category 1 status for the flat-tailedhorned lizard in our 1991 notice ofreview (56 FR 58804; November 21,1991).

On November 29, 1993, we publishedin the Federal Register a proposed ruleto list the flat-tailed horned lizard as a

threatened species under the Act (58 FR62624). On February 22, 1994 (59 FR8450), we published a notice reopeningthe public comment period andannouncing that we had scheduled apublic hearing on March 22, 1994, inImperial, California, in response to arequest from the public. Our November15, 1994, candidate notice of reviewstated that we had proposed to list thespecies as threatened (59 FR 58982).

Subsequently, the passage of PublicLaw 1046, 109 Stat. 73 on April 10,1995, resulted in a delay in our finallisting determination for the flat-tailedhorned lizard. Although the statutesprimary purpose was to provideadditional funds for overseas militaryoperations, it also included a rider thatwithdrew funding for listingdeterminations. Through a series ofmoratoria, funding restrictions, andcontinuing resolutions, this restrictionin use of funds remained in effect untilApril 26, 1996, when the OmnibusAppropriations Act was enacted (Pub. L.104134, 110 Stat. 1321, (1996)), whichcontained a moratorium on certainlisting activities but allowed thePresident to waive the moratorium. OnApril 26, 1996, President Clinton

suspended the provision limitingimplementation of Section 4 of the Act(61 FR 24667; May 16, 1996). Earlier in1996, our notice of review had indicatedthat we had proposed to list the speciesas threatened (61 FR 7596; February 28,1996).

On January 21, 1997, the Bureau ofLand Management (BLM) announced inthe Federal Register that the draft Flat-tailed Horned Lizard RangewideManagement Strategy was available forpublic comment (62 FR 3052). On May16, 1997, in response to a lawsuit filed

by the Defenders of Wildlife and other

plaintiffs to compel us to make a finallisting determination on the flat-tailedhorned lizard, the District Court inArizona ordered us to issue a finallisting decision within 60 days. In June1997, several State and Federalagencies, including the Service, signedan Interagency Conservation Agreementcommitting to implement the recentlyfinalized Flat-tailed Horned LizardRangewide Management Strategy(FTHLICC 1997, pp. 1106). Pursuant tothe Interagency ConservationAgreement, cooperating parties agreed

to take voluntary steps aimed atreducing threats to the species,stabilizing the species populations, andmaintaining its ecosystem (seeFTHLICC 2003a, p. 80).

On July 15, 1997, we issued a finaldecision to withdraw the proposed ruleto list the flat-tailed horned lizard as athreatened species (62 FR 37852). We

based the withdrawal on three factors:(1) Population trend data did notconclusively demonstrate significantpopulation declines; (2) Some of thethreats to the flat-tailed horned lizardhabitat had abated since the proposedrule was issued; and (3) Our conclusionthat the recently approved InteragencyConservation Agreement would ensurefurther reductions in threats (62 FR37852).

On December 30, 1997, the Defendersof Wildlife and others filed a complaintin the U.S. District Court for theSouthern District of Californiachallenging our 1997 withdrawal of theproposed rule. On June 16, 1999, theDistrict Court upheld our decision towithdraw the proposed listing rule. TheDistrict Courts decision was appealedand on July 31, 2001, the Ninth CircuitCourt of Appeals vacated the previousruling of the District Court. The casewas remanded back to the Secretary

because: (1) The withdrawal of theproposed rule did not expresslyconsider whether the flat-tailed hornedlizard is likely to become an endangeredspecies within the foreseeable future ina significant portion of its range; and (2)The withdrawal of the proposed rule

did not address the lizards viability ina site-specific manner with regard to theputative benefits of the InteragencyConservation Agreement. Inaccordance with the Appeals Courtsruling, we published a document in theFederal Register on December 26, 2001,reinstating the 1993 proposed rule andopening a 120-day public commentperiod (66 FR 66384).

On May 30, 2002, we published adocument in the Federal Registerreopening the public comment periodfor an additional 60 days (67 FR 37752)and announced that we would be

holding public hearings in El Centro,California, on June 19, 2002. OnSeptember 24, 2002, we published inthe Federal Register another document(67 FR 59809) announcing thereopening of the public comment periodfor an additional 15 days to allow forpeer review, additional public commenton the proposed rule, and submittal ofinformation that became available sinceour 1997 withdrawal.

On January 3, 2003, we againpublished in the Federal Register adecision to withdraw the November 29,

1993, proposed rule to list the flat-tailedhorned lizard as a threatened species(68 FR 331). The Service found thelizard to be in danger of extirpation inthe Coachella Valley (68 FR 348);however, we determined that theCoachella Valley is not a significantportion of the species range. Weconcluded in the January 3, 2003,

withdrawal that the flat-tailed hornedlizard populations on either side of theImperial Valley-Salton Sea and inArizona were not likely to becomeendangered in the foreseeable futureand that listing the species was notwarranted.

The Tucson Herpetological Societyand others filed a complaint with theDistrict Court for the District of Arizonachallenging the January 3, 2003,withdrawal of the proposed rule. In aruling issued on August 30, 2005, theDistrict Court for the District of Arizonaissued an order granting plaintiffs

motion for summary judgment, citingour failure to specifically evaluate thelost habitat of the flat-tailed hornedlizard, and whether the amount of losthabitat represented a significant portionof the species range. On December 7,2005, we published a document in theFederal Register reinstating the 1993proposed rule (70 FR 72776). On March2, 2006, we announced in the FederalRegister that we were reopening thepublic comment period on the 1993proposed rule for 14 days for thepurpose of soliciting comments andinformation relevant to the specificissue identified in the District Courts

November 2005 ruling (i.e., whether theflat-tailed horned lizards lost historicalhabitat rendered the species likely to

become in danger of extinction in theforeseeable future throughout all or asignificant portion of its range) (71 FR10631). On April 21, 2006, weannounced in the Federal Register anadditional public comment period onthe 1993 proposed rule from April 21,2006, to May 8, 2006 (71 FR 20637).

After re-examining the lost historicalhabitat of the flat-tailed horned lizard inrelation to our January 3, 2003,withdrawal, we determined that the lost

historical habitat is not a significantportion of the species range, and its lossdoes not result in the species likely

becoming endangered in the foreseeablefuture throughout all or a significantportion of its range. We published ourdecision in the Federal Register on June28, 2006, to once again withdraw theNovember 29, 1993, proposed rule tolist the flat-tailed horned lizard as athreatened species (71 FR 36745).

Following a supplemental complaintfrom Tucson Herpetological Society andothers challenging the 2006 withdrawal



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of the proposed rule to list the flat-tailedhorned lizard under the Act, the UnitedStates District Court for the District ofArizona (the District Court) grantedsummary judgment in favor of theSecretary of the Interior (TusconHerpetological Societyv. Kempthorne,04CV00075PHXNVW); however,this ruling was appealed to the Court of

Appeals for the Ninth Circuit. In aruling issued on May 18, 2009, theCourt of Appeals for the Ninth Circuitreversed the District Courts rulingwhen it determined that in the contextof the analysis of whether the lizardslost historical range constituted asignificant portion of the species range,the administrative record did notsupport what the Court of Appeals forthe Ninth Circuit viewed as theServices conclusion that flat-tailedhorned lizard populations were stableand viable throughout most of itscurrent range.

On November 3, 2009, the DistrictCourt remanded the 2006 withdrawal tothe Service for further consideration andreinstated the 1993 proposal to list thespecies. The District Court ordered theService to complete this reconsiderationin accordance with the deadlines setforth in 16 U.S.C. 1533(b). On March 2,2010, we published a notice in theFederal Register announcing thereinstatement of the 1993 proposed rule,the reopening of the public commentperiod for 60 days, and the schedulingof public hearings (75 FR 9377). Publichearings were held in Palm Desert,California, on March 23, 2010, and

Yuma, Arizona, on March 24, 2010.

Summary of Factors Affecting theSpecies

Section 4 of the Act (16 U.S.C. 1531et seq.) and the regulations thatimplement the listing provisions of theAct (50 CFR part 424) set forth theprocedures for adding species to theFederal Lists of Endangered andThreatened Wildlife and Plants. Aspecies may be determined to be anendangered or threatened species due toone or more of the five factors describedin section 4(a)(1) of the Act (Factors A

through E).We evaluated threats to the flat-tailedhorned lizard under the five listingfactors in the 1993 proposed rule to listthe flat-tailed horned lizard asthreatened under the Act (58 FR 62624).Subsequent documents in 1997 and2003 withdrawing the proposed rule tolist the species included additionalevaluations (62 FR 37852; 68 FR 331).The 2003 document withdrawing theproposed rule was the mostcomprehensive and the most recent five-factor analysis. The 2006 document

withdrawing the proposed rule (71 FR36745) did not address the five factorsin detail because its scope was limited

by a court order (see Previous FederalActions section). In this document, weuse the best scientific and commercialdata available to evaluate currentpotential threats to flat-tailed hornedlizard and its habitat rangewide per the

five listing factors, and we provide briefsummaries of the 1993 and 2003evaluations for context.

A. The Present or ThreatenedDestruction, Modification, orCurtailment of Its Habitat or Range

For this factor, we evaluated thepresent (current) or threatened(anticipated) impacts that may beaffecting the habitat or range of the flat-tailed horned lizard. This factor doesnot address historical or past actionsthat resulted in destruction,modification, or curtailment of thespecies habitat or range. Past actionsthat destroyed, modified, or curtailedthe species habitat or range are notthreats in and of themselves. Anypersisting ramifications of such pastactions that may be threats to thespecies are addressed under Factor E(other natural or manmade threats),

below. However, for Factor A, we dolook to past actions to inform ourevaluation of potential future threatsaffecting the species habitat or range inthat the history of past actions allows usto predict the likelihood of such actionscontinuing into the foreseeable future.

In the 1993 proposed rule (58 FR

6262562626), we identified historicalflat-tailed horned lizard habitat lossesthat resulted in the curtailment of thespecies range under Factor A. We notedthreats that were current or anticipatedat that time, including agricultural andurban development, off-highway vehicle(OHV) use, geothermal energydevelopment, sand and gravel extractionoperations, military training activities,and construction of roads and utilitycorridors. We also mentioned that flat-tailed horned lizard habitat had beenfragmented, causing isolation ofpopulations (curtailment of the species

range) (see below for additionaldiscussion on fragmentation).Additionally, the 1993 proposed rulealso mentioned gold mining as apotential threat. There are currently nogold mines in flat-tailed horned lizardhabitat, and we are

Documents

FTHL ruling FWS-R8-ES-2010-0008-0042