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Studies of Annual and Seasonal Variations in

Four Species of Reptiles and Amphibians at

Los Alamos National Laboratoy

Los Alamos National Laboratory is operated by the University of Cal~orniafor the United States Department of Energy under contract W-740S-ENG36.

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LosAlamosNATIONAL LABORATORY

Editedby ElectorHinojosa,GroupCIC-IPreparedby TeresaHifetnan,GroupESH-20

An Ajj%mative A&”on/Equal Opportunity Employer

l’his report was prepared as an account of work sponsored by an age-my of the United StifesGovernment. Neifher The Regents of fhe Uniom”ty of Cal~ornia, fhe Unifed Sfafestiernmenf nor any agency thereoj nor any of fheir employees, makes any warranty, expressor implied, or assumes any legal liabili~ or responsibiliQ!fw the accuracy, completeness, orU.WWWSSof any h$mnafiontapparatus, producf, or process dkclosecl, or represents fhaf itsuse would nof inj+ingepn”vafelyownedrights. Rej2renceherein to any spec&iccommerwhlproduct, process, or sm”m by trade name, frademark, manufacturer, or ofherwise, does notneceswn”lywnsh”futeor imply its domement, recommendation, orfmm-ng by The Regentsof fhe Unioers@ of California, the United StafesGavernmenf, or any agency fhereofi Theviews and ~“nions of aufhors expressed herein do nof necessarily stife or rejlecf fhose ofThe Regenfs of fhe Unioersify of Cal@rnia, the Unifed StafesGooernmenf, or any agencyfhereofi Los Alamos National Laboratory strongly supports acdemicfreedom and aresearcher’s righf fo publish; as an institution, howeoer, fhe laborafoy a%esnof endorse theviewpornf of a publication orguaranfee ifs fechnicwlcorrectness.

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LA-13476-MS

UC-908Issued: July 1998 I

Studies of Annual and Seasonal Variations in

Four Species of Reptiles and Amphibians at

Los Alamos National Laboratoy

Esther 1. Nelson

Tim K Ham-mann”

David C. Kkller

Terakne S. Foxx

Mary A. Mullen

LosAlamos

I

NATIONAL LABORATORY

LosAlamos,NewMexico87545

STUDIES OF ANNUAL AND SEASONAL VARIATIONS IN FOUR SPECIES OFREPTILES AND AMPHIBIANS AT LOS ALAMOS NATIONAL LABORATORY

by

. Esther I. Nelson, Tim K. Haammnn, David C. Keller, Teralene S. Foxx, and Mary A. Mullen

ABSTRACTBaseline studies of reptiles and amphibians of the Pajarito wetlands at LosAlamos National Laboratory have been conducted by the Ecology group since1990. With the data gathered from 1990-1997 (excluding 1992), we examinedthe annual and seasonal population changes of four species of reptiles andamphibians over the past seven years. The four species studied are theWoodhouse toad (Zh@ woodhousii), the western chorus frog (Pseudacristriseriata), the many-lined skink (Eunzeces nudtivirgatus), and the plateaustriped whiptail lizard (Cnemidophorus velox). Statistical analyses indicate asignificant change on a seasonal basis for the western chorus frog and the many-lined skink. Results indicate a significant difference in the annual population ofthe Woodhouse toad.

INTRODUCTIONResearch has demonstrated the

importance of reptiles and amphibians innatural ecosystems. Reptiles andamphibians are indicators of generalenvironmental health while aquaticamphibians and snakes are good indicatorsof the health of aquatic systems. Theseanimals are especially sensitive to pollutionand loss of aquatic habitat (Hall 1980).Amphibians and reptiles are also importantin food chains, and they makeup largeproportions of vertebrates in certainecosystems (Bury and Raphael 1983).Because of recent concern for non-gamewildlife, biologists and land managers findthemselves faced with the need to conductstudies and to assess management needs fora group of animals they know little about(Jones 1986). Long-term studies canprovide insight into relationships betweenvariation in environmental factors andvariation in population dynamics (Dunhamand Overall 1994).

Population characteristics of reptilesand amphibians fluctuate from year to yearas well as month to month. In lizards forexample, growth rates have been shown todiffer among years, the variation oftenbeing attributed to differences in rainfall orfood availability between years (Ballingerand Congdon 1980; Dunham 1978). Thevariation among years may be a proximateresponse to variation in rainfall andtemperature (Smith et al. 1995). Influencesby humans, such as disturbance and urbandevelopment of areas, maybe detrimentalto these species. With these factors inmind, we wished to examine whethersignificant changes of populations at theLos Alamos National Laboratory (LANL)Pajarito wetlands have occurred seasonallyor annually.

Pitfall trapping has been employedwidely for surveys of amphibian and reptilediversity and abundance in different habitattypes. Also, pitfall trapping is useful forinvestigating seasonal activity patterns.—Traps can be operated continuously so that

.— —— —-

variations in seasonal activity can bedetected (Bury and Corn 1987).

This report documents the results ofmonitoring reptiles and amphibians usingpitfall trapping at LANL by the EcologyGroup (ESH-20) since 1990. The goal wasto determine seasonal and annual trendsamong reptiles and amphibians of thePajarito wetlands. Seasonal and annualdifferences were analyzed for populationsof the four most common species caught.The results will show whether si~lcantchanges within these four species haveoccurred over the past seven years.

Monitoring generally requiressampling over several years so thatpopulation and community health can beaccurately estimated. This is especiallyneeded in sampling amphibians and reptilesbecause populations fluctuate greatly fromyear to year. Multiyear data collectionallows biologists to determine whichpopulation trends can be attributed tonaturally fluctuating environmentalconditions and which ones should beattributed to other causes (Jones 1986).Studies such as this will allow ESH-20 toprovide pertinent information for LANLmanagement decisions as they pertain toreptiles and amphibians.

Capture data collected from 1990-1997 were aimlyzed for two species ofreptiles, plateau striped whiptail lizard(Cnemidophorus velox) and many-linedskink (lZumeces multivirgatus), and twospecies of amphibians, Woodhouse toad(B&o woodhousii) and western chorus frog(Pseudczcris triseriata), to determinewhether there were significant seasonal orannual fluctuations in populations of thesespecies.

MATERIALS AND METHODSStudy Area

The study area is located withinLkNL’s Technical Area 36, known as the

Pajarito wetlands. The wetlands arelocated 804 m (2655 ft) west of WhiteRock on Pajarito Road (Figure 1). Thestudy site is 127 m (419 ft) wide by 356 m(1175 ft) long.

Vegetation occurring in this areainclude a riparian and a dry uplandassociation (Degenhart et al. 1996). Themajor vegetation in the upland area isApache plume (Fallugia paradoxa),rabbitbrush (Chrysothamnus nauseous),big sage (Artemisia tridentata), and bluegrama (Bouteloua gracilis). Vegetation inthe wetland area include rush (Juncus spp.),willows (Salix spp.), and broad-leavedcattail (Typha latifolia). Pitfall traps weresituated in both upland and riparianvegetation types.

Pitfall TrapsPitfall trapping was the method

used for capturing reptiles and amphibiansat LANL. The study site is divided intotwo areas-denoted as north and south—byan ephemeral stream. Seven small pondsare located adjacent to the north side of thestream.

Drift fences (aluminum flashing)with pitfall traps (large buckets) arecommonly used to inventory and monitorpopulations of amphibians and reptiles(Heyer et al. 1994). Aluminum flashing isplaced in the ground and used to interceptand direct animals into pitfall traps. Lidsare elevated above the traps to provideoverhead protection by attaching uniformlyshaped wooden blocks underneath thecomers. The entire trap system, includingthe aluminum flashing. and buckets, arereferred to as a pitfall trap array.

Nine pitfall trap arrays were placedin the wetland area in 1990, and trappingwas continued on a seasonal basis until1997. All data collected for 1992 wasinvalidated because of predation within thepitfall traps. In 1993, an additional seven

2

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pitfalltrap arrays were added to the studysite at the wetland area. The total numberof pitfall traps (l-gallon buckets) in the 16arrays was 72. In 1997, all pitfall trapswere replaced with 5-gallon buckets. Thetotal number of traps was reduced from 72to 40. Although the number of trapschanged, the traps are in the same locationand encompass the previously occupiedspace.

Traps were opened for the season inlate April and remained open through lateSeptember. They were checked dailyMonday through Friday and closed on theweekends. Trapping days for all years aresimilar. Field technicians responsible forchecking the traps changed on a yearlybasis. Because data collected from 1992are incomplete, we excluded them from ouranalysis.

Animal ProcessingOnce animals were captured, they

were brought back to the laboratory to bemeasured. The mass of the animal wasmeasured in grams with a Mettlerelectronic scale. Then the distance fromthe tip of the rostrum to the vent (snout-vent length) was measured in millimeterswith Mitytoyo electronic calipers. Totaltail length was measured from the vent tothe tip of the tail. If the tail had beendamaged or showed regeneration, then theregenerated portion of the tail was

measuredfromtheanteriorportionofwhere the tail was broken off to the mostposterior portion of the tail. The data wererecorded with date, trap number, andcomments.

AnalysisData for 1990 and 1991 were

adjusted for comparison to the other years’data. The total number of captures (1990and 1991 were calculated separately) weredivided by nine to get an average numberof captures per trap. The resulting numbers

were multiplied by 16to estimate thenumber of animals that would have beencaptured if 16 traps were first present whentrapping began. The adjusted results maynot be whole numbers; results wererecorded to the nearest tenth.

Annual and seasonal fluctuations inthe number of captures were analyzed foreach species using a Kruskal-Wallis non-parametric test. Numbers of captures ofreptiles and amphibians were tested forannual and monthly differences during1990-1997 (excluding 1992).

RESULTSTable 1 lists all of the reptiles and

amphibians captured at the Pajaritowetlands since 1990 (excluding 1992). Thefour reptiles and amphibians of interestcaught on an annual basis at the Pajaritowetlands since 1990 (excluding 1992) havebeen recorded and are included in Table 2.The four reptiles and amphibians of interestcaught on a seasonal basis (excluding 1992)are included in Table 3. Table 4 shows theresults of the Kruskal-Wallis test conductedfor the species of interest by year andmonth.

Woodhouse ToadFigure 2 shows graphs indicating

seasonal and annual fluctuations of theWoodhouse toad. The seasonal graphshows the total number of captures of each

monthoveralloftheyears.Theannualgraph shows the total per year. Theseasonal variation shows a low number oftoads captured (2) for July, while thehighest captured is 16.8 for August. Thegraph displaying annual variation indicatesa low number of captures (l-2 toadscaught) for 1994-1996, and a high numberof captures (27) for 1997.

As indicated in Table 4 the P-valuefor annual variation is 0.05, where the P-value for seasonal variation is 0.64.

TABLE 1. Reptiles and Amphibians Caught at Pajarito Wetlands.*Species 1997 1996 1995 1994 1993 1991** 1990**

Tiger salamander 1 7 1 1 5 53.3 8.9New Mexico spadefoot toad 2 7 0 1 0 1560.8 1.8Woodhouse toad 27 1 2 2 9 7.1 1.8Canyon tree hog o 0 0 0 1 1.8 0Western chorus flog 55 15 4 12 21 48 49.7Short-homed lizard 5 0 0 1 1 0 3.6Prairie lizard* 5 12 3 6 13 3.6 17.8Plateau striped whiptail 83 101 42 73 23 55.1 85.3Many-lined skink 33 37 22 35 49 40.8 81.8Great plains skink o 1 0 1 1 3.6 42.7~lght snake o 1 000 0 0Smoothgreensnake 00001 0 0Western terrestrial g~er snake 5 3 1 9 10 5.3 7.1Prairie rattlesnake 1 0 0 0 0 0 0

*All numbers of animals captured include data ranging from April through October 1990-1997 (excluding 1992).**1990 and 1991 have been adjusted for animals caught in 16 traps vs. 9 traps

TAELE 2. Reptiles and Amphibians Caught Annually at Pajarito Wetlands.*Species 1997 1996 1995 1994 1993 1991** 1990**

Woodhouse toad 27 1 2 29 7.1 1.8Western chorus tlog 55 15 4 12 21 46.2 49.8Plateau striped whiptail 83 101 42 73 23 53.3 78.2Many-lined skink 33 37 22 35 49 39.2 81.8

*AUanimals captured range from May through September**1990 and 1991 have been adjusted for animals caught in 16 traps vs. 9 traps

TAELE 3. Reptiles and Amphibians Caught Seasonally at Pajarito Wetlands 1990-1997 (excluding 1992).*

Species May June July August September

Woodhouse toad 9.1 9 2 16.8 13Western chorus frog 28.3 8.6 28.2 59.5 78.4Plateau striped whiptail 62.6 138.8 101.1 68.7 82.3Many-lined skink 17.9 37.7 59.4 138 38

*1990 and 1991 have been adjusted for animals caught in 16 traps vs. 9 traps

TABLE 4. Results of Kruskal-Wallis Non-Parametric Test for Annual and Seasonal Variation.Species P-value for Annual P-value for SeasonalWoodhouse toad 0.05* 0.64Western chorus frog 0.10 0.04*Plateau striped whiptail 0.16 0.27Many-lined skink 0.74 <0.01**signifiC~tat P = 0.0.5

..——

Seasonalvariation of the Woodhonsetoad

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rt3MAY

IHJUNE

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I14UGUST

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Annual variation of the Woodhousetoad

L•11997

E 1996

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❑ 1991❑ 1990

Figure 2. Seasonal and annual vtiations of the Woodhouse toad.

Western Chorus FrogIrI Fi=we 3 the-graph representing number of captures of 4 in 1995, while in

seasonal variation of the western chorus 1997 a high number of frogs (55) werebog shows a low number of captures being caught. Shown in Table 4 are the P-values8.6 for June and the high number of for annual and seasonal variation. Annualcaptures of 78.4 for September. The graph variation had a P-value of 0.10. Seasonalindicating annual variation shows a low variation had a P-value of 0.04.

Seasonalvariationof thewesternchorusfrog

Annualvariationof thewesternchorusfrog

r❑ 1997

❑ 1995

❑ 19!?5

❑ 1994

■ 1993

❑ 1991

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Figure 3. Seasonal and annual variations of the westemchorus frog.

6

.

Plateau Striped Whiptail June. The annual graph shows 1993 as theFigure 4 shows graphs indicating lowest number of captures (20) and 1996 as

annual and seasonal variations of the the highest number of captures (98).plateau striped whiptail. The smallest Shown in Table 4 are the P-values for ‘number of captures was 62.6 individuals in seasonal and annual variation. The P-valueMay, while the highest number of captures for annual variation is 0.16, the P-value forW% 138.8 in seasonal variation is 0.27.

Seasonalvariationof the plateaustripedWhiptaillizard

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Annualm“ationof theplateaustripedWhi@@ k.ird

120

100

80

60

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Figure 4. Seasonal and annual variations of the plateau striped whiptail lizard.

Many-Lined SkinkFigure 5 shows graphs indicating

annual and seasonal variations in capturesof the many-lined skink. The smallestnumber of skinks captured on a seasonalbasis is 17.9 for May. The greatest numberof skinks captured is 138 -

Sea$oldWlriationofthenmy-linedSkink

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for August. The lowest number of kinksthat were caught on an annual basis was 22in 1995. The greatest number capturedbeing 81.8 was in 1990. As shown in Table ‘4, the P-value for seasonal variation is<0.01. For annual variation the P-value is0.74.

AnnualVariationofthemmy-linedskink

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Figure 5. Seasonal and annual variations of the many-lined skink.

7

DISCUSSIONAnnual variation of the Woodhouse

toad is significant with elevated numbers in1997 compared to 1990-1996. Morejuveniles were caught in 1997 than anyother year. The majority of all juvenilescaught in 1997 were in the months ofAugust and September. Reasons for thismay be attributed to increased precipitationin the late summer months. Gehlbach(1965) suggested that populations innorthwestern New Mexico have a biannualbreeding regime, corresponding to springand summer peaks in precipitation.Currently there are no data to support hissuggestion (Degenhardt et al. 1996).

The populations of western chorusfkogs showed a significant diHerence inAugust and September as compared to ‘other months. This may be attributed to thefact that chorus frogs are much more activeduring the day in late fall. Also, themonsoon season in New Mexico occurs inmid-summer, which may cause the frogs togather in ponds and breed, thus producing .large quantities of young frogs in the fdlmonths.

The many-lined skink has shown asignificant difference in terms of seasonalvariation. Large quantities of juvenileskinks were caught in all of August for allyears sampled. This is probably because of

theemergence ofhatchlings andincreasedactivity for foraging purposes, prior toaestivation during the winter months.

Reptiles and amphibians have beentrapped at the Pajarito wetlands usingpitfall traps since 1990. Animals weretrapped in 1992, but this data could not beused. The project was initiated to monitorthese species as they are affected greatly byenvironmental changes. Through the yearswe have modified our sampling desi=~ andimplemented new techniques to help us

better understand the population dynamicsof these animals. Monitoring generallyrequires sampling over several years so thatspecies and community health can be moreaccurately ewiluated. This is especiallyneeded in sampling amphibians and reptilesbecause populations fluctuate greatly fromyear to year with environmental changes,with respect to precipitation. Data collectedover several years allows biologists todetermine if population trends are resultingfrom naturally fluctuating environmentalconditions or to other causes (Jones 1986).

Literature CitedBallinger, R. E., Congdon, J. D. 1980.Food resource limitation of body growthrates in Sceloporus scalaris(SauriaIguanidae). Copeia 1980(4):921-923.

Bury, R. B., Corn, P.S. 1987. Evaluationof pitfall trapping in northwestern forests:trap arrays with drift fences. Journal ofWildlife Management. 51:1 12–119.

Bury, R. B., Raphael, M.G. 1983.Inventory methods for amphibians andreptiles, in Bell, J. F., Atterbury, T. eds.Renewable resource inventories formonitoring changes and trends:Proceedings of an international conferenc~

1983August15-19;Corvalis,OR. SAF83-14. Corvalis, OR. Society of AmericanForesters: 416-419.

Degenhart, W. Gl, Painter, C. W., Price, A.H. 1996. The amphibians and reptiles ofNew Mexico. University of New MexicoPress.

Dunham, A. E. 1978. Food availability asa proximate factor influencing individualgrowth rates in the iguanid lizard

8

Sceloporus merriami. Ecology 59:770-778.

Dunham, A. E., Overall, K.L. 1994.Population responses to environmentalchange: Life history variation, individual-based models, and the population dynamicsof short-lived organisms. AmericanZoologist 34:382–396.

Gehlbach, F. R. 1965. Herpetology of theZuni Mountains region, northwestern NewMexico. Proc. U. S. Natl. Mus.116(3505):243–332

Hall, R. J. 1980. Effects of environmentalcontaminants on reptiles: A review. U. S.Department of Interior, Fish and Wildlife

Service special scientiilc report 228.Washington, D.C.

Heyer, W. R.,. Domelly, M. A,McDiarmid, R. W., Hayek, L. A. C. andFoster, M. S. eds. 1994. Measuring andmonitoring biological diversi~. Standardmethods for amphibians. Smithsonian Inst.Press, Washington D. C.

Jones, B. K. 1986. Reptiles andamphibians. Pp. 267–290, in Cooperrider,A. Y., R. J. Boyd, and H. R. Stuart, eds.liwentory and monitoring of wildlifehabitat. U.S. Dept. Inter., Bur. LandManage. Service Center. Denver, CO.XViii, 858 pp.

Smith, G. R., Ballinger, R. E., Rose B. R.1995. Reproduction in Sceloporus virgatusfromthe Chiricahua Mountains of

southeastern Arizona with emphasis onannual variation. Herpetological.51(3):342–349.