IDENTIFICATIONAND ASSESSMENTOF WILDLIFEDAMAGE:AN OVERVIEW

Richard A. DolbeerProject LeaderDenver Wildlife Research CenterUSDA-APHIS-Animal Damage ControlSandusky, Ohio 44870

Nicholas R. HollerUnit LeaderAlabama Cooperative Fish and

Wildlife Research UnitUS Fish and Wildlife ServiceAuburn, Alabama 36849

Donald W. HawthorneAssociate Deputy AdministratorUSDA-APHIS-Animal Damage ControlWashington, DC 20090

Introduction

Wildlife management is often thoughtof in terms of protecting, enhancing,and nurturing wildlife populationsand the habitat needed for their well-being. However, many species at onetime or another require managementactions to reduce conflicts with peopleor with other wildlife species. Exam-ples include an airport manager modi-fying habitats to reduce gull activitynear runways, a forester poisoningpocket gophers to increase tree seed-ling survival in a reforestation project,or a biologist trapping an abundantpredator or competing species toenhance survival of an endangeredspecies.

Wildlife damage control is an increas-ingly important part of the wildlifemanagement profession because ofexpanding human populations and

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intensified land-use practices. Concur-rent with this growing need to reducewildlife-people conflicts, public atti-tudes and environmental regulationsare restricting use of some of the tradi-tional tools of control such as toxicantsand traps. Agencies and individualscarrying out control programs arebeing more carefully scrutinized toensure that their actions are justified,environmentally safe, and in the publicinterest. Thus, wildlife damage controlactivities must be based on soundeconomic, ecological, and sociologicalprinciples and carried out as positive,necessary components of overall wild-life management programs.

Wildlife damage control programs canbe thought of as having four parts: (1)problem definition; (2) ecology of theproblem species; (3) control methodsapplication; and (4) evaluation of con-trol. Problem definition refers to deter-

REVENTION AND CONTROL OF WILDLIF

ooperative Extension Divisionstitute of Agriculture and Natural Resourcesniversity of Nebraska - Lincoln

nited States Department of Agriculturenimal and Plant Health Inspection Servicenimal Damage Control

reat Plains Agricultural Councilildlife Committee

mining the species and numbers ofanimals causing the problem, theamount of loss or nature of the con-flict, and other biological and socialfactors related to the problem. Ecologyof the problem species refers to under-standing the life history of the species,especially in relation to the conflict.Control methods application refers totaking the information gained fromparts 1 and 2 to develop an appropri-ate management program to alleviateor reduce the conflict. Evaluation ofcontrol allows an assessment of thereduction in damage in relation tocosts and impact of the control ontarget and nontarget populations andthe environment. Increasingly, empha-sis is being placed on integrated pestmanagement whereby several controlmethods are combined and coordi-nated with other management prac-tices in use at that time.

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E DAMAGE — 1994

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Birds

Damage Assessment

Birds annually destroy many millionsof dollars worth of agricultural cropsin North America. The greatest lossappears to be from blackbirds feedingon ripening corn; a survey in 1981 indi-cated a loss in the United States of330,000 tons (300,000 metric tons)worth $31 million (Besser and Brady1986). Blackbird damage to sunflowercrops in the upper Great Plains stateswas estimated at $5 million in 1979and $8 million in 1980 (Hothem et al.1988). Damage by various bird speciesto fruit crops, peanuts, truck crops,and small grains also can be severe inlocalized areas (Besser 1986). Fish-eating birds can cause major losses atfish rearing facilities. Economic lossesfrom bird strikes to aircraft are per-haps more substantial than those in ag-riculture, at least $20 million annuallyeach for US commercial air carriers(Steenblik 1983) and military aircraft(Merritt 1990).

Unlike most mammals, which aresecretive when causing damage, birdsare often highly visible and their dam-age conspicuous. For this reason, sub-jective estimates often overestimatelosses as much as tenfold (Weather-head et al. 1982). Thus, objective esti-mates of bird damage to agriculturalcrops are important in order to accu-rately define the magnitude of theproblem and to plan appropriate, cost-effective control actions (Dolbeer1981).

To estimate losses due to birds in agri-cultural crops, one must devise a sam-pling scheme to select the fields thatare to be examined and then determinethe plants or areas to be measured inthe selected fields (Stickley et al. 1979).For example, to objectively estimatethe amount of blackbird damage in aripening corn or sunflower field, theestimator should examine at least 10locations widely spaced in the field. Ifa field has 100 rows and is 327 yards(300 m) long, the estimator might walkstaggered distances of 33 yards (30 m)along 10 randomly selected rows (forexample, 0 to 33 yards [0 to 30 m] in

row 9, 34 to 65 yards [31 to 60 m] inrow 20; and so on). In each 33-yard(30-m) length, the estimator shouldrandomly select 10 plants and estimatethe damage on each plant’s ear orhead. Bird damage to corn can be esti-mated by measuring the length ofdamage on the ear (DeGrazio et al.1969) or by visually estimating the per-cent loss of kernels (Woronecki et al.1980) and converting to yield loss peracre (ha). Fruit loss can be estimatedby counting the numbers of undam-aged, pecked, and removed fruits persampled branch (Tobin and Dolbeer1987). Sprouting rice removed by birdscan be estimated by comparing plantdensity in exposed plots with that inadjacent plots with wire bird exclo-sures (Otis et al. 1983). The seeded sur-face area of sunflower heads destroyedby birds can be estimated with the aidof a clear plastic template (Dolbeer1975).

Losses of agricultural crops to birdscan be estimated indirectly throughavian bioenergetics. By estimating thenumber of birds of the depredatingspecies feeding in an area, the percentof the crop in the birds’ diet, the caloricvalue of the crop, and the daily caloricrequirements of the birds, one canproject the total biomass of cropremoved by birds on a daily or sea-sonal basis (White et al. 1985, Weather-head et al. 1982).

Damage Identification

Most bird damage occurs during day-light hours. Thus, observation is thebest way to identify the species caus-ing damage. Presence of a bird speciesin a crop that is receiving damage doesnot automatically prove the speciesguilty, however. For example, large,conspicuous flocks of common grack-les in sprouting winter wheat fieldswere found, after careful observationand examination of stomach contents,to be eating corn residue from the pre-vious crop. Smaller numbers of star-lings were removing the germinatingwheat seeds (Dolbeer et al. 1979).Below, the characteristics of damagefor various groups of birds aredescribed.

Blackbirds and Starlings

The term blackbird loosely refers to agroup of about 10 species of NorthAmerican birds, the most common ofwhich are the red-winged blackbird,common grackle, and brown-headedcowbird. The starling, a European spe-cies introduced to North America inthe late 1800s, superficially resemblesnative blackbirds and often associateswith them. Together, blackbirds andstarlings constitute the most abundantgroup of birds in North America, com-prising a combined population of morethan 1 billion (Dolbeer and Stehn1983).

Gulls

Several gull species have adapted toexisting in proximity to people, takingadvantage of landfills for food. Forexample, the ring-billed gull popula-tion in the Great Lakes region has beenincreasing at about 10% per year sincethe early 1970s (Blokpoel and Tessier1984). Gulls are the most serious birdthreat to flight safety at airports(Solman 1981). They are increasinglycausing nuisance problems in urbanareas by begging for food, defacingproperty, contaminating municipalwater supplies, and nesting on roof-tops. In rural areas, gulls sometimesfeed on fruit crops, consume fish ataquaculture facilities, eat duck eggsand kill ducklings, and compete withthreatened bird species for nest sites.

Blackbird damage to ripening corn,sunflower, and rice can be serious(Dolbeer 1994). Much of this damage isdone in late summer during the milkor dough stage of seed development.The seed contents of corn areremoved, leaving the pericarp or outercoat on the cob. Blackbird damage tosprouting rice in the spring can beimportant in localized areas.

Starling depredations at feedlots inwinter can cause substantial losses(Glahn et al. 1983, Besser et al. 1968).Although contamination of livestockfeed by starling feces is often a concernof farmers, a study indicated this con-tamination did not interfere with foodconsumption or weight gain of cattleand pigs (Glahn and Stone 1984). Star-lings can be serious depredators infruit crops such as cherries and grapes.

Perhaps the greatest problem causedby blackbirds and starlings is their pro-pensity to gather together in large,nocturnal roosting congregations,especially in winter. The noise, fecalaccumulation, and general nuisancecaused by millions of birds roostingtogether near human habitations canbe significant (White et al. 1985).Roosting birds near airports can createa safety hazard for aircraft. Roost sites,if used for several years, can becomefocal points for the fungus that causeshistoplasmosis.

Pigeons and House Sparrows

Pigeons and house sparrows are urbanand farmyard birds whose droppingsdeface and deteriorate buildings.Around storage facilities they consumeand contaminate grain. Pigeons andsparrows may carry and spread vari-ous diseases to people, primarilythrough their droppings (Weber 1979).Droppings allowed to accumulate overseveral years are of particular concern

Crows, Ravens, and Magpies

Crows, ravens, and magpies are well-known predators of eggs and nestlingsin other birds’ nests. In certain situa-tions, these species kill newborn lambsor other livestock by pecking their eyes(Larsen and Dietrich 1970). Magpiessometimes peck scabs on freshlybranded cattle.

Crows occasionally damage agricul-tural crops such as sprouting and rip-ening corn, apples, and pecans. Mostof this loss is localized and minor.Crow damage to apples can be distin-guished from damage by smaller birdsby the deep (up to 2 inches [5 cm]), tri-angular peck holes (Tobin et al. 1989).Roosting congregations of crows intrees in parks and cemeteries some-times cause nuisance problemsbecause of noise and feces.

because they may harbor spores of thefungus that causes histoplasmosis.House sparrows can damage smallgrain crops but this is normally of eco-nomic concern only around agricul-tural experiment stations with smallbut valuable research plots (Royall1969). Sparrows build bulky grassnests in buildings, drain spouts, andother sites where they can cause firehazards or other problems.

Herons, Bitterns, and Cormorants

These species sometimes concentrateat fish-rearing facilities and cause sub-stantial losses (Salmon and Conte1981). Salmon smolts released in riversin the northeastern United States havesuffered heavy depredation by cormo-rants. In recent years, double-crestedcormorants have caused serious lossesat commercial fish ponds in the south-ern United States (Stickley andAndrews 1989). Nighttime observa-tions are sometimes necessary todetermine the depredating speciesbecause herons and bitterns will feedat night.

Hawks and Owls

The raptors most often implicated inpredation problems with livestock(primarily poultry and game farmfowl) are goshawks, red-tailed hawks,and great-horned owls (Hygnstromand Craven 1994). Unlike mammalianpredators, raptors usually kill only onebird per day. Raptor kills usually havebloody puncture wounds in the backand breast. Owls often remove thehead. Raptors generally pluck birds,leaving piles of feathers. Plucked feath-ers with small amounts of tissue cling-ing to their bases were pulled from acold bird that had probably died fromother causes and was simply scav-enged by the raptor. If the base of aplucked feather is smooth and clean,the bird was plucked soon after dying.Because raptors have large territoriesand are not numerous in any one area,the removal of one or two individualswill generally solve a problem.

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Golden Eagles

Golden eagles occasionally kill live-stock, primarily lambs and kids onrange. This predation can be locallysevere in the sheep-producing areasfrom New Mexico to Montana(Phillips and Blom 1988).

Close examination is needed to iden-tify an eagle kill. Eagles have threefront toes opposing the hind toe, orhallux, on each foot. The front talonsnormally leave punctures about 1 to 2inches (2.5 to 5.0 cm) apart in a straightline or small “V” and the wound fromthe hallux will be 4 to 6 inches (10 to 15cm) from the middle toe. In contrast,mammalian predators almost alwaysleave four punctures or bruises fromthe canine teeth. Talon punctures areusually deeper than tooth puncturesand there is seldom any crushing oftissue between the talon punctures. If apuncture cannot be seen from the out-side, skin the carcass to determine thepattern of talon or tooth marks. Oftena young lamb is killed with a singlepuncture from the hallux in the top ofthe skull and the three opposing talonspuncturing the base of the skull or topof the neck (O’Gara 1978, O’Gara1994).

Woodpeckers

Woodpeckers at times cause damageto buildings with wood siding,especially cedar and redwood (Evans

et al. 1983). The birds peck holes tolocate insects, store acorns, or establishnest sites. They also damage utilitypoles. Sapsuckers attack trees to feedon the sap, bark tissues, and insectsattracted to the sap. This feeding cansometimes kill the tree or degrade thequality of wood for commercialpurposes (Ostry and Nicholls 1976).Woodpeckers occasionally annoyhomeowners by knocking on metalrain gutters and stove pipes toproclaim their territories.

Ducks, Geese, and Sandhill Cranes

Damage by ducks and cranes toswathed or maturing small grain cropsduring the fall harvest is a seriouslocalized problem in the northernGreat Plains region (Knittle and Porter1988). Damage occurs from directconsumption of grain and fromtrampling, which dislodges kernelsfrom heads. Losses from tramplingmay be at least double the losses fromconsumption (Sugden and Goerzen1979).

Canada and snow geese that graze onwinter wheat and rye crops can reducesubsequent grain and vegetative yields(Kahl and Samson 1984, Conover1988). Canada geese can also causeserious damage to sprouting soybeansin spring and to standing corn fields inthe autumn. Canada geese haveadapted to suburban environments inthe past 20 years, creating nuisanceproblems around parks and golfcourses through grazing and defeca-tion (Conover and Chasko 1985).

Ungulates (Deer, Elk,Moose)

Damage Assessment

Ungulate damage to various agricul-tural, forestry, and ornamental cropscaused by feeding, trampling, and ant-ler rubbing is an increasing problem.Deer browsing in winter on buds ofapple and other fruit trees can reduceyields the following year (Austin andUrness 1989) or adversely alter thegrowth pattern of tree limbs (Harder1970). Similar browsing on nurseryplants and in Christmas tree planta-tions can reduce or eliminate theirmarket value (Scott and Townsend1985). Browsing of hardwood saplingsand young fir trees in regenerating for-ests can reduce growth rates, misshapetrees, and even cause plantation fail-ures (Crouch 1976, Tilghman 1989).

Damage to trees caused by antler rub-bing can be severe (Scott andTownsend 1985). Small trees (1/2 to 1inch [1.6 to 2.5 cm] in diameter at 6inches [15 cm] above ground) withsmooth bark, such as green ash, plum,and cherry, were preferred for antlerrubbing by white-tailed deer in anOhio nursery (Nielsen et al. 1982).

Objective estimates of economic lossfrom ungulate browsing and rubbingin orchards, nurseries, and reforesta-tion projects are difficult to obtain.Losses in yield or tree value may accu-mulate for many years after damageoccurs and vary with other stresses,including rodent damage, inflicted onthe plants. In Ohio, growers reportedaverage losses to deer in 1983 of $82per acre ($204/ha) for orchards, $89per acre ($219/ha) for Christmas treeplantings, and $108 per acre ($268/ha)in nursery plantings (Scott andTownsend 1985). Losses apparently

are in the millions of dollars annuallyin some US states (Black et al. 1979,Craven 1983b, Connelly et al. 1987).

Deer also feed on various agriculturalcrops, especially young soybean plantsand ripening ears of corn. Hygnstromand Craven (1988) estimated a meanloss of 2,397 pounds of corn per acre(2,680 kg/ha) for 51 unprotected cornfields in Wisconsin. Yield reductions insoybean fields are most severe whenfeeding occurs during the first week ofsprouting (DeCalesta and Schwende-man 1978). Elk in some areas raid hay-stacks and cattle feedlots (Eadie 1954).

Damage Identification

Ungulates do not have an upper set ofincisors. Thus, twigs or plants nippedby these hoofed species do not showthe neat, sharp-cut edge left by mostrodents and lagomorphs, but insteadshow a rough, shredded edge, andusually a square or ragged break.Pearce (1947) observed that deer in theNortheast seldom browse higher than6 feet (1.8 m) from a standing position,but are able to reach up to 8 feet (2.5m) by rearing up on their hind legs.Elk and moose browse to a height ofabout 10 feet (3 m). Deer seldombrowse on branches more than 1 inch(2.5 cm) in diameter. Moose and elkwill gnaw the bark of aspen trees.When male ungulates rub the velvetfrom their antlers, the scarring is gen-erally confined to the trunk area up to3 feet (1 m) high (Pearce 1947).

Rodents and other SmallMammals

Damage Assessment

Rodents and other small mammals areseldom observed in the act of causingdamage, and their damage is frequent-ly difficult to measure. Nonetheless,assessments of damage that have beenmade indicate rodents and nonpreda-tory small mammals cause tremen-dous annual losses of food and fiber inthe United States. Forest animal dam-age in Washington and Oregon wasestimated to total $60 million annuallyto Douglas fir and ponderosa pine andthe potential reduction in the totalvalue of forest resources was esti-mated to be $1.83 billion (Black et al.1979, Brodie et al. 1979). Althoughthese figures include losses attributableto ungulates, rodents and hares areresponsible for much of the damage.

Miller (1987) surveyed forest managersand natural resource agencies in 16southeastern states and estimatedannual wildlife-caused losses, prima-rily by beavers, to be $11.2 million on70 million acres (28.4 million ha). Anadditional $1.6 million was spent tocontrol wildlife damage on this land.Arner and Dubose (1982) estimatedthat economic loss to beavers exceeded$4 billion over a 40-year period on988,000 acres (400,000 ha) in the south-eastern United States. Annual loss inMississippi to nonimpounded timberwas estimated to be $215 million overa period of at least 10 years (Bullockand Arner 1985).

Rats cause substantial losses to sugar-cane. Lefebvre et al. (1978) estimatedannual losses to be about $6 million ($95per acre, [$235/ha]) in one-third of thearea producing sugarcane in Florida.Hawaiian losses were reported to be inexcess of $20 million per year (Seubert1984). Ferguson (1980) estimated that in1978, voles caused losses that approached$50 million to apple growers in the east-ern United States. Losses of forage onrangelands to rodents, rabbits, and haresare also known to be extensive; however,accurate estimates of the monetary lossesare difficult to obtain because of thenature of the damage and the wide area

over which it occurs (Marsh 1985).

Pearson and Forshey (1978) comparedyields of apple trees visibly damagedby voles to those not showing damageto determine the dollar losses in grossreturn per tree. Richmond et al. (1987)determined reductions in growth,yield, and fruit size of apple trees dam-aged by pine vole populations ofknown size maintained in enclosuresaround the trees.

An index of rodent damage to sugar-cane was developed through samplingat harvest to determine the percent ofstalks damaged (Lefebvre et al. 1978).Clark and Young (1986) establishedtransects in corn fields and notedrodent damage to individual seedlingsover a 10-day period. Forage losseshave been estimated by comparingproduction on areas with and withoutrodents (Turner 1969, Foster andStubbendieck 1980, Luce et al. 1981).Sauer (1977) used exclusion cylindersto determine losses of forage toground squirrels. Alsager (1977)described a method to determine for-age production reductions from pocketgopher damage. These methods areuseful in evaluating efficacy of controltechniques. However, loss estimatesmust be converted to accurate assess-ments of dollar loss to enable benefit-cost evaluation of control programs.This conversion is difficult given thevast acreages involved and the vari-ability in rodent populations.

In some situations (for example, timberflooded by beaver, gopher damage toconifer seedlings, vole damage to appletrees), failure to initiate control may meanloss of the entire resource. Thus, poten-tial loss in these situations is equal to thecost of replacement of the resource. Inother situations, control may be necessi-tated irrespective of cost (for example,rats or mice in homes).

These examples illustrate the complex-ity of damage situations and the needfor better damage assessment meth-ods, an area of high priority for futureresearch. Lack of methods for deter-mining damage levels has been a seri-ous impediment to the development ofcost-effective control strategies.

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Damage Identification

Most wild mammals are secretive andnot easily observed; many are noctur-nal. Often the investigator must relyon various signs, such as tracks, trails,tooth marks, scats, or burrows todetermine the species doing the dam-age. Trapping may be necessary tomake a positive identification of smallrodents; frequently, more than onespecies is involved.

Characteristics of the damage mayalso provide clues to the speciesinvolved. In orchards, for example,major stripping of roots is usuallycaused by pine voles, whereas damageat the root collar or on the trunk up tothe extent of snow depth is most oftencaused by meadow voles. In sugar-cane, various species of rats gnawstalks so that they are hollowed out be-tween the internodes but usually notcompletely severed. Rabbits, in con-trast, usually gnaw through the stalks,leaving only the ring-shaped inter-nodes.

Damage to plants can generally begrouped as follows: root damage —pocket gophers and pine voles; trunkdebarking—meadow voles, squirrels,porcupines, wood rats, rabbits, andmountain beavers; stem and branchcutting—beavers, rabbits, meadowvoles, mountain beavers, pocketgophers, wood rats, squirrels, andporcupines; needle clipping—mice,squirrels, mountain beavers, porcu-pines, and rabbits; debudding—redsquirrels and chipmunks. Thesecharacteristics can aid in identificationof the species responsible, but positiveidentification should be made either byspecies-specific signs (tracks, hair,droppings) or by capture ofindividuals.

Armadillos

The armadillo has extended its rangeeastward and northward from Texasand is now found in all Gulf Coaststates and parts of New Mexico, Okla-homa, Kansas, Arkansas, and Missouri(Humphrey 1974). Armadillos feedprimarily on invertebrates obtained byrooting in ground cover. When rooting

takes place in lawns, golf courses, orgardens, economic damage results.There is also concern about the impactof armadillos on forest floor communi-ties within their expanded range (Carr1982).

Armadillo burrows under orchardtrees can cause root damage or exces-sive aeration (Marsh and Howard1990). Nuisance problems result whenarmadillos burrow under structures.Armadillos carry the bacterium thatcauses leprosy in humans, but theirimportance in transmission of the dis-ease to humans has not been deter-mined (Davidson and Nettles 1988).

Bats

Bats, the only mammals capable oftrue flight, eat vast quantities ofinsects. Only a few of the 40 species ofbats found in the United States andCanada cause problems, primarilywhen they form roosts or maternitycolonies in human dwellings or struc-tures. Those most commonly encoun-tered in pest situations are the littlebrown bat, big brown bat, Mexicanfree-tailed bat, pallid bat in the South-west, and Yuma myotis in the West(Greenhall 1982, Frantz 1986). Speciesidentification may be difficult but isimportant because several bat speciesare endangered and protected by stateand federal law. Control operators

unfamiliar with bat identification areurged to seek professional help fromwildlife agencies or universities(Frantz 1986).

The presence of bats in a building isusually evidenced by noise (squeaking,scratching) and by the presence anddistinctive pungent odor of the accu-mulated fecal droppings and urine. Batfeces are readily distinguished fromthose of rodents by odor, insect con-tent, and the ease with which they arecrushed (Greenhall 1982).

Many people are fearful of bats andpanic in their presence. Bats occasion-ally contract rabies, and although fewhuman deaths have resulted from bat-transmitted rabies (Greenhall 1982),contact with a rabid bat or a bite by abat that escapes requires postexposuretreatment of people and pets withoutcurrent vaccinations (Frantz 1986). Thefungal causative organism of histo-plasmosis, a respiratory disease ofhumans, can develop where bat colo-nies are allowed to persist and guanodeposits accumulate. Bats roostingnear airports may be hazardous to air-craft (Kincaid 1975).

Beavers

Beaver damage is easily identified bythe distinctive cone-shaped treestumps resulting from their gnawing,and often by the presence of theirdams and lodges. The latter might notbe present, however, in ponds or reser-voirs, or along swift mountainstreams, where they burrow intobanks. Usually, when beavers areactive in an area, green sticks with thebark freshly peeled off may be found.

Damage caused by beavers resultsfrom feeding behavior (tree cutting)and their efforts to control water levels(dam building). Tree cutting in certainsituations results in selective elimina-tion of preferred tree species, such asaspen and cottonwood, from the vicin-ity (Beier and Barrett 1987). Loss oftimber and crops from flooding is ofmuch greater importance, however,especially in the southeastern UnitedStates where beaver populations haveincreased dramatically as a result of a

decline in trapping due to low peltprices (Woodward 1985). Beaversoften use sticks to plug road culvertsor water-control structures in pondsand reservoirs. Additionally, beaverscan cause extensive damage to leveesand human-made dams by theirburrowing.

Beavers are susceptible to infection byprotozoan parasites (Giardia spp.) thatcan cause gastroenteritis and diarrheain humans. Transmission to humanscan be prevented by use of proper wa-ter treatment measures (Davidson andNettles 1988).

Chipmunks

Occasionally, chipmunks damagegrain fields, garden seeds, flowerbulbs, and plants through burrowingand feeding. They infrequently destroyeggs and nestling birds (Eadie 1954).They can establish residence in or un-der human dwellings. Chipmunkscause reforestation problems by con-suming seeds, seedlings, and the ter-minal buds of older plants, and bycaching seeds, often in large quantities(Marsh and Howard 1990). In parts ofthe western United States, chipmunksare a potential reservoir for plague andare controlled in campgrounds (Marshand Howard 1990). Chipmunks areeasily observed due to their diurnalactivity; their presence can also bedetermined by trapping.

Cotton Rats

The hispid cotton rat, a common spe-cies in the southern United States andin Mexico, is the species of cotton ratmost often causing damage. Two otherspecies have localized occurrences inArizona and New Mexico. Cotton rats

are primarily herbivorous, but theyalso prey on eggs and young ofground nesting birds (Hawthorne1994). They undergo major populationfluctuations. Most damage is a resultof feeding in agricultural crops, espe-cially melons and sugarcane.

Cotton rats are active day and nightand, when abundant, are often ob-served. Their presence is also indicatedby well developed runways throughdense vegetation and the presence ofgrass cuttings 2 to 3 inches (5 to 8 cm)in length placed in piles. Pale greenish-yellow droppings, about 1/2 inch (0.9cm) long and 1/4 inch (0.5 cm) wide,are sometimes present in the runway.Cotton rat sign is similar to that ofvoles but droppings, runways, andclippings of the cotton rat are usuallylarger (Hawthorne 1994). Cotton ratsare often one of several rodent speciescausing damage in crops.

Peromyscus (Deer Mice, White-footed Mice)

The genus Peromyscus is large, and oneor more species is found in all parts ofNorth America. These mice are noctur-nal and active all year. Peromyscuspopulations may show large fluctua-tions. These mice are the most impor-tant seed predators in the PacificNorthwest, causing extensive damagein reforestation efforts (Sullivan 1978).Effects on reforestation have caused ashift to the use of hand-planted seed-lings in many areas. Peromyscus alsocan cause significant losses to cornseedlings in conservation tillage sys-tems but this damage may be offset bytheir consumption of harmful insectsand weed seeds (Johnson 1986, Clark

and Young 1986). Peromyscus mayinvade homes where they eat storedfood and damage upholstered furni-ture or other materials shredded foruse in nest building. They recentlyhave been implicated in the transmis-sion of an often fatal hantavirus tohumans. Infections may occur throughcontact with mouse urine, feces, orsaliva. Trapping with snap or livetraps is the best method to determinethe species present.

Ground Squirrels

Ground squirrels (genus Spermophilus),are important pest species in northcentral and western North America,causing serious losses of tree seeds andemergent seedlings. A careful searchof an area showing damage will revealopened seed hulls and caches. Groundsquirrels can inflict serious damage topastures, rangelands, grain fields,vegetable gardens, and fruit or nutcrops. Their burrows can cause col-lapse of irrigation levees, increase ero-sion, and result in damage to farmmachinery. They are also an importantpredator of waterfowl eggs in the prai-rie pothole region (Sargeant andArnold 1984). They carry several dis-eases transmissible to humans, includ-ing plague; in plague endemic areas,ground squirrel control should becombined with ectoparasite control(Marsh and Howard 1990).

Ground squirrels are diurnal and eas-ily observed (Marsh 1985). They hiber-nate and estivate, and have majordietary shifts during the year (Marsh1985, 1986). Effective control strategiesmust consider these factors.

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Kangaroo Rats

Kangaroo rats are competitors of live-stock on arid western rangelands(Marsh 1985) when present in highpopulations, especially duringdrought. They can also retard recoveryof overgrazed rangelands when cattleare removed (Howard 1994) andspread undesirable shrub species bycaching of seeds (Reynolds andGlendening 1949, Marsh 1985). Kanga-roo rats cause significant damage toalfalfa and corn on irrigated sandysoils by consuming newly plantedseeds and clipping off seedlings(Howard 1994). Sorghum, othergrains, and garden crops can also bedamaged in local areas.

Several species of kangaroo rats areendangered. Kangaroo rats are noctur-nal, but their burrow systems, withaboveground mounds and intercon-necting runways, are readily observed.Snap trap surveys can identify the spe-cies present, provided the damagearea is not within the range of one ofthe species listed as endangered.

Marmots

Marmots (woodchucks), like groundsquirrels, can cause damage to manycrops; forage production may bemarkedly reduced by marmot feedingand trampling (Marsh 1985). Theydamage fruit trees and ornamentalshrubs by gnawing or scratchingwoody vegetation (Bollengier 1994).Their burrows, often located alongfield edges, can cause damage to farmmachinery and injure livestock; whenlocated along irrigation ditches theycan cause loss of water. In suburbanareas, burrows located under build-ings or in landscaped areas causeproblems (Marsh and Howard 1990).The presence of woodchucks is easilydetermined by direct observation ofanimals and burrows. During periodsof forage growth, vegetation around

burrows is noticeably shorter than insurrounding areas. Occupied burrowscan be identified in spring by the pres-ence of dirt pellets ranging frommarble to fist size.

Voles

Voles (genus Microtus), also calledmeadow mice, field mice, and pinemice, cause extensive damage to for-ests, orchards, and ornamentals bygnawing bark and roots (Pearson andForshey 1978, Byers 1984, Pauls 1986,Sullivan et al. 1987, O’Brien 1994). Treeor shrub damage usually occurs undersnow or dense vegetation; the bark isgnawed from small trees near the rootcollar and up the trunk as far as thesnow extends. Voles gnaw throughsmall trees or shoots up to about 1/4inch (0.6 cm) in diameter. Some species(for example, pine vole) also causeextensive damage to root systems; thisdamage may not be detected untilspring when it is reflected in the condi-tion of new foliage. Voles can alsodamage field and garden crops; whenvole populations are high, these lossescan be catastrophic (Clark 1984, Marsh1985). Voles are carriers of plague andtularemia.

Vole populations are subject to large,rapid fluctuations. The presence ofvoles is most easily determined bysearching for their runways and bur-row systems. In orchards these can befound by pulling the grass and otherdebris from the bases of trees toexpose the runways. Burrows of pinevoles are usually subterranean. Gnaw-ing on the trunks and roots of trees isusually less uniform than that of otherrodents. Tooth marks can be at allangles, even on small branches, andmay vary from light scratches to chan-nels 1/10 inch (0.3 cm) wide, 1/12 inch(0.2 cm) deep, and 1/2 inch (1.3 cm)long. In hay crops, runways withnumerous burrow openings, clippedvegetation, and feces, can be located indense vegetation.

Moles

Moles feed primarily on soil inverte-brates, especially earthworms andgrubs (beetle larvae). About 20% oftheir food is plant material, which mayinclude garden vegetables and smallgrains (Silver and Moore 1941). Volesand mice use the burrows of molesand can be responsible for some dam-age attributed to moles (Henderson1994). Burrowing by moles mayreduce production of forage crops byundermining and smothering vegeta-tion, and by exposing root systems todrying. Their surface burrows can alsoplug harvesting machinery and con-taminate hay and silage (Wick andLandforce 1962). Moles can damagelawns and golf greens extensivelythrough burrowing.

The presence of moles can usually bedetected by the mounds of soil thrownup from extensive tunnels dug insearch of food and by the raised soil ofsurface burrows. Mole hills can be dis-tinguished from pocket gophermounds by their more rounded con-tour and the lack of a burrow entranceor soil plug (Eadie 1954).

Mountain Beavers

Mountain beavers cause serious eco-nomic loss by burrowing through andfeeding on garden vegetables, berryplants, and young trees. They usedrainage ditches for burrow sites, andtheir burrows may undermine road-ways.

Mountain beavers are a major factorlimiting reforestation in the Pacificnorthwest (Borrecco and Anderson1980, Evans 1987a). Plantations aremost susceptible to damage for 4 yearsafter planting and when precommer-cially thinned at about 12 to 15 years(Evans 1987a). Mountain beavers clip

seedlings and gnaw saplings and thestems and bark of larger trees.

Mountain beavers normally clip seed-lings through at a 45o angle. On smallseedlings this clipping may be difficultto distinguish from rabbit damage;however, rabbits seldom clip stemslarger than 1/4 inch (0.6 cm) in diam-eter or 20 inches (50 cm) above groundlevel, whereas mountain beavers oftencut stems larger than 1/2 inch (1.3 cm)in diameter and up to 9 feet (3 m)above ground (Lawrence et al. 1961).Mountain beavers leave branch stubs,cut at a 45o angle, protruding from themain stem. The bark of the main stemshows horizontal tooth marks and ver-tical claw marks (Packham 1970). Run-ways and burrows are present in ornear the damaged area.

Muskrats

Muskrats most often cause problemswhere people have created or manipu-lated wetlands or where wetlands bor-der agricultural crops. The mostserious damage results from burrowsin pond dams, levees, and irrigationcanals. The burrow entrance is belowwater level and penetrates theembankment at an upward angle toallow for a room above the water level.Damage is increased when the waterlevel rises and the burrow is extendedhigher to provide a dry chamber,thereby increasing chances of wash-outs and cave-ins. At times, muskratscause severe damage to grain, such asrice, and to garden crops growing nearwater. Muskrats are primarily vegetar-ians, but they will feed on aquatic ani-mals where vegetation is limited(Miller 1994).

Muskrats commonly construct cone-shaped houses projecting 6 inches to 3

feet (15 to 90 cm) above the water sur-face. Muskrat presence is indicated byhouses and burrow entrances. Under-water runs can be observed when thewater is clear or after a winter drawdown of ponds or reservoirs (Miller1994).

Nutria

Nutria are semiaquatic, herbivorousmammals that feed on aquatic plants,roots, seeds, and crops grown close towaterways. The greatest losses fromthis introduced rodent are to sugar-cane and rice, especially in fields adjac-ent to Gulf Coast marshes (LeBlanc1994). Nutria may severely impedecypress regeneration (Conner andToliver 1987). They also damagewooden structures and floatingmarinas.

Nutria presence is evidenced bytracks, droppings, and trails to andfrom the damage area. Nutria alsomay be observed in the damage area.

Pocket Gophers

Pocket gophers cause substantial dam-age to agricultural crops, lawns, range-land, and tree plantings. Gophers feedprimarily on the underground por-tions of plants and trees. Damage oftenis undetected until a tree shows above-ground signs of stress; by then damageis frequently lethal (Cummings andMarsh 1978). Pocket gophers may alsodamage plastic irrigation lines on agri-cultural lands as well as undergroundpipes, cables, and electric wires.

On rangeland, soil disturbance andmound building by pocket gophersresult in increased plant diversity anda replacement of perennial by annualgrasses (McDonough 1974, Foster andStubbendieck 1980, Marsh 1985). Theycan greatly reduce the carrying capac-ity of rangeland for livestock. They canbe a serious pest in alfalfa by feedingon the leaves, stems, and roots (Marsh1985). Gopher mounds can causeequipment breakage and increasedwear on haying machinery. Gophertunnels result in water loss in irrigatedareas (Case and Jasch 1994).

Pocket gophers are a major impedi-ment to reforestation in the westernUnited States (Crouch 1986). Duringwinter pocket gophers often forageabove ground by tunneling in thesnow. Coniferous trees have beenfound debarked to a height of 12 feet(3.5 m) by pocket gophers workingunder the snow (Capp 1976). Gophersalso fill some of the snow tunnels withsoil, thus forming long tubular “casts”that remain after the snow melts.

Pocket gopher presence is easily deter-mined by fan-shaped soil mounds incontrast to the conical mounds ofmoles. Burrow entrances are usuallyplugged. Aboveground debarkinginjuries caused by pocket gophersshow small tooth marks, differingfrom the distinct broader grooves leftby porcupines, and the finely gnawedsurface caused by meadow voles.Gophers will at times pull saplings andvegetation into the burrow.

Porcupines

Porcupines are usually nocturnal andare active all year. During summer,porcupines often feed on succulentplants, including garden and truckcrops in open meadows, fields, andalong the banks of streams and lakes.Greatest damage is caused in winter

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when porcupines feed on the innerbark of trees (Marsh and Howard1990). Girdling in the upper trunk oftrees often results in dead tops (Evans1987b). Basal girdling may occur onseedlings. Porcupines are attracted toanything containing perspiration salt:saddles, harnesses, belts, and toolhandles.

Porcupine damage can be identified bybroad incisor marks on the exposedsapwood. Abundant oblong droppingsabout 1 inch (2.5 cm) long can befound under freshly damaged trees.Clipped twigs and tracks may also befound on snow. Top girdling in pineresults in trees with a characteristicbrushy crown.

Prairie Dogs

Prairie dogs were widespread on theGreat Plains throughout the 1800s andreached peak numbers around 1900after reduction of natural predatorsand establishment of cattle grazing. By1921 the area occupied by prairie dogswas estimated to be 99 million acres(40 million ha). By 1971, followingintensive control efforts, only 1.5 mil-lion acres (0.6 million ha) wereoccupied. Populations have beenexpanding in recent years, commensu-rate with reduced control efforts(Fagerstone 1981).

Prairie dogs damage rangelands andpastures by clipping vegetation forfood and nesting material and byclearing cover from the vicinity of bur-rows (Hygnstrom and Virchow 1994).This activity not only reduces availableforage, but can alter species composi-tion of the vegetation in favor of forbs.

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Competition with cattle does notalways exist, however, and in somesituations beneficial effects of prairiedogs offset competition. Therefore,each conflict situation should be evalu-ated individually (Fagerstone 1981).

Crops planted near prairie dog colo-nies can receive serious damage fromfeeding and trampling. Also, damageto irrigation systems is common, andbadgers digging for these rodentscause even greater damage. The bur-rows and mounds created by prairiedogs can increase soil erosion, causedrainage of irrigation water, and resultin damage to farm implements. Prairiedogs also serve as a reservoir forplague (Hygnstrom and Virchow1994).

Prairie dog colonies provide habitatfor other species, such as the endan-gered black-footed ferret. All lethalcontrol should be preceded by a care-ful survey to ensure that ferrets are notpresent. The Utah prairie dog is athreatened species and should not becontrolled.

Prairie dog colonies are easily identi-fied by the conical mounds aroundburrow entrances and by the presenceof the easily observed animals.

Rabbits and Hares

Rabbits and hares can damage or com-pletely destroy tree plantings, gardens,ornamentals, agricultural crops, andrehabilitated rangeland. In winter, theystrip bark from and debud fruit trees,conifers, and other trees and shrubs(Craven 1994).

Rabbits are known vectors of tulare-mia, which is transmissible to humans,and they may carry larvated eggs ofseveral ascarid roundworms that canproduce disease if accidentallyingested (uncooked) by humans(Davidson and Nettles 1988).

Jackrabbits also damage orchards, gar-dens, ornamentals, and some agricul-tural crops, especially in areas adjacentto rangeland, and most frequentlywhen natural vegetation is dry (Knight1993). Jackrabbit populations show

large fluctuations, and, at times of highdensity, damage to rangeland vegeta-tion and competition with livestockcan be severe.

Trees clipped by rabbits and hareshave a clean oblique knifelike cut onthe stem. Rabbits and hares usuallyclip stems 1/4 inch (0.6 cm) in diam-eter or less at a height not more than20 inches (50 cm) above the ground(Lawrence et al. 1961). Repeated clip-ping will deform seedlings. Rabbitsand hares can often be observed atdamage sites along with their tracks,trails, and droppings.

Tree Squirrels

Tree squirrels may be divided intothree groups: large tree squirrels (gray,fox, and tassel-eared), pine squirrels(red and Douglas), and flying squirrels(northern and southern) (Jackson1994). Squirrels eat plants and fruit,dig up newly planted bulbs and seeds,strip bark and leaves from trees andshrubs, invade homes, and consumebird eggs (Jackson 1994, Hadidian etal. 1987). They cause problems byshorting out transformers and gnaw-ing on power and telephone lines(Marsh and Howard 1990, Hamilton etal. 1987).

Squirrels can often be observed at thedamage site. Damage to conifer seed isindicated by green, unopened conesscattered on the ground under maturetrees and by the accumulated conescales and “cores” at feeding stations.Bark stripping can be observed in treesand bark fragments are often found onthe ground, as are the tips of twigs andsmall branches.

Wood Rats

Wood rats, also called pack rats, brushrats, or trade rats, are attracted to foodsupplies left in buildings and willremove small objects such as spoons,forks, knives, and other items, some-times leaving sticks or other objects “intrade.” They often construct conspicu-ous stick houses in cabins, abandonedvehicles, or in the upper branches oftrees (Marsh and Howard 1990,Salmon and Gorenzel 1994). They willshred mattresses and upholstery.

Wood rats are agile climbers and con-sume fruits, seeds, and green foliageof herbaceous and woody plants(Lawrence et al. 1961). They strip andfinely shred patches of bark from coni-fers and fruit trees to line nest cham-bers (Hooven 1959). They will also clipsmall branches. Their damage may beconfused with that of tree squirrelsand porcupines; however, wood ratsleave a relatively smooth surface witha few scattered tooth marks, and tendto litter the ground beneath the treeless than tree squirrels.

Several subspecies of wood rats areendangered. Local regulations shouldbe checked before control efforts areundertaken.

Commensal Rodents

The three species of commensalrodents (those that live primarilyaround human habitation) are Norwayrats, roof (black) rats, and house mice.These omnivorous rodents consumemillions of bushels of grain each yearin the field, on the farm, in the eleva-tor, mill, store, and home, and in tran-sit. They also waste many moremillions of bushels by contamination.These rodents typically drop 25 to 150pellets and void 1/3 to 2/3 ounce (10to 20 ml) of urine every 24 hours, andconstantly shed fine hairs.

Rats cause extensive damage to sugar-cane in Hawaii and Florida, and roofrats are serious pests in Hawaiian mac-adamia nut plantations. These rodentswill feed on poultry chicks and occa-sionally even attack adult poultry,wild birds, newborn pigs, lambs, andcalves. Health departments annuallyreport hundreds of human babies bit-ten by rats. Many viral and bacterialdiseases are transmitted to humans byrodent feces and urine that contami-nate food and water (Weber 1982).

Gnawing by rodents causes consider-able property damage. Fires are some-times started when rats and micegnaw the insulation of electric wiring.They will also use materials such asoily rags and matches for buildingnests, which can result in fires byspontaneous combustion. Extensivedamage to foundations and concreteslabs is sometimes done when Norwayrats burrow under buildings. Burrowsinto dikes and outdoor embankmentscause erosion.

Signs of commensal rodents are gnaw-ing, droppings, tracks, burrows, anddarkened or smeared areas along wallswhere they travel. Reviews of prob-lems caused by these species andmethods of control are provided byMeehan (1984), Jackson (1987), Bakeret al. (1993), Marsh (1994), and Timm(1994).

Carnivores and otherMammalian Predators

Damage Assessment

Mammalian predators have alwaysbeen a concern to livestock producers.Wade (1982) estimated that the directloss of sheep and goats to coyotes inthe United States ranged from $75 mil-lion to $150 million annually. Pearson(1986), using a summary of other stud-ies and surveys, estimated the loss ofsheep, lambs, and goats to predators(primarily coyotes) to be $68,160,000 inthe 17 western states in 1984. Terrill(1988), using data from all 50 states,reported that annual losses of sheepand lambs to coyotes and other preda-tors ranged from $69 million to $83million in 1985 to 1987. In 1990, 490,000sheep and lambs valued at $21.7 mil-lion and 129,400 goats valued at $5.6million were lost to predators in theUnited States (NASS 1991). In 1991, theNational Agricultural Statistics Serviceestimated that predators killed 106,000cattle and calves in the United States,valued at $41.5 million (NASS 1992).Losses of poultry to predators,although not well documented, arealso thought to be substantial.

Mammalian predators, especially redfoxes, striped skunks, raccoons, andmink, seriously impact waterfowl nest-ing success in small wetland areas sur-rounded by agricultural lands. Astudy in North Dakota indicated nest-ing success of only 8% for mallards onsuch wetlands, half of what wasneeded to sustain the population(Cowardin et al. 1985). The red fox isapparently the most serious waterfowlpredator because it is adept at catchingnesting hens as well as destroying eggs(Sargeant et al. 1984).

Damage Identification

Predation is rarely observed; therefore,the accurate assessment of losses tospecific predators often requirescareful investigative work. The firstaction in determining the cause ofdeath of an animal is to check for signson the animal and around the kill site.Size and location of tooth marks will

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often indicate the species causing pre-dation. Extensive bleeding usually ischaracteristic of predation. Whereexternal bleeding is not apparent, thehide can be removed from the carcass,particularly around the neck, throat,and head, and the area checked fortooth holes, subcutaneous hemor-rhage, and tissue damage. Hemor-rhage occurs only if skin and tissuedamage occurs while the animal isalive. Animals that die from causesother than predation normally do notshow external or subcutaneous bleed-ing, although bloody fluids may be lostfrom body openings (Bowns 1976).Animal losses are easiest to evaluate ifexamination is conducted when thecarcass is still fresh (Wade and Bowns1982).

Animals may not always be killed by athroat attack, but may be pulled downfrom the side or rear. Blood is often onthe sides, hind legs, and tail areas.Calves can have their tails chewed offand the nose may have tooth marks orbe completely chewed by the predatorwhen the tongue is eaten (Bowns1976).

Tracks and droppings alone are notproof of depredation or of the speciesresponsible. They are evidence that aparticular predator is in the area and,when combined with other character-istics of depredation, can help deter-mine what species is causing theproblem.

Badgers

Badgers eat primarily rodents such asmice, prairie dogs, pocket gophers,and ground squirrels. They will alsoprey on rabbits, especially the young.Badgers destroy nests of ground-nesting birds and occasionally killsmall lambs and poultry, parts of

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which they sometimes bury in holesresembling their dens. Dens in cropfields may slow harvesting or causedamage to machinery, and the diggingcan damage earthen dams or dikes(Lindzey 1994).

Badgers usually eat all of a prairie dogexcept the head and fur along theback. This characteristic probablyholds true for most of the largerrodents they eat; however, signs ofdigging near prey remains are the bestevidence of badgers. Badger tracksoften appear similar to coyote tracksbut on close examination they are dis-tinctively “pigeon-toed” with impres-sions from the long toenails apparentin most situations.

Bears

Black and grizzly bears prey on live-stock. Black bears usually kill by bitingthe neck or by slapping the victim.Torn, mauled, and mutilated carcassesare characteristic of bear attacks.Often, the bear will eat the udders offemale prey, possibly to obtain milk.The victim usually is opened ventrallyand the heart and liver are consumed(Bowns and Wade 1980). The intes-tines are often spread out around thekill site, and the animal may be par-tially skinned while the carcass is fedupon. Smaller livestock such as sheepand goats may be consumed almostentirely, and only the rumen, skin, andlarge bones left. Feces are generallyfound within the kill area, and a bed-ding site is often found nearby. Bearsuse their feet while feeding so they donot slide the prey around as docoyotes. If the kill is made in the open,it may be moved to a more secludedspot.

The grizzly has a feeding and killingpattern similar to that of the blackbear. Murie (1948) found that most

cattle are killed by a bite through theback of the neck. Large prey oftenhave claw marks on the flanks orhams. The prey’s back is sometimesbroken in front of the hips where thebear simply crushed it down. Youngcalves are occasionally bitten throughthe forehead.

The presence of bears has stampededrange sheep, resulting in death fromsuffocation or from falls over cliffs. Amarauding bear searching for foodmay also play havoc with garbagecans, cabins, camp sites, and apiaries(Maehr 1983).

Black bear damage to trees can be rec-ognized by the large vertical incisorand claw marks on the sapwood andragged strips of hanging bark. Pole-size trees to small saw timber are pre-ferred. Most bark damage occursduring May, June, and July (Packham1970). After the bark is pulled away,bears will scrape off the cambiumlayer of the tree with their incisorteeth, leaving vertical tooth marks(Murie 1954).

The bear track resembles that of ahuman, but has distinctive clawmarks. The little inside toes often leaveno marks in dust or shallow mud sothe print appears to be four-toed(Murie 1954).

Bobcats and Lynx

These related species occasionally preyon sheep, goats, deer, and pronghorns;however, they more commonly killsmaller animals such as porcupines,poultry, rabbits, rodents, birds, andhouse cats. Bobcats characteristicallykill adult deer by leaping on their backor shoulders, usually when the victimis lying down, and biting them on thetrachea. The jugular vein may be punc-tured, but the victims usually die ofsuffocation and shock. Bowns (1976)

reported that a lamb killed by a bobcathad hemorrhages produced by clawson both sides of the carcass, indicatingthat the bobcat had held the lamb withits claws while biting the neck. Smallfawns, lambs, and other small prey areoften killed by a bite through the top ofthe neck or head (Young 1958). Thehindquarters of deer or sheep areusually preferred by bobcats, althoughthe shoulder and neck region or theflank are sometimes eaten first. Therumen is often untouched. Poultry areusually killed by biting the head andneck (Young 1958); the heads are usu-ally eaten. Also, both species report-edly prey on bird eggs.

Bobcat and lynx droppings are similar;in areas inhabited by both species, thetracks will help determine the respon-sible animal. The lynx has larger feetwith much more hair and the toes tendto spread more than they do on themore compact bobcat tracks.

Feline predators usually attempt tocover their kills with litter (Cook et al.1971). Bobcats reach out 12 to 14 inches(30 to 35 cm) in scratching litter, com-pared to a 35-inch (90-cm) reach of amountain lion (Young 1958). The dis-tance between the canine teeth markswill also help distinguish a lion killfrom that of a bobcat—1 1/2 inches(3.8 cm) for a lion versus 3/4 to 1 inch(1.9 to 2.5 cm) for a bobcat (Wade andBowns 1982).

Coyotes, Wolves, and Dogs

These predators prey on animals rang-ing from big game and livestock torodents, wild birds, and poultry.Coyotes are the most common andmost serious predator of livestock inthe western United States (Wade and

Bowns 1982) and are rapidly becominga problem throughout the east.

Coyotes normally kill livestock with abite in the throat, but they infrequentlypull the animal down by attacking theside, hindquarters, and udder. Therumen and intestines may be removedand dragged away from the carcass.On small lambs, the upper canine teethmay penetrate the top of the neck orthe skull. Calf predation by coyotes ismost common when calves are young.Calves that are attacked, but not killed,exhibit wounds in the flank, hindquar-ters, or front shoulders; often their tailsare chewed off near the top. Deer car-casses are frequently completely dis-membered and eaten (Bowns 1976).

Complaints of pets being killed by coy-otes have increased with urbanization(Howell 1982). Also, the increase in thenumber of reported human attacks hascreated additional concern for urbandwellers. Avocado producers usingdrip irrigation systems report thatcoyotes chew holes in plastic pipe anddisrupt irrigation (Cummings 1973).Coyotes damage watermelons by bit-ing holes through the melons and eat-ing the centers out; raccoons, on theother hand, make small holes in themelons and scoop the pulp out withtheir front paws. Coyotes will alsodamage other fruit crops.

Wolves prey on larger ungulates suchas caribou, moose, elk, and cattle.Wolves usually bring down these ani-mals by cutting or damaging themuscles and ligaments in the back legsor by seizing the victim in the flanks.Slash marks made by the canine teethmay be found on the rear legs andflanks. The downed animals usuallyare disembowelled.

Domestic dogs can be a serious prob-lem to livestock, especially to sheeppastured near cities and suburbs. Dogsoften attack the hindquarters, flanks,and head of livestock. They rarely killas effectively as coyotes (Green et al.1994). Normally, little flesh is con-sumed. Dogs are likely to wound theanimal in the neck and front shoulders;the ears often are badly torn. Attackingdogs often severely mutilate the victim(Bowns and Wade 1980).

Coyote and dog tracks are similar butdistinguishable. Dog tracks are roundwith the toes spread apart. Toenail marksare usually visible on all toes (Dorsett1987). Coyote tracks are more rectangu-lar and the toes are closer together. If anytoenail marks show, they are usually ofthe middle toes. Also, coyote tracksappear in a straight line whereas those ofa dog are staggered.

Foxes

Gray and red foxes feed primarily onrabbits, hares, small rodents, poultry,birds, and insects. They also consumefruits. The gray fox eats fish, a prey sel-dom eaten by the red fox. Gray andespecially red foxes kill young live-stock, although poultry is their morecommon domestic prey. Foxes usuallyattack the throat of lambs and birds,but kill some by multiple bites to theneck and back (Wade and Bowns1982). Normally, foxes taking fowlleave behind only a few drops of bloodand feathers and carry the prey awayfrom the kill location, often to a den.Eggs are usually opened enough to belicked out. The shells are left beside thenest and are rarely removed to theden, even though fox dens are notedfor containing the remains of theirprey, particularly the wings of birds.

Einarsen (1956) noted that the breastand legs of birds killed by foxes areeaten first and the other appendagesare scattered about. The toes of the vic-tims are usually drawn up in a curledposition because of tendons pulledwhen the fox strips meat from the legbone. Smaller bones are likely to besheared off. The remains are often par-tially buried.

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Like other wild canids, foxes willreturn to established denning areasyear after year. They dig dens inwooded areas or open plains. Hollowlogs are also used. Dens may be identi-fied by the small doglike tracks or byfox hairs clinging to the entrance. Thegray fox is the only fox that readilyclimbs trees, sometimes denning in ahollow cavity.

Hogs

Problems associated with feral or wildhogs have increased across the south-ern United States. Rooting and wal-lowing by wild hogs can damageagricultural crops and timber and alsodamage farm ponds and irrigationdikes (Barrett 1994). Wild hogs alsofeed on young sheep and goats in cer-tain parts of the United States. Thelosses are difficult to determine attimes because almost the entire carcassis either eaten or carried off and theonly evidence may be tracks and bloodwhere feeding occurred (Wade andBowns 1982).

Tracks of adult hogs resemble thosemade by a 200-pound (90-kg) calf. Insoft ground dewclaws will show onadult hog tracks (Barrett 1994).

Mountain Lions

Often called cougar or puma, this largefeline preys on deer, elk, and domesticstock, particularly horses, sheep, goats,and cattle. It also eats rodents andother small mammals, when available.In one situation, according to Young(1933), a lone lion attacked a herd ofewes and killed 192 in one night. How-ever, 5 to 10 sheep killed in a singlenight is more typical (Shaw 1983).

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Mountain lions, having relatively short,powerful jaws, kill with bites inflictedfrom above, often severing the vertebralcolumn and breaking the neck. They alsokill by biting through the skull (Bowns1976). Lions usually feed first on thefront quarters and neck region of theirprey. The stomach is generallyuntouched. The large leg bones may becrushed and the ribs broken. Many times,after a lion has made a kill, the prey isdragged or carried into bushy areas andcovered with litter. A lion might returnto feed on a kill for three or four nights.They normally uncover the kill at eachfeeding and move it from 11 to 27 yards(10 to 25 m) to recover it. After the lastfeeding the remains may be left uncov-ered, and a search of the area mightreveal previous burial sites (Shaw1983).

Adult lion tracks are approximately4 inches (10 cm) in length and 4 1/4inches (11 cm) in width; they have fourwell-defined impressions of the toes atthe front, roughly in a semicircle. Lionshave retractable claws; therefore, noclaw prints will be evident. Theuntrained observer sometimes con-fuses large dog tracks with those of thelion; however, dog tracks normallyshow distinctive claw marks, are lessround than lion tracks, and have dis-tinctly different rear pad marks.

Opossums

Opossums are omnivorous and occa-sionally eat fish, crustaceans, insects,mushrooms, fruits, vegetables, eggs,and carrion. They will also raid poul-try houses. The opossum usually killsone chicken at a time, often maulingthe victim (Burkholder 1955). Eggs willbe mashed and messy, the shells oftenchewed into small pieces and left inthe nest. Opossums usually begin feed-ing on poultry at the cloacal opening.

Young poultry or game birds are con-sumed entirely and only a few wetfeathers left.

Raccoons

Raccoons eat mice, small birds, snakes,frogs, insects, crawfish, grass, berries,acorns, corn, melons — the list isalmost endless. Garbage cans anddumps can be a major source of foodin urban areas. Field crops or gardensnear wooded areas may suffer severedamage from raccoons. Ripening cornis frequently eaten and much is wasted(Conover 1987). They raid nestingcavities of birds (Lacki et al. 1987).They will on occasion kill small lambs,usually by chewing the nose.

Occasionally, raccoons enter poultryhouses and take several birds in onenight. The breast and crop can be tornand chewed, and the entrails some-times are eaten. There may be bits offlesh near water. Eggs may beremoved from poultry or game birdnests and eaten away from the nest.Rearden (1951) found that eggshellswere located within 28 feet (9 m) of thenest.

The raccoon leaves a distinctive five-toed track that resembles a smallhuman hand print. Tracks are usuallypaired, the left hind foot beside theright forefoot (Murie 1954). Raccoonand opossum tracks can be difficult todistinguish in soft sand where toes donot show.

Skunks

Insects, particularly grasshoppers,beetles, and crickets, make up a largeportion of the skunk’s diet. Skunksusually dig small cone-shaped holes inlawns, golf courses, and meadows insearch of beetle larvae. A commoncomplaint of objectionable odor occurs

Acknowledgments

This chapter was adapted with permission fromR. A. Dolbeer, N. R. Holler, and D. W.Hawthorne. 1994. Identification and Control ofWildlife Damage. T. A. Bookhout, ed. Researchand management techniques for wildlife andhabitats. The Wildlife Society, Bethesda,Maryland. 1994.

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Barrett, R. H. 1994. Wild pigs. Pages D65-D70 inS. E. Hygnstrom, R. M. Timm, and G. E.Larson, eds. Prevention and control ofwildlife damage. Univ. Nebraska Coop. Ext.Lincoln.

Beier, P., and R. H. Barrett. 1987. Beaver habitatuse and impact in Truckee River basin,California. J. Wildl. Manage. 51:794-799.

Besser, J. F. 1986. A guide to aid growers inreducing bird damage to US agriculturalcrops. Denver Wildl. Res. Cent. Bird DamageRes. Rep. No. 377. 91pp.

Besser, J. F., and D. J. Brady. 1986. Bird damageto ripening field corn increases in the UnitedStates from 1971 to 1981. US Fish Wildl.Serv., Fish and Wildl. Leafl. 7. Washington,DC. 6pp.

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when skunks take up residence underbuildings. Skunks may depredate bee-hives.

Skunks kill few adult birds, but areserious nest robbers (Einarsen 1956).Eggs are usually opened at one end;the edges are crushed as the skunkpunches its nose into the hole to lickout the contents (Einarsen 1956, Davis1959). The eggs may appear to havebeen hatched, except for the edges.When in a more advanced stage ofincubation, eggs are likely to bechewed in small pieces. Eggs may beremoved from the nest, but rarelymore than 3 feet (1 m) away.

Most rabbit, chicken, and pheasantcarcasses found at skunk dens are car-rion that have been dragged to the densites (Crabb 1948). When skunks killpoultry, they generally kill only one ortwo birds and maul them consider-ably. Crabb (1941) observed that spot-ted skunks help control rats and micein grain storage buildings. They killthese rodents by biting and chewingthe head and foreparts; the carcassesare not eaten.

Inhabited dens can be recognized byfresh droppings containing undigestedinsect parts near the mound or hole.Hair and rub marks also may bepresent. Dens usually have a charac-teristic skunk odor, although the odormay not be strong.

Weasels and Mink

Weasels and mink have similar feed-ing behaviors, killing prey by bitingthrough the skull, upper neck, or jugu-lar vein (Cahalane 1961). When theyraid poultry houses at night, they oftenkill many birds, eating only the heads

of the victims. Predation by rats usu-ally differs in that portions of the bodyare eaten and carcasses are draggedinto holes or concealed places.

Errington (1943) noted that mink,while eating large muskrats, make anopening at the back or side of the neck.As the mink eats away flesh and piecesof the adjacent hide, the ribs, head, andhindquarters are pulled out throughthe same hole and the animal isskinned. McCracken and Van Cleve(1947) noted similar feeding behaviorby weasels eating small rodents.

Teer (1964) observed that blue-wingedteal eggs destroyed by weasels werebroken at the ends and had openings1/2 to 3/4 inch (1.5 to 2.0 cm) indiameter. Close inspection of shellremains frequently will disclose finelychewed edges and tiny tooth marks(Rearden 1951).

Weasels den in the ground (forexample, in a mole or pocket gopherburrow), under a barn, in a pile ofstored hay, or under rocks. Mink digdens approximately 4 inches (10 cm) indiameter into banks. Mink also usemuskrat burrows, holes in logs andstumps, and other natural shelters.

Domestic Cats

Domestic cats rarely prey on anythinglarger than ducks, pheasants, rabbits,or quail. Einarsen (1956) noted themessy feeding behavior of these ani-mals. Portions of their prey are oftenstrewn over several square yards (m)in open areas. The meaty portions oflarge birds are consumed entirely,leaving loose skin with feathersattached. Small birds are generallyconsumed and only the wings andscattered feathers remain. Cats usuallyleave tooth marks on every exposed

bone of their prey. Nesting birds areparticularly vulnerable to cat preda-tion. In areas managed for game birdsor waterfowl production, vagrant catcontrol is almost a necessity. Unliketheir native cousins, domestic cats areobserved readily in the daytime,although feral cats are often extremelywary.

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EditorsScott E. HygnstromRobert M. TimmGary E. Larson