Cougar Population Dynamics in Southern UtahAuthor(s): Frederick G. Lindzey, Walter D. Van Sickle, Bruce B. Ackerman, Dan Barnhurst,Thomas P. Hemker and Steven P. LaingSource: The Journal of Wildlife Management, Vol. 58, No. 4 (Oct., 1994), pp. 619-624Published by: Wiley on behalf of the Wildlife SocietyStable URL: http://www.jstor.org/stable/3809674 .

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COUGAR POPULATION DYNAMICS IN SOUTHERN UTAH

FREDERICK G. LINDZEY, Wyoming Cooperative Fish and Wildlife Research Unit, Box 3166, University Station, Laramie, WY 82071

WALTER D. VAN SICKLE, Wyoming Cooperative Fish and Wildlife Research Unit, Box 3166, University Station, Laramie, WY 82071

BRUCE B. ACKERMAN,' Utah Cooperative Fish and Wildlife Research Unit, UMC 52, Utah State University, Logan, UT 84321 DAN BARNHURST,2 Utah Cooperative Fish and Wildlife Research Unit, UMC 52, Utah State University, Logan, UT 84321 THOMAS P. HEMKER,3 Utah Cooperative Fish and Wildlife Research Unit, UMC 52, Utah State University, Logan, UT 84321 STEVEN P. LAING,4 Wyoming Cooperative Fish and Wildlife Research Unit, Box 3166, University Station, Laramie, WY 82071

Abstract: We monitored size and composition of a southern Utah cougar (Felis concolor) population during 1979-87 to document the dynamics of this unhunted population and to test the hypothesis that cougars would regulate their density at a level below that set by prey abundance alone (Seidensticker et al. 1973). We captured cougars when detected during ongoing searches for sign in the study area. Resident adult cougar density remained relatively constant (0.37/100 km2) for the first 7 years but increased slightly in the last 2 years. Mule deer (Odocoileus hemionus), the cougar's primary prey, increased over the 9 years, but magnitude of this increase was unknown. Results supported the hypothesis that cougar density is set by environmental features other than prey abundance alone. Adult resident females bred as young as 17 months and produced litters that averaged 2.4 kittens at an interval of 24.3 months.

J. WILDL. MANAGE. 58(4):619-624

Key words: cougar, Felis concolor, mountain lion, population dynamics, reproduction, Utah.

Management agencies face demands for ad- ditional cougar-hunting opportunities, relief from cougar depredation on domestic livestock, and challenges of their cougar management programs from the general public. Information available to managers comes primarily from short-term cougar research efforts often con- ducted on populations exploited by hunting. Hornocker's (1970) and Seidensticker et al.'s (1973) research in Idaho provided insight into the long-term dynamics of a cougar population. They hypothesized that cougar populations were

capable of regulating their density and that this

density would ultimately be established on the basis of factors other than prey density. Sex ra- tios in most cougar populations appear to favor females, but age composition often differs among populations (Seidensticker et al. 1973, Shaw 1977, Ashman et al. 1983, Logan 1983, Hemker et al. 1984, Hopkins et al. 1986).

We monitored size, composition, natality, and

emigration in an unhunted cougar population in southern Utah to evaluate the hypothesis that cougar populations could regulate their density and to enable comparisons of population attri- butes with those of other cougar populations. We concurrently monitored mule deer popu- lation size because of its potential influence on cougar population dynamics.

We thank N. H. Hancock, D. Bunnell, J. A. Roberson, and J. W. Bates for coordinating the project through the Utah Division of Wildlife Resources (UDWR). Primary funding was pro- vided by the UDWR and administered by the Wyoming and Utah Cooperative Fish and Wild- life Research units. T. Rettberg and V. Judkins served as pilots. A. J. Button (deceased), W. W. Button, C. S. Mecham, and M. C. Mecham pro- vided field assistance and functioned as hounds- men.

STUDY AREA The 4,500-km2 study area was located in Gar-

field and Kane counties in south-central Utah. We used a core area of 1,900 km2 for population analyses (population study area). The study area was bordered on 3 sides by relatively treeless, open areas that likely would not support cougars (Laing and Lindzey 1991). Elevation in the area ranged from 1,350 to 3,335 m. Climate was characterized by moderately heavy snowfall in

' Present address: Florida Department of Natural Resources, Florida Marine Research Institute, 100 8th Avenue S.E., St. Petersburg, FL 33701.

2 Present address: Utah Division of Wildlife Re- sources, Vernal, UT 84078.

3 Present address: Idaho Department of Fish and Game, P.O. Box 25, Boise, ID 83707.

4 Deceased.

619

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620 COUGAR POPULATION DYNAMICS * Lindzey et al. J. Wildl. Manage. 58(4):1994

winter, hot (Jul 9 = 24.5 C), dry summers with occasional intense thunderstorms, and mild spring and fall seasons. Annual precipitation, primarily snowfall, averaged 18 cm at lower elevations and 60 cm on high elevation plateaus (Tew 1972). Vegetation and land uses in the area are described in Lindzey et al. (1992).

Mule deer, the most common wild ruminant, occurred at population levels (about 5,000) be- low those of the 1960s (Hemker 1982). Elk (Cervus elaphus) were introduced to the area in 1977 and numbered 200-400 during the study. Other potential cougar prey animals present in- cluded black-tailed jackrabbit (Lepus califor- nicus), snowshoe hare (L. americanus), moun- tain cottontail (Sylvilagus nuttallii), desert cottontail (S. audubonii), and smaller rodents.

METHODS The area was closed to cougar hunting in 1979

to facilitate the study, but cougar hunting con- tinued adjacent to the study area, and the study area was hunted and trapped for other animals. We conducted experimental hunts during win- ters 1982-83 and 1983-84, removing 2 young, nonresident cougars from the area (Barnhurst 1986).

Monitoring for population analyses began in

January 1979 and ended in 1987, during a re- moval experiment (Lindzey et al. 1992). We captured cougars using methods similar to those described by Hornocker (1970) and Hemker et al. (1984). We initially located cougars by searching roads and trails for tracks and using trained dogs while riding horses or walking off the roaded portions of the study area. When a cougar was treed we climbed the tree to within 5 m of the cougar to allow safe positioning of a projectile syringe fired from a CO2-powered pis- tol. We used a 1.00:0.15 mixture of ketamine HCI and xylazine HCI for immobilization (Clark et al. 1979). We tattooed ears with an identifi- cation number and attached numbered ear tags. We attached a collar containing a motion-sen- sitive radio transmitter to each cougar. Kittens (<1 yr old) were fitted with either expandable, drop-off radio collars similar to those described by Garcelon (1977) or radio collars simply tied with cotton string, which allowed the collar to fall off when the string rotted. We fitted older kittens with adult-sized collars. There was little neck growth in females after 6 months of age. Beginning in 1980, we surgically removed a toe

(initially front, later hind) from adult, resident cougars to enable track identification.

We used dental (Ashman et al. 1983) and physical characteristics (Eaton and Velander 1977) and documented birth dates to determine ages of captured cougars. We classified cougars as resident, transient, or juvenile. Residents were adult cougars (>1.5 yr old) that showed site attachment (continuous use of a predictable area for >6 months). We classified immigrants and independent young of the study population as transient until they met our definition of resi- dent. Consequently, a cougar could be classified transient 1 year and resident the next year. Transients did not use predictable areas and did not breed. We classified progeny of the resident population as juvenile while they were still as- sociated with their mothers.

We attempted to locate all radio-collared cou- gars at least once a week from a fixed-wing aircraft. Telemetry flights covered, as necessary, the entire study area and adjacent areas. We also located selected cougars several times a week from the ground to obtain more detailed infor- mation on movements, intraspecific associations, and activity patterns. We monitored move- ments of resident females for patterns that would suggest they had kittens (e.g., frequent return to the same area). We approached females sus- pected of having kittens without dogs or cau- tiously with less aggressive, younger dogs to lo- cate the litter. When it was necessary to use dogs to locate a suspected litter, we waited until the litter was about 3 months old, an age at which kittens could escape dogs if necessary.

We determined size and composition of the study population by systematically searching the population study area throughout the year, with and without dogs, for evidence of new cougars (Seidensticker et al. 1973, Hemker et al. 1984). We searched all areas, including those occupied by cougars, and searched the remainder of the study area as well but with less intensity. We captured cougars when detected. One to 4 per- sonnel, including a full-time houndsman, were present on the study area. Movement records of radio-collared cougars and tracks of cougars marked by surgical removal of a toe enhanced sign interpretation. Observations of cougars or their sign by persons working and trapping in the area augmented our observations. Each win- ter (Jan-Mar) we made population estimates, on the basis of the number of radio-collared cou- gars and their offspring and the number of doc-

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J. Wildl. Manage. 58(4):1994 COUGAR POPULATION DYNAMICS * Lindzey et al. 621

umented, but unmarked, cougars present in the area.

Mule deer abundance was indexed annually with pellet group transects on the winter range (Neff 1968, Ackerman 1982). We used 10-m2 circular plots spaced 10 paces apart along tran- sects (usually 50 plots/transect). Although we did not use permanent plots we fixed starting point and direction for each transect. We sur- veyed transects between May and August. We established 5,176 plots on 94 transects by the end of the third year. After the third year, we reduced the number of transects to 46 (2,490 plots) that adequately represented the winter range of deer within the area (Hemker et al. 1984). These 46 transects were subsequently sur- veyed each year except in 1983. We calculated an index to mule deer abundance by dividing the number of pellet groups found on these 46 transects each year by number of plots, multi- plying this number by 100, and then dividing the product by the estimated number of days deer were on winter range. We estimated time deer spent on the winter range each year from field observations. We also used success of mule deer hunters and number of male deer har- vested as indices of mule deer population trend (Utah Div. Wildl. Resour. 1990). The deer herd unit used in these analyses (51B; Utah Div. Wildl. Resour. 1990) included about 90% of the study area. Some deer that summered within this unit likely migrated northward into the adjacent herd unit during winter and thus were not sampled with pellet-group transects. We had no indica- tion, however, that the proportion of the pop- ulation that migrated out of the herd unit (51B) differed among years.

We measured annual change in mule deer population indices by fitting straight lines through their natural logarithms plotted against years. We examined the relationship between deer and cougar numbers with Spearman rank order correlation analyses.

RESULTS We monitored 72 radio-collared cougars dur-

ing the study for an average of 16.9 months (SD = 17.3) each. Because some female progeny es- tablished home ranges on the study area, lin- eages of 3 of the original females were present throughout the study. We documented fourth filial generations in 2 female lineages and a third filial generation in another.

Table 1. Size and composition of a southern Utah cougar population estimated from captures, telemetry records, and sign of unmarked cougars, 1979-87.

Adult residents

Tran- Total Yeara M F Total Juv sients cougars

1979 2 6 8 7 0 15 1980 1 6 7 14 1 22 1981 1 5 6 11 2 19 1982 1 7 8 3 0 11 1983 0 7 7 6 1 14 1984 1 5 6 9 4 19 1985 1 6 7 5 10 24b 1986 4 6 10 9 6 25 1987 4 8 12 8 4 26b

a Annual survey period Jan-Mar. b Two independent cougars of unknown status known to be present.

Size of the adult resident segment of the cou- gar population changed little over the first 7 years but increased the last 2 (Table 1). This increase resulted from immigration and estab- lishment of males and an increase of 1 above the long-term average of 7 adult females. Num- bers of transients and kittens varied annually, but there was no apparent trend in kitten num- bers that would suggest synchronous breeding. Three adult females (1 each in 1983, 1986, and 1987) and 5 kittens died during the study from apparent capture-related injuries.

Natality We observed 31 litters between 1979 and 1989

(we monitored the population for 2 additional years during the removal experiment; Lindzey et al. 1992). Litters were born in each month except December, January, and March. A birth peak in late summer and fall was apparent, with 6 litters born in August, 7 in September, and 11 in October. Other months had 1 birth, except June during which there were 2 births. Average size of 26 litters where we felt we had found all kittens was 2.4 (SD = 0.8). Litter size ranged from 1 (n = 4) to 4 (n = 1), with litters of 2 (n = 9) and 3 (n = 12) most common. Sex ratio of kittens in 14 litters from which all kittens were sexed favored males (1.31 M:1.00 F).

Six females that were marked as kittens and remained to establish home ranges on the area first gave birth at a mean age of 26 months (SD = 4.5, range 20-34). Assuming a 92-day gesta- tion period (Eaton and Velander 1977), average age at first breeding for these females was 23

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622 COUGAR POPULATION DYNAMICS o Lindzey et al. J. Wildl. Manage. 58(4):1994

months (SD = 4.5), and the earliest a female successfully bred was 17 months.

We documented interval between successive litters on 11 occasions. On 3 occasions (12-, 13-, and 16-month intervals) we felt all kittens in the first litter had died before 1 year of age, and the female had apparently bred again. On an- other occasion, during the harvest experiment (Lindzey et al. 1992), we translocated a female between successive litters (29-month interval). The remaining 7 intervals, where

> 1 kitten sur- vived > 1 year, averaged 24.3 months (SD = 6.8, range 19-40).

Dispersal Of 15 progeny of the population that carried

functioning radio collars at 16 months of age, all 5 males dispersed from the area while 7 of the 10 females remained and established home

ranges. Average straight-line distance from the natal ranges of the 5 males to where they were killed was 123 km (SD = 75, range 39-241 km). They died an average of 9.8 months (SD = 6.5) after leaving the area. One of the 2 females that dispersed was killed 66 km from her natal range when she was 2.5 years old (11-12 months post- dispersal) and the other 47 km distant when she was 12.5 years old.

Mule Deer Population The pellet group index, hunter success, and

number of male mule deer harvested suggested an increasing mule deer population over the

study. Hunter success in 1986 was over twice what it had been in 1978, and deer harvest was 3 times as great (Utah Div. Wildl. Resour. 1990). Pellet group index, harvest, and hunter success increased annually an average of 16.0, 1.9, and 1.3%, respectively. The relationship between the pellet group index and cougar numbers over the

study was weak (r, = 0.602, P < 0.005). Deer and cougar numbers were more poorly related over the first 7 years (r, = 0.216, P >0.50).

DISCUSSION The resident adult segment of the Boulder-

Escalante cougar population remained relative- ly constant in size over the first 7 years of the study. Sufficient numbers of transients were present over this period to have provided for growth of the population had they established residency. Removal of 2 young, transient cou- gars from the population during winters 1982- 83 and 1983-84 likely had little influence on

population dynamics because of the abundance of transients in the population during the 7 years. The increase in resident adults in the last 2 years (1986-87) resulted from recruitment of immi-

grating males and an increase of 1 female over the long-term average of 7 and brought the adult sex ratio (1987 = 1 M:2 F) close to that observed in other populations (1:2, Seidensticker et al. 1973; 1:2 = min. and 1:3 max., Logan 1983). Resident adult numbers returned to the higher 1987 level, with the possible exception of 1 male, 9 months after the population was experimen- tally reduced by 27%. With the exception of 1 female, resident adults were at the 1987 level 2

years later (Lindzey et al. 1992), suggesting the resident adult segment of the population had stabilized at this higher level.

We believe that continual reconnaissance of the area with and without trained dogs, our

ability to identify marked residents from tracks even if their transmitter had failed, and moni-

toring of radio-collared cougars enabled accu- rate annual enumeration of resident adults. Only once did we capture a female of an age that would indicate we may have missed her the

previous year. However, we undoubtedly did not capture all transients that were present dur-

ing a given year. We found tracks of small, unmarked cougars only once despite increased search efforts following the initial sighting, sug- gesting the cougar had simply moved through the study area. Young cougars radiocollared as transients, but not independent progeny of study area residents, occasionally left the area. Kitten numbers also may have been underestimated in some years because we did not always find a litter when a female's movement pattern or her earlier association with a male suggested she had

young. Reproduction remained high during the study,

undoubtedly facilitated in part by the popula- tion's regulation of its own density. Average lit- ter size (2.4) in the population was only slightly lower than the fetal litter size of 2.8 reported by Robinette et al. (1961) and the captive cougar litter size of 2.6 documented by Eaton and Ve- lander (1977). Litter size at birth on our study area may actually have been larger than 2.4 because we did not investigate about 65% of the litters until they were >3 months old (Hemker et al. 1986), and some kittens may have died by this time. The interval we observed between litters (24.3 months) was also similar to that ob- served in other cougar populations (Anderson

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J. Wildl. Manage. 58(4):1994 COUGAR POPULATION DYNAMICS * Lindzey et al. 623

1983). The shorter interval between litters of the 3 females that had lost their litters before kittens were 1 year old suggests females may breed soon after losing a litter, as predicted by Seidensticker et al. (1973). While the average age of first breeding is similar to that observed in other cougar populations (Anderson 1983:31), 1 female bred when 17 months old. This female had remained and established in her dead moth- er's home range. Rapid establishment and early breeding by progeny of residents undoubtedly contributes to resiliency in cougar populations. Immigrants would not likely replace lost resi- dents as quickly or breed as soon as recruited

progeny (Laing and Lindzey 1993). Earlier, we hypothesized that the cougar pop-

ulation would increase as the mule deer popu- lation grew (Hemker et al. 1984) because cougar and deer populations were apparently below historic levels when we began our study. Indices of deer numbers and our general observations indicated that the deer population had grown over our study, although we could not document the actual magnitude of the increase. Number of resident adult cougars, however, generally remained stable through this period, and we demonstrated only a weak relationship between

cougar and deer numbers. While the observa- tions appear to support Seidensticker et al.'s (1973) thesis that the land tenure system of cou-

gars maintains the density of breeding adults below a level set by food supply alone, it is

possible the increase in deer numbers on our

study area was insufficient to provide an ade-

quate test of their hypothesis.

MANAGEMENT IMPLICATIONS Factors that can be important in determining

cougar density will likely change over the rel-

atively long period necessary to monitor con- current changes in cougar and prey populations, making it difficult to define the relationship be- tween cougars and their prey under natural con- ditions. Intuitively, one would not expect cougar population dynamics to be independent of those of their principal prey. The few studies that have examined this relationship (Hornocker 1970, Seidensticker et al. 1973, this study) may simply have been conducted when prey was abundant enough that other features of the en- vironment set allowable resident cougar densi- ties. Experimental manipulations of prey pop- ulations would enable examination of the relationship between cougar and prey at the

extremes of the prey abundance spectrum and reduce the potentially confounding effect of other variables if done over a short period.

LITERATURE CITED ACKERMAN, B. B. 1982. Cougar predation and eco-

logical energetics in south-central Utah. M.S. Thesis, Utah State Univ., Logan. 95pp.

ANDERSON, A. E. 1983. A critical review of liter- ature on puma (Felis concolor). Colorado Div. Wildl. Spec. Rep. 54, Denver. 99pp.

ASHMAN, D. L., G. C. CHRISTENSEN, M. C. HESS, G. K. TUSKAMOTO, AND M. S. WICKERSHAM. 1983. The mountain lion in Nevada. Nevada Dep. Wildl. Rep. 4-48-15, Reno. 75pp.

BARNHURST, D. 1986. Vulnerability of cougars to hunting. M.S. Thesis, Utah State Univ., Logan. 66pp.

CLARK, W., D. A. JESSUP, AND A. ADAMS. 1979. Animal restraint handbook. California Dep. Fish and Game, Sacramento. 113pp.

EATON, R. L., AND K. A. VELANDER. 1977. Repro- duction in the puma: biology, behavior and on- togeny. World's Cats 3:45-70.

GARCELON, D. K. 1977. An expandable drop-off transmitter collar for young mountain lions. Calif. Fish and Game 63:185-189.

HEMKER, T. P. 1982. Population characteristics and movement patterns of cougars in southern Utah. M.S. Thesis, Utah State Univ., Logan. 59pp.

1- , F. G. LINDZEY, AND B. B. ACKERMAN. 1984. Population characteristics and movement pat- terns of cougars in southern Utah. J. Wildl. Man- age. 33:457-464.

HOPKINS, R. A., M. J. KUTILEK, AND G. L. SHREVE. 1986. Density and home range characteristics of mountain lions in the Diablo Range of Cali- fornia. Pages 223-235 in S. D. Miller and D. D. Everett, eds. Cats of the world: biology, conser- vation and management. Natl. Wildl. Fed., Washington, D.C.

HORNOCKER, M. G. 1970. An analysis of mountain lion predation upon mule deer in the Idaho Prim- itive Area. Wildl. Monogr. 21. 39pp.

LAING, S. P., AND F. G. LINDZEY. 1991. Cougar habitat selection in south-central Utah. Pages 27- 37 in C. E. Braun, ed. Mountain lion-human interaction. Colorado Div. Wildl., Denver.

, AND- . 1993. Patterns of replacement of resident cougars in southern Utah. J. Mammal. 74:1056-1058.

LINDZEY, F. G., W. D. VAN SICKLE, S. P. LAING, AND C. S. MECHAM. 1992. Cougar population re- sponse to manipulation in southern Utah. Wildl. Soc. Bull. 20:224-227.

LOGAN, K. A. 1983. Mountain lion habitat and pop- ulation characteristics in the Big Horn Mountains of north-central Wyoming. M.S. Thesis, Univ. Wyoming, Laramie. 67pp.

NEFF, D. J. 1968. The pellet-group count technique for big game trend, census, and distribution: a review. J. Wildl. Manage. 32:597-614.

ROBINETTE, W. L., J. S. GASHWILER, AND O. W. MoRRIs. 1961. Notes on cougar productivity and life history. J. Mammal. 42:204-217.

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624 COUGAR POPULATION DYNAMICS o Lindzey et al. J. Wildl. Manage. 58(4):1994

SEIDENSTICKER, J. C., M. G. HORNOCKER, W. V. WILES, AND J. P. MESSICK. 1973. Mountain lion social organization in the Idaho Primitive Area. Wildl. Monogr. 35. 60pp.

SHAW, H. G. 1977. Impacts of mountain lions on mule deer and cattle. Pages 17-32 in R. L. Phil- lips and C. J. Jonkel, eds. Proc. 1975 predator symposium. Mont. For. Conserv. Exp. Stn., School For., Univ. Montana, Missoula.

TEW, R. K. 1972. Land systems inventory on the

Escalante Ranger District, Dixie National Forest. U.S. For. Serv. Tech. Rep., Cedar City, Ut. 95pp.

UTAH DIVISION OF WILDLIFE RESOURCES. 1990. Utah big game investigations and management recommendations, 1989-90. Utah Div. Wildl. Resour. Publ. 90-1, Salt Lake City. 116pp.

Received 7 August 1992. Accepted 29 March 1994. Associate Editor: Sauer.

IMPACT OF A SARCOPTIC MANGE EPIZOOTIC ON A COYOTE POPULATION

DANNY B. PENCE, Department of Pathology, Texas Tech University Health Sciences Center, Lubbock, TX 79430 LAMAR A. WINDBERG, USDA/APHIS, Denver Wildlife Research Center, Utah State University, Logan, UT 84322

Abstract: Although sarcoptic mange is a mite (Sarcoptes scabiei) infection that occurs as periodic epizootics in wild canids, the effect of this disease on populations has not been explained. We collected data from 1,489 coyotes (Canis latrans) during 1974-91 in southern Texas and examined the effect of a sarcoptic mange epizootic on the coyote population. Mange appeared in 1975, peaked during spring 1980 (69% of coyotes infected), and then decreased until absent among coyotes collected in 1991. The epizootic encompassed 60,000 km2 in southern Texas during 1982-89. Adult males were more (P < 0.001) frequently infected than other age-sex classes during the stationary phase of peak prevalence. Mange prevalence in juvenile males increased (P < 0.01) overwinter during the stationary and decline phases of the epizootic. There were more cases of severe mange among adult males (P < 0.01) during the stationary than the decline phase. Reduced ovulation (P = 0.04) and pregnancy rates (P = 0.03) were associated with greater mange severity in adult females. Usually, coyotes with severe mange had less (P < 0.05) internal fat. We suggest that this epizootic was initiated by the appearance of a virulent strain of S. scabiei in the host population, spread of the epizootic was enhanced by high host population densities but moderated by the social organization of coyotes, and decline of the epizootic resulted from selection for mange-resistant individuals in the host population. Understanding the effect of diseases on wildlife populations requires long-term analysis of host population dynamics, with attention to other relevant factors such as behavior.

J. WILDL. MANAGE. 58(4):624-633

Key words: Canis latrans, coyote, epizootic disease, population dynamics, Sarcoptes scabiei, sarcoptic mange, Texas.

Pence et al. (1983) documented the effects of a sarcoptic mange epizootic on a coyote popu- lation in southern Texas over 7 years (1975-81). Although the mortality rate among mange-in- fected individuals was greater than among un- infected coyotes during 1979-80, it was com- pensatory with overall mortality in the population (Pence et al. 1983).

The high-density coyote population (0.9-2.0 coyotes/km2 in spring) in southern Texas had a well-developed social organization (Andelt 1985, Windberg and Knowlton 1988) and experienced light exploitation by humans (Windberg et al.

1985). The diverse food base was consistently abundant (Brown 1977, Windberg and Mitchell 1990). In conjunction with other studies, we monitored the prevalence and severity of mange in this population during 1981-91. We present data for the duration of the epizootic to further assess its dynamics and effect on the coyote pop- ulation. Our objectives were to (1) describe sta- tionary through decline phases of the mange epizootic (1979-91), (2) compare the severity of mange infection across temporal (seasons) and host (age and sex) factors over the latter years of the epizootic, and (3) reassess the effect of

Pence et al. (1983) documented the effects of a sarcoptic mange epizootic on a coyote popu- lation in southern Texas over 7 years (1975-81). Although the mortality rate among mange-in- fected individuals was greater than among un- infected coyotes during 1979-80, it was com- pensatory with overall mortality in the population (Pence et al. 1983).

The high-density coyote population (0.9-2.0 coyotes/km2 in spring) in southern Texas had a well-developed social organization (Andelt 1985, Windberg and Knowlton 1988) and experienced light exploitation by humans (Windberg et al.

Received 7 August 1992. Accepted 29 March 1994. Associate Editor: Sauer.

624 COUGAR POPULATION DYNAMICS o Lindzey et al. J. Wildl. Manage. 58(4):1994

Escalante Ranger District, Dixie National Forest. U.S. For. Serv. Tech. Rep., Cedar City, Ut. 95pp.

UTAH DIVISION OF WILDLIFE RESOURCES. 1990. Utah big game investigations and management recommendations, 1989-90. Utah Div. Wildl. Resour. Publ. 90-1, Salt Lake City. 116pp.

1985). The diverse food base was consistently abundant (Brown 1977, Windberg and Mitchell 1990). In conjunction with other studies, we monitored the prevalence and severity of mange in this population during 1981-91. We present data for the duration of the epizootic to further assess its dynamics and effect on the coyote pop- ulation. Our objectives were to (1) describe sta- tionary through decline phases of the mange epizootic (1979-91), (2) compare the severity of mange infection across temporal (seasons) and host (age and sex) factors over the latter years of the epizootic, and (3) reassess the effect of

SEIDENSTICKER, J. C., M. G. HORNOCKER, W. V. WILES, AND J. P. MESSICK. 1973. Mountain lion social organization in the Idaho Primitive Area. Wildl. Monogr. 35. 60pp.

SHAW, H. G. 1977. Impacts of mountain lions on mule deer and cattle. Pages 17-32 in R. L. Phil- lips and C. J. Jonkel, eds. Proc. 1975 predator symposium. Mont. For. Conserv. Exp. Stn., School For., Univ. Montana, Missoula.

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IMPACT OF A SARCOPTIC MANGE EPIZOOTIC ON A COYOTE POPULATION

DANNY B. PENCE, Department of Pathology, Texas Tech University Health Sciences Center, Lubbock, TX 79430 LAMAR A. WINDBERG, USDA/APHIS, Denver Wildlife Research Center, Utah State University, Logan, UT 84322

Abstract: Although sarcoptic mange is a mite (Sarcoptes scabiei) infection that occurs as periodic epizootics in wild canids, the effect of this disease on populations has not been explained. We collected data from 1,489 coyotes (Canis latrans) during 1974-91 in southern Texas and examined the effect of a sarcoptic mange epizootic on the coyote population. Mange appeared in 1975, peaked during spring 1980 (69% of coyotes infected), and then decreased until absent among coyotes collected in 1991. The epizootic encompassed 60,000 km2 in southern Texas during 1982-89. Adult males were more (P < 0.001) frequently infected than other age-sex classes during the stationary phase of peak prevalence. Mange prevalence in juvenile males increased (P < 0.01) overwinter during the stationary and decline phases of the epizootic. There were more cases of severe mange among adult males (P < 0.01) during the stationary than the decline phase. Reduced ovulation (P = 0.04) and pregnancy rates (P = 0.03) were associated with greater mange severity in adult females. Usually, coyotes with severe mange had less (P < 0.05) internal fat. We suggest that this epizootic was initiated by the appearance of a virulent strain of S. scabiei in the host population, spread of the epizootic was enhanced by high host population densities but moderated by the social organization of coyotes, and decline of the epizootic resulted from selection for mange-resistant individuals in the host population. Understanding the effect of diseases on wildlife populations requires long-term analysis of host population dynamics, with attention to other relevant factors such as behavior.

J. WILDL. MANAGE. 58(4):624-633

Key words: Canis latrans, coyote, epizootic disease, population dynamics, Sarcoptes scabiei, sarcoptic mange, Texas.

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