Bruce B. Ackerman

Cougar Population Dynamics in Southern Utah

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 cougars 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

Survival Rates of Mountain Lions in Southern Utah

We monitored survival of resident mountain lions (Felis concolor) during a radio-telemetry study between 1980 and 1986 in southern Utah. Yearly survival of resident adults ranged from 52 to 100% (9 = 74%). Causes of death included intraspecific killing, injury related to prey capture, trapping, and starvation. Deaths of dispersing offspring were human-related. J. WILDL. MANAGE. 52(4):664-667 Mountain lions were first protected as game animals in the 1960s (Nowak 1976). Since that time, most states and provinces with viable mountain lion populations have assumed authority for their management. Management efforts have been hindered by a lack of data on the dynamics of mountain lion populations. Annual mortality rates were estimated by Robinette et al. (1977:123) at 32% based on the age distribution of harvested mountain lions. Ashman et al. (1983) reported similar mortality rates from the percent of marked animals harvested. Tanner (1975) reported an annual survival rate for mountain lions 1-13 years old of 88%, which he calculated from the literature (principally Hornocker 1970), and a highest survival rate of 95%, which he felt was possible in an optimum environment. Sport hunting is the major humanrelated cause of death for mountain lions. Other causes of death include predator control programs, injuries suffered during attempts to capture prey (Gashwiler and Robinette 1957, Hornocker 1970), intraspecific killing (Robinette et al. 1961, Hemker et al. 1984) and starvation (H. G. Shaw, Ariz. Game and Fish Dep., pers. commun.). Survival rates are commonly used in management programs but are difficult to estimate for long-lived, secretive mammals occurring at low densities. Inadequate or biased samples and failure to meet necessary assumptions often preclude use of techniques traditionally used to estimate survival rate, such as life table analysis (Caughley 1977:85-106). We analyzed longterm telemetry records and estimated survival rates for resident mountain lions using 2 techniques: MICROMORT (Heisey and Fuller 1985) and product-limit (Kurzejeski et al. 1987). We appreciate suggestions on analyses provided by G. C. White and D. R. Anderson and the field assistance of A. J. Button, W. W. Button, J. Roberson, T. D. Becker, F. G. Van Dyke, V. Judkins, C. H. Greenwood, and C. S. Mecham. Funding for this project was provided by the Utah Division of Wildlife Resources. The project was conducted under auspices of the Utah and Wyoming Cooperative Fishery and Wildlife research units.