Cougar Population Dynamics and Viability in the Pacific Northwest

Abstract

Increasing reports of human/cougar conflicts may suggest that cougars are increasing in the Pacific Northwest. We determined minimum relative densities and average fecundity, survival, and growth rate of an apparently increasing cougar population in northeastern Washington, USA; northern Idaho, USA; and southern British Columbia, Canada, from 1998 to 2003. Minimum relative densities declined from 1.47 cougars/100 km2to 0.85 cougars/100 km2. We estimated average litter size at 2.53 kittens, interbirth interval at 18 months, proportion of reproductively successful females at 75%, and age at first parturition at 18 months for a maternity rate of 1.27 kittens/adult female/yr. Average survival rate for all radiocollared cougars was 59%: 77% for adult females, 33% for adult males, 34% for yearlings, and 57% for kittens. Hunting accounted for 92% of mortalities of radiocollared cougars. The annual stochastic growth rate of this population was Λ = 0.80 (95% CI = 0.11). Contrary to accepted belief, our findings suggest that cougars in the Pacific Northwest are currently declining. Increased conflicts between cougars and humans in this area could be the result of the 1) very young age structure of the population caused by heavy hunting, 2) increased human intrusion into cougar habitat, 3) low level of social acceptance of cougars in the area, or 4) habituation of cougars to humans. To help preserve this population, we recommend reduced levels of exploitation, particularly for adult females, continuous monitoring, and collaborative efforts of managers from adjacent states and provinces.

Does genetic introgression improve female reproductive performance? A test on the endangered Florida panther

“…Our results provide strong evidence of reproductive senescence (manifested as a lower probability of reproduction) in older Florida panthers, but suggest that age-specific differences in reproduction prior to senescence are minor. The overall average litter size was 2.60 ± 0.09; this estimate, although slightly higher than previous estimates for Florida panthers (Lotz et al 2005: 2.4;Maehr and Caddick 1995: 2.25), is within the range of litter size estimates reported for western populations of pumas (1.7-3.0; Cooley et al 2009;Lambert et al 2006;Laundré et al 2007;Logan and Sweanor 2001;Robinson et al 2008;Stoner et al 2006). Sub-adult females produced somewhat larger litters.…”

Does hunting regulate cougar populations? A test of the compensatory mortality hypothesis

“…To determine intervals when survival probabilities were constant, we analyzed the statistical distribution of deaths over a 365-day period (Lambert et al 2006). This yielded two mortality seasons: a high-mortality season (LH: 1 August to 31 December, HH: 1 October to 31 January) and a low-mortality season (LH: 1 January to 31 July, HH: 2 February to September 31).…”

Overestimates of maternity and population growth rates in multi-annual breeders

“…Some researchers (Lambert et al 2006) modified the standard mean litter size/mean birth interval ratio by estimating percentage of unproductive females (those with litters of zero and indeterminate birth intervals) and multiplying the reciprocal of this percentage by the standard ratio estimate. Others (Chapron et al 2003;McLoughlin et al 2003b;Wielgus et al 2001) estimated Mx using a probabilistic approach-which incorporates the probabilities of producing from 0 to N offspring on an annual basis.…”