Proceedings of the Seventh Mountain Lion Workshop

MONITORING CHANGES IN COUGAR SEX/AGE STRUCTURE WITH CHANGES IN
ABUNDANCE AS AN INDEX TO POPULATION TREND
CHUCK R. ANDERSON, JR., Wyoming Cooperative Fish and Wildlife Research Unit, Box
3166, University Station, Laramie, WY 82071, USA, email: cander@uwyo.edu
FRED G. LINDZEY, Wyoming Cooperative Fish and Wildlife Research Unit, Box 3166,
University Station, Laramie, WY 82071 USA, email: flindzey@uwyo.edu
Abstract: Cougar (Puma concolor) management has traditionally been plagued by the inability to
identify population trends for adequate assessment of management strategies. Monitoring
changes in harvest sex-age structure as an index to population trends appears useful in tracking
black bear populations and may be applicable to cougar management, especially given their strict
social structure and territorial behavior. We documented changes in cougar harvest structure
(sex-age) through experimental population reduction and recovery to better understand the
relationship between sex-age composition and population trend in exploited populations. The
cougar population in the Snowy Range, southeast Wyoming, declined from 58 (90% CI = 36 to
81) in the fall of 1998 to 20 (90% CI = 14 to 26) independent cougars (>1 year old) by the spring
of 2000 following 2 years of increased exploitation (mean exploitation rate = 43%) and increased
to 46 (90% CI = 33 to 60) by the spring of 2003 following 3 years of reduced harvest levels
(mean exploitation rate = 18%). Pre-treatment harvest composition was 63% subadults (1.0-2.5
years old), 24% adult males, and 14% adult females (2 seasons; n = 22). A reduction in subadult
harvest, an initial increase followed by a reduction in adult male harvest, and a steady increase in
adult female harvest was consistent with hypothesized harvest vulnerability for a declining
population. Harvest composition was similar at high and low densities with light harvest, but the
proportion of male subadults increased at low density as adult males removed during the
treatment period (high harvest) were replaced. Examining cougar sex ratios (m:f) alone appears
to be of limited utility for identifying population change. Including age class, however, provides
a useful metric in monitoring cougar population trend. We feel this approach could be applied to
adaptively manage cougar populations where adequate sex and age data are collected from
harvested animals.
PROCEEDINGS OF THE SEVENTH MOUNTAIN LION WORKSHOP
137