Proceedings of the Ninth Mountain Lion Workshop - Carnivore ...

Variation in the Reproductive Success of Female Cougars by Individual
Traits, Density, and Seasonal Weather.
Diana Ghikas, Canadian Wildlife Service, 300-2365 Albert Street, Regina, SK S4P 4K1,
Canada, Diana.Ghikas@ec.gc.ca
Martin Jalkotzy, Golder Associates, 1000-940 6th Avenue S.W., Calgary, AB T2P 3P1,
Canada, Martin_Jalkotzy@Golder.com
P. Ian Ross (Deceased)
ABSTRACT The vital rates (fecundity, survivorship) and migration rates of an animal
population determine its size and composition, and represent the combined life-history
performances of its constituents. Understanding how individual traits, population
characteristics, and extrinsic factors influence fecundity and survivorship is fundamental
to explaining the dynamics of a population. It can also reveal valuable insights about the
species’ life-history strategies. In addition, being able to predict changes in vital rates,
based on known associations with key explanatory variables, is important when
managing for a stable population.
To examine how the short-term reproductive success of adult female cougars varied with
an individual’s identity (i.e., age, size) and behavior (i.e., habitat use), conspecific
density, and weather, we analyzed long-term data of a hunted population of cougars in
SW Alberta studied by Jalkotzy and Ross during 1981-1994. We developed generalizedlinear
models to identify different influences on female reproductive output. Habitat use
was measured in a novel way, which accounted for extreme behavior, and out-performed
measuring the average habitat used.
Productive females were older and frequented habitats with 49% open-canopy cover) within 1.0 km 2 of a female’s location. Productivity varied
negatively with the density of independent cougars. Litter sizes were large when mothers
occupied mid-elevation habitats (summer: 1437-1745 m, winter: 1445-1678 m). Femalebiased
litters were reared when cougar density was low or when mothers experienced
harsh conditions: cold snowy winters and springs or poor-quality habitat. Plausible
explanations for sex-biased litters are presented.
Future challenges: Further studies are needed to investigate the mechanism by which a
mother rears a sex-biased litter; links between reproductive output, adult female
physiology, and habitat and weather conditions; and, density-dependent effects on
offspring sex ratios.
Proceedings of the Ninth Mountain Lion Workshop
256