Seasonal variation in body mass and composition of eastern coyotes

Abstract

Fat and protein reserves were estimated from body mass and the kidney and femur fat index for 135 coyotes (Canis latrans) of different ages and both sexes. These coyotes were collected in southeastern Quebec during five trapping periods between summer 1990 and autumn 1991. Coyotes were 27–28% heavier during autumn–winter than during summer: 16.0 versus 12.5 kg for males and 14.0 versus 11.0 kg for females. This mass gain consisted of 0.6–0.7 kg of protein and 1.5–2.0 kg of fat (water accounted for the balance). The mean fat percentage varied widely among individuals but did not differ according to sex or age. It varied according to trapping period and almost doubled from summer to autumn (10 versus 18%), did not change significantly from late October to late March, but then decreased from winter to summer. It appears that fat deposits accumulated by coyotes during autumn were not used progressively during the winter. However, they allowed the coyotes to survive during brief periods of food shortage. Furthermore, spring and summer seemed to be periods of relative food scarcity for coyotes, because they lost 16–17% of their protein mass from late winter to summer. Only 41% of the 39 females old enough to reproduce ovulated, but no relationship was apparent between this low fertility rate and the body composition of the females.