Reproductive rates of wild and captive Vancouver Island marmots (Marmota vancouverensis)

I evaluated reproductive rates of the critically endangered Vancouver Island marmot (Marmota vancouverensis Swarth, 1911) using data from captive and wild populations over the 1980-2004 period. Results were similar to those reported for other alpine-dwelling marmots, including the closely related Marmota caligata (Eschscholtz, 1829) and Marmota olympus (Merriam, 1898). Most females in captivity first bred at age 3 or 4 (T-breed = 4.3 years, SD = 1.15, n = 9), an age not significantly different from that observed in the wild (T-breed = 3.6 years, SD = 1.2, n = 16). Numbers of pups weaned per litter were similar in captivity (N-pups = 3.0, SD = 1.4, n = 25) and in the wild (N-pups = 3.4, SD = 1.1, n = 58). Females were capable of weaning pups in consecutive years (46.4%, n = 13) but often skipped 1 year (39.3%, n = 11) or 2 years (14.3%, n = 4) between litters. Two-year-old females weaned pups infrequently (P-breed = 0.09, n = 43) and older females were far more likely to breed (P-breed = 0.40, n = 200); in neither case were significant captive-wild differences found. The oldest breeding female was 10 years old, but sample sizes for marmots older than 8 years were small and maximum breeding age may be underestimated. Between-litter intervals in captivity (T-between = 1.4 years, SD = 0.7, n = 11) were significantly shorter than in the wild (T-between = 1.9 years, SD = 0.7, n = 17). Sex ratios of weaned pups did not differ from 1:1 in the wild (female/male = 1.04) but were significantly skewed towards males in captivity (female/male = 0.56). I conclude that reproductive performance in Vancouver Island marmots is limited both by body condition and social constraints.