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

Abstract

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 (Tbreed = 4.3 years, SD = 1.15, n = 9), an age not significantly different from that observed in the wild (Tbreed = 3.6 years, SD = 1.2, n = 16). Numbers of pups weaned per litter were similar in captivity (Npups = 3.0, SD = 1.4, n = 25) and in the wild (Npups = 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 (Pbreed = 0.09, n = 43) and older females were far more likely to breed (Pbreed = 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 (Tbetween = 1.4 years, SD = 0.7, n = 11) were significantly shorter than in the wild (Tbetween = 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.

Spatiotemporal variation in reproductive parameters of yellow-bellied marmots

“…Our long-term study of yellow-bellied marmots provided adequate data for a thorough examination of the spatiotemporal variation in Fig. 3a-e Variation from 1963to 2005 in probability of transition (mean ± SE) from a yearling (w 13 ), b subadult (w 23 ), and c adult (w 33 ) states to the reproductive adult state, as well as d litter size, and e realized population growth rate. Mean values (solid lines) and standard errors (shaded area) were estimated using model 2 (w 13 ), model 3 (w 23 ) and model 4 (w 33 ) in Table 2; model 9 (litter size) in Table 3 and model 2 (k) in Table 4 reproductive parameters.…”

“…The probability that an individual of reproductive age reproduces in a given breeding season is typically less than 1.0, and this probability can vary over space or time (e.g., Bryant 2005;Jenouvrier et al 2003;Watson and Moss 1970). A change in breeding probability can cause variation in population growth rate and thus population dynamics, even when average litter or clutch size remains relatively stable.…”

Patterns of within and between-colony microsatellite variation in the endangered Vancouver Island marmot (Marmota vancouverensis): implications for conservation

“…Vancouver Island marmots were live-trapped from 1993 through 2000 as part of a longer-term demographic study (Bryant 1998(Bryant , 2005. Trapping and handling methods followed Bryant (1996).…”

“…The program was later expanded, with marmots eventually breeding at Toronto, Calgary Zoo, Mountain View Farm near Vancouver, and a specially-designed facility on Vancouver Island that is situated in close proximity to natural marmot habitats (Bryant 2005). A total of 56 wildborn individuals were brought into captivity between 1997 and 2004 (Bryant 2007).…”

“…Our purpose was to establish whether Vancouver Island marmots were highly inbred compared to other marmot species, to identify patterns of genetic variation among colonies, and to determine whether the variation could be explained by standard isolation-by-distance models. All of these questions have direct relevance for future management of the captive-breeding program, particularly in terms of establishing breeding pairs that would retain maximum genetic variability from the wild genome (Bryant 2005). As such they are of critical importance towards eventual recovery of wild marmot populations.…”