Reproductive phenology and seasonal mass dynamics of black-tailed prairie dogs (Cynomys ludovicianus) at their northern range limit

Abstract

Intraspecific variation is common and can be substantial in species occupying large geographic ranges. For example, populations at a poleward range limit can be exposed to more severe and variable weather, resulting in more punctuated growing seasons and, consequently, large fluctuations in body mass and additional constraints on reproductive phenology. We monitored variation in these traits in a hibernating population of black-tailed prairie dogs (Cynomys ludovicianus (Ord, 1815)) at their northern range limit across four growing seasons. Overall, individual body mass was highly dynamic both within and across growing seasons, and was correlated with sex, the presence of drought, and reproductive effort. This population experienced between-year variation in the timing of reproduction that was associated with weather variation. The influence of weather was particularly evident in 1 year during which a summer–autumn drought was followed by a severe and prolonged winter. This combination led to high overwinter mortality, substantially delayed emergences from hibernation, lower body masses at emergence from hibernation, and complete reproductive failure the following spring. Our results help to emphasize the influence of environmental conditions on levels of phenotypic variation at a species’ northern range limit, which may ultimately contribute to population viability and success.