Meeting Abstract
Cessation of breeding is characteristic of small mammals inhabiting areas that are seasonally cold or seasonally hot and arid. The reasons for cessation include lack of food or water to sustain reproduction or the competing costs of thermoregulation and reproduction. The impact of seasonality on breeding could affect several life history characteristics including adult body mass, growth rate, age at first reproduction, juvenile survivorship and rate of development. In this study, I compared the relationship between seasonality on rate of growth to weaning mass, mass at first reproduction and adult mass to determine if growth rate increases as the length of the favorable season for reproduction decreases. In a sample of non-hibernating rodents, larger species were significantly more likely to be classified as year-round breeders than smaller ones were. When the effect of adult body mass was held constant, the rate of attaining adult body mass was inversely related to the length of the breeding season. However, juvenile growth from birth to weaning and rate of attaining age at first reproduction were not significantly related to season length. Additionally, it appears that rapid growth in shorter habitats occurs concurrently with a decrease in neonatal development and an increase in litter size. Further work is needed to identify whether size-based overwinter adult mortality is the primary selection pressure selecting for faster growth in more seasonal habitats.
