Abstract
In reptiles, reproductive maturity is often determined by size rather
than age. Consequently, growth early in life may influence population
dynamics through effects on generation time and survival to
reproduction. Because reproductive phenology and pre- and post-natal
growth are temperature-dependent, environmental conditions may induce
multi-species cohort effects on body size in sympatric reptiles. I
present evidence of this using ten years of neonatal size data for three
sympatric viviparous snakes, Dekay’s Brownsnakes (Storeria dekayi),
Red-bellied Snakes (S. occipitomaculata) and Common Gartersnakes
(Thamnophis sirtalis). End-of-season neonatal size varied in parallel
across species such that snout-vent length was 36-61% greater and mass
was 65-223% greater in years when gestating females could achieve
higher April-May (vs. June-July or August-September) operative
temperatures. Thus, temperature had a larger impact during follicular
enlargement and ovulation than during gestation or post-natal growth.
Multi-species cohort effects like these may affect population dynamics
and increase with climate change.