Loss of largest and oldest individuals of the Montpellier snake correlates with recent warming in the southeastern Iberian Peninsula

Climate but Not Land Use Influences Body Size of Fowler's Toad (Anaxyrus fowleri)

Anthropogenic changes to the environment have been associated with changes in body size of multiple organisms. However, although climate and land use influences on body size have been examined separately, the simultaneous effects and potential interactions of these two factors on body size have rarely been studied. We examined the size and mass of a common North American toad (Fowler's toad, Anaxyrus fowleri) using museum specimens from 1931 to 1998 to quantify the potential interactive effects of climate change (temperature and precipitation) and land use change (forested area) on body size. We found that snout-vent length (SVL) and mass declined over time, and that size was negatively related to both temperature and precipitation (smaller size at higher values of temperature and precipitation). We did not find evidence of an effect of forest cover on size or mass. Our results suggest that Fowler's toad body size is affected by climate but not land use, and we encourage further examination of additional species and land cover variables (such as urbanization) to determine whether our results are representative of ectotherms more broadly. This work highlights the strength of climate in determining anuran body size and contrasts with existing studies showing interactive effects of climate and land use on animal body size.

Decline in body size and female fraction in the grass snake (Natrix natrix, Linnaeus 1758) population after 40 years (Southern Poland)

Depletion of free-living populations is often associated with changes in fitness-related traits, e.g., body size. Ongoing decrease in body size has been reported in most vertebrates, but reptiles remain understudied. Moreover, sexual size dimorphism, commonly observed in reptiles, indicates that environmental pressures on body size may appear sex-specific. This can also result in shifts in sex ratio, an aspect even less studied. We investigated body size and sex ratio in population of grass snake (Natrix natrix) surveyed over 40 years ago in comparison with the current state. We found that both sexes express similar magnitude in body size decline. The current sex ratio does not deviate from 1:1, while in the past, females outnumbered males. The observed changes are likely an outcome of several non-mutually exclusive factors. In the studied area, an increase in road traffic and human presence and a drop in prey availability have been documented. Both factors may exert higher pressure on larger individuals, particularly females, due to their high costs of reproduction. It is recorded here that increase in ambient temperatures and summer duration may additionally enhance the mortality risk and resource requirements. Shifts in body size and sex ratio can catalyze further declines in abundance and reproductive potential of the population.