Growth rate, reproductive output, and temperate selection of snapping turtles in habitats of different productivities

We compared temperature selection, growth and reproductive output between two populations, and movement and home range size among three populations of the common snapping turtle (Chelydra serpentina serpentina) occupying habitats with different productivities in Ontario, Canada. We examined the hypothesis that primary productivity constrains growth, reproductive effort, and thermal and home range behavior. We predicted that individuals in a habitat with high productivity would grow faster, produce larger clutches of eggs, select warmer temperatures, and maintain smaller home ranges than individuals in a less productive habitat. As expected, turtles in the more productive habitat grew more rapidly and had a higher reproductive output than those in the less productive habitat. Turtles maintained higher body temperatures at the more productive site, but this may have been because ambient temperatures were higher at the productive site rather than because turtles were selecting higher temperatures. Size of home range and distances moved did not differ among study populations, which suggests that productivity was not a good proximate measure of home range behavior. Differences among sites in ambient temperature, type and distribution of prey, and turtle density made it difficult to separate the effect of each factor on growth and reproduction. Future research should measure variation among individuals in energy flow, particularly to improve our understanding of variation in home range behavior.