Female western pond turtles (Emys marmorata): their nesting season has begun at my field site in Lake County, Calfornia. The turtle in the first photo (#222, a recapture we first encountered in 2010) nested on June 6th – and yes, that photo was taken while she was in the process of laying her eggs. And the gorgeous girl in the other photos (#225, also first captured in 2010) nested on June 7th. The turtles seem to be coming out in greater numbers about a week earlier than they did last year.
The lab at my university has been studying this population of turtles for five years now (this is my third year on the project). We’re looking at nesting behavior, including the ways in which they use the habitat – distance from tree line, or distance from the pond, and whether or not the females return to the same spot year after year to nest. We’re also looking at temperature profiles inside of the nests, because these turtles have Temperature-dependent Sex Determination (TSD), which means that sex is determined by the temperature at which the eggs incubate, rather than genetically. (Higher temperatures produce females; lower temperatures produce males, in this particular species).