Temporal Variation in Growth Rate and Age at Maturity of Male Painted Turtles, Chrysemys picta

Abstract

-Growth rates of juveniles and age at maturity of males were examined in a population of painted turtles, Chrysemys picta, inhabiting a marsh in southwestern Michigan (approximately 42024'N, 85024'W) to compare temporal variation in these two important life history traits within a decade. Elongation of the third right foreclaw was used as an indicator of incipient sexual maturity of males. Males in the late 1980s reached maturity at least a year earlier than did those in the early 1980s. Analysis of climatological data revealed that growing seasons in the late 1980s were typically warmer and longer than in the early years of the decade. The observed changes in juvenile growth rates and age at maturity of male C. picta are in accord with recent field and laboratory studies of emydid turtles. They also support predictions of life history theory, and may serve as working hypotheses that can be tested with data from other long-term projects. If substantiated, these patterns may indicate how some freshwater turtle populations in temperate latitudes might respond to predicted global warming trends.