Exploring Demographic Patterns in Yellow Mud Turtles: Trade-Offs Between Survival and Reproduction

Understanding demography is integral to understanding the ecology of any population. Given global concerns over declining turtle populations, having a better understanding of demography could have significant implications for the management and conservation of at-risk populations. Although demographic research has been increasing amongst turtles, we still lack an understanding of variation in demographic parameters amongst most turtle species. Without such an understanding, it becomes difficult to evaluate if a management strategy developed for one population or species could or should be applied to other populations or species. I explored patterns in survival and reproduction for yellow mud turtles (Kinosternon flavescens) by examining 6 populations in Texas from 2007-2018. I used age-structured regression from 3,132 captures of 1,973 individuals across the sites to produce survival estimates for each population and used x-rays to determine average clutch size and estimated both egg volume and clutch volume for each site. Annual survival varied from 62.2% to 87.6% across the 6 populations. Across 5 sites, clutch size ranged from 3.4 to 5.0, egg volume ranged from 3716 mm3 to 4388 mm3, and clutch volume ranged from 13991 mm3 to 17667 mm3. Variation in survival and reproduction did not appear to be related to a clinal gradient across the populations I examined. I detected no significant relationships between survival and reproduction within my populations. For both variables, within-site differences in habitat might be more significant drivers of demography than among-site differences, and the observed variation suggests this species has adopted a bet-hedging strategy rather than a more traditional K-selected strategy. Continued data collection in these and other populations should help clarify these relationships. With the anticipated effects of climate change in the southwestern United States, continuation of this study could provide an interesting opportunity to explore adaptive shifts in demography in response to increased climate variability.