Population models reveal the importance of early life‐stages for population stability of an imperiled turtle species

Abstract

AbstractDemographic models are useful for projecting population trends, identifying life stages, most important to population dynamics, and investigating the demographic effects of potential management scenarios. We incorporated site‐specific population parameters into stage‐based matrix models to estimate population growth and to assess potential management scenarios for five intensively sampled (>15 years) populations of federally threatened bog turtles (Glyptemys muhlenbergii) in North Carolina, USA. Only two of the five populations modeled were stable or growing under estimated vital rates. Long‐term sampling of bog turtle populations in NC suggests the declining populations in this study share several demographic characteristics with other populations in the region. Elasticity analysis revealed small changes in adult survival rates have the largest effect on population growth rate. These models also highlight that increased survival of egg and juvenile stages can sometimes buffer higher adult mortality and emigration, and reduced survival at multiple life stages can induce population‐level decline. Our results indicate that management scenarios targeting increased recruitment (especially a head‐start scenario) provide increased population growth among all populations, and allowed two of three declining populations to reach stability under current estimated vital rates. Population growth rates will be higher when population augmentation coincides with habitat restoration efforts that increase survival and site fidelity at all life stages. These models emphasize the importance of considering site‐specific dynamics when evaluating conservation interventions for an imperiled long‐lived species.