Quantifying the effects of nest management and environmental change on demography of an endangered sea turtle

Abstract

Understanding the demographic drivers of reintroduced and translocated populations is critical for species establishment and persistence. Given the large number of resources required to conduct ongoing reintroduction and reinforcement programs, additional information on population responses to management practices could help identify key actions that best benefit a species while ensuring economic feasibility. An integrated population model (IPM) can be used to assess and forecast the demographic consequences of different management practices and the interrelationship between management effects, population dynamics, and environmental change. We used an IPM to inform the potential impacts of nest management practices and global climate change on the vital rates of the Texas nesting colony of the endangered Kemp's ridley sea turtle. We used the IPM to estimate population parameters including adult survival, population growth rate, and abundance of nesting females in Texas. Additionally, given potential future scenarios for management and environmental change, we used the IPM to forecast population change and estimate the probability of persistence of the Texas population under future environmental and management scenarios. Future scenarios for nest management that had some level of management (i.e., not all nests were left in situ) resulted in population growth rates that were likely stable or increasing. Scenarios in which all nests were left in situ resulted in stable or decreasing population growth rates as well as a probability of extirpation from Texas >1 (p(N = 0 in 2100) = 0.25–0.72). Despite uncertainty in forecasted abundance and population growth rates under all scenarios, our model still predicted stable or increasing population growth rates with a continuation of current nest management practices. In contrast, we found that reduced population growth was expected with reduced nest management effort, and population decline and extirpation was expected with no management. Our IPM framework provides an example of how future management scenarios can be evaluated critically to determine population changes through time under future environmental uncertainty.