Decreased female survival may explain wild turkey decline

Abstract

Recent declines in wild turkey (Meleagris gallopavo) populations have prompted extensive research efforts and adjustments to state hunting regulations across the range of wild turkeys. However, research comparing historical and modern vital rates is needed to identify demographic factors that may explain declines. Based on matrix models, adult female survival has the greatest effect on the intrinsic rate of growth. Thus, we hypothesized that changes in annual female survival may explain contemporary declines in populations if that vital rate has decreased concomitant with population declines. We searched peer-reviewed literature, student theses and dissertations, and government reports for empirical estimates of annual female survival across the range of wild turkeys. Of the 51 resulting estimates of annual female survival across all subspecies, most were [≥]0.6 through 2012, but 8 out of 10 estimates post-2012 were lower, consistent with observed trends in population trajectories. We used matrix models to illustrate that the observed change in annual female survival estimates indeed predicts a declining population trajectory, even when other important vital rates are at the high end of the published range of process variation. If the published annual female survival estimates represent those experienced more broadly in populations, our meta-analysis and matrix models indicate that decreases in this vital rate help explain declines observed in populations in some regions. The causative factor(s) associated with the apparent declines are unknown, and little research has evaluated management strategies to increase annual female survival. Accordingly, we encourage wild turkey researchers to focus efforts on producing robust estimates of annual female survival, cause-specific mortality, and rigorous evaluation of management strategies to improve annual female survival.