Life history constraints contribute to the vulnerability of a declining North American rattlesnake

Abstract

Delayed maturation and age-biased dispersal work in concert under past selection to maximize individual fitness and contribute to population viability; however, these life history attributes can become dysfunctional in a dynamic, anthropogenic landscape when important population demographics cannot redistribute in response to novel landscape change. We used long-term monitoring data to estimate age at maturity, potential longevity, survival, and fidelity for the declining eastern diamondback rattlesnake (EDB), Crotalus adamanteus. We used radio telemetry data and known-fate models to examine adult survival, and we combined mark-recapture and radio telemetry data to examine survival and fidelity using a combined recapture/recovery model. Monthly adult survival was higher during the active season (April–November; 99.5%) as compared to the inactive season (December–March; 96.3%), despite a higher probability of detecting human-caused mortalities during the active season. Rattlesnakes matured in 7.1years and potential longevity exceeded 20years. Fidelity estimates indicated mature EDBs had a low probability of dispersing from the study area, while younger, sexually immature individuals were more likely to emigrate. The combination of a slow life history and an ontogenetic shift in emigration suggests EDB life history limits the species’ ability to respond to landscape change, shedding further light on EDB imperilment. Management efforts will benefit from activities that maintain high adult survival. Furthermore, EDB fidelity should be considered in conservation plans, particularly in light of the species’ longevity, as these characteristics suggest that mature EDBs may not readily redistribute at the landscape scale in response to habitat degradation.