Abstract Townsend's big‐eared bat ( Corynorhinus townsendii townsendii ) is a species of conservation concern in California, USA, due to human disturbance at roosts, destruction of roosting structures (e.g., mine closures), and vulnerability to habitat loss from climate change. Extreme weather events such as drought and high temperatures can reduce bat survival; however, little is known about climate‐related survival in this species. We estimated age‐specific yearly survival of female Townsend's big‐eared bats ( n = 1,726) from 18 maternity colonies over 9 years (2013–2022) in Inyo and Mono counties, California. We used a Cormack‐Jolly Seber model to estimate yearly survival as a function of age and drought severity between sampling occasions. To account for variation in detection methods, we also compared recapture probabilities between colonies monitored with hand‐netting alone and those with both hand‐netting and passive antenna arrays. We found that juvenile survival (0.20–0.44) was lower than adult survival (0.72–0.89), both juvenile and adult survival were negatively affected by drought, and detection probability was lower for bats recaptured solely with hand‐nets compared to bats detected via hand‐netting and pass‐through antenna arrays. Given that drought frequency and severity are projected to increase in California, Townsend's big‐eared bats will likely face heightened population declines. Our findings provide benchmarks for long‐term monitoring and assessing management effectiveness.
Hamilton et al. (2026) studied this question.