Post‐release survival of captive‐reared Allegheny woodrats

Abstract

Captive breeding to augment wild animal populations is an important tool in the recovery of imperiled species, but low post-release survival and substantial program expenses require methodologies that maximize utility. We evaluated post-release survival of captive-reared Allegheny woodrats (Neotoma magister) introduced into a declining metapopulation in southern Indiana. We hardreleased 16 captive-reared woodrats in 2011 and soft-released 14 woodrats in 2012, while monitoring parallel samples of 16 and 17 wild-born individuals in each year, respectively. We obtained Kaplan-Meier estimates of survivorship for both groups and used Cox proportional hazards regression to estimate the association between survival and rearing environment (wild or captive), release strategy, sex, body condition and age at release. We quantified movement patterns and related the results of survival models to behavioral tendencies. Survivorship of wild-born individuals was consistently higher than captive-reared individuals. Patterns of survival were best explained by rearing environment and its interaction with time, although disparities in survival between wild-born and captive-reared animals decreased over time. Higher mortality among captive-reared individuals may have been due to more exploratory behavior, as captive-reared woodrats used more dens and traveled farther among successive relocations than wild-born conspecifics. Soft-released individuals had higher initial survival rates and tended to choose dens similar to those of wild individuals, providing evidence that this strategy eased the transition to a wild environment. We recommend future programs use soft-release techniques but also explore other pre-release preparatory strategies such as anti-predator conditioning and environmental enrichment to increase survival.

Comparing post-release survival and habitat use by captive-bred Cabot’s Tragopan (Tragopan caboti) in an experimental test of soft-release reintroduction strategies

“…Improvements of habitat selection behavior of captive-bred animals by acclimation training have also been documented by other captive-release studies (e.g. Bright and Morris 1994;Islam et al 2013;Blythe et al 2015).…”

Bayesian model-based age classification using small mammal body mass and capture dates

“…In addition to annual monitoring, study areas were part of ongoing woodrat recovery and research efforts associated with reinforcement of extant populations through translocation and monitoring of survival via radiotelemetry (Smyser et al 2013;Blythe et al 2015). Prior to the release of translocated woodrats, we conducted limited trapping to ensure that woodrats were released into vacant den sites, applying the same methods as described above at localized scales.…”

Efficacy of acclimating and releasing captive-reared and wild-translocated Northern bobwhites

“…37 A more precise term might be acclimation, referring to holding individuals to be released in an on-site enclosure for ⩾24 h before liberation into the wild. 38 On-site acclimation is hypothesized to increase site fidelity and post-release survival in multiple taxa, 37,[39][40][41][42] and may also decrease dispersal distance. 40,43,44 Decreased dispersal distance increases the probability of successful restoration attempts in some galliformes.…”