Waif Gopher Tortoise Survival and Site Fidelity Following Translocation

Abstract

Gopher tortoises (Gopherus polyphemus) are among the most commonly translocated reptiles. Waif tortoises are animals frequently of unknown origin that have been displaced from the wild and often held in human possession for various reasons and durations. Although there are risks associated with any translocation, waif tortoises are generally excluded from translocation projects because of heightened concerns of introducing pathogens and uncertainty about the post-release survival of these individuals. If these risks could be managed, waif tortoises could have conservation value because they can provide the needed numbers to stabilize populations. In the early 1990s, the discovery of an isolated population of gopher tortoises (≤15 individuals) near Aiken, South Carolina, USA, prioritized establishment of the Aiken Gopher Tortoise Heritage Preserve (AGTHP). Because of the population's need for augmentation and the site's isolation from other tortoise populations, the AGTHP provided the opportunity to evaluate the post-release survival of translocated waif tortoises without compromising a viable population. Since 2006, >260 waif tortoises have been introduced to the preserve. Using a Cormack-Jolly-Seber modeling framework to analyze release records and capture histories from trapping efforts in 2017 and 2018, we estimated the long-term apparent survival and site fidelity of this population composed largely of waif tortoises. We estimated annual apparent survival probabilities to be high (≥0.90) for subadult, adult male, and adult female tortoises, and these rates were similar to those reported for wild-to-wild translocated gopher tortoises and those from unmanipulated populations. Of the tortoises recaptured within the boundaries of the preserve, 75% were located within 400 m of their release location. These results suggest that waif tortoises could be an important resource in reducing the extirpation risk of isolated populations.

Drivers of survival of translocated tortoises

“…Some gopher tortoises translocated to a protected area because of development died of stress‐related starvation within the first 2 years; models indicated that deaths occurred at sites with higher densities of translocated tortoises (Cozad et al 2020). Long‐term analyses of survival of translocated captive gopher and Hermann's tortoises in protected areas was high: ≥0.90 annually for subadult and adult gopher after approximately 12 years (McKee et al 2021) and 0.978 after 14 years and 0.972 after 29 years for Hermann's tortoises (Bertolero et al 2007, 2018). Predators negatively affected success of translocations of gopher and Herman's tortoises (Ashton and Burke 2007, Bertolero et al 2007, Pille et al 2018).…”

Warming conditions boost reproductive output for a northern gopher tortoise population

“…Translocations may be more successful (in terms of reproductive output of translocated females) if tortoises are moved northward to track their climatic niche as the climate continues to warm. Northward translocations are already occurring (Cozad 2018, McKee et al 2021, although not as an intentional response to a changing climate, but as a function of where land is available. To understand how movement of tortoises among climates within the species' range will impact the long-term persistence of translocated populations, it will be important to determine whether the effects that we have reported on here (warming conditions leading to increases in reproductive output) translate to other populations from warmer climates.…”

Movement Ecology of Gopher Tortoises in a Residential Neighborhood in Southwest Florida

“…The Gopher Tortoise has experienced significant population declines throughout its range (Hermann et al 2002) and is federally or state listed for protection within 6 states (Berry and Aresco 2014). As human-impacted areas have expanded and reduced Gopher Tortoise habitat, some populations remain in "island" pockets that can be small and/ or separated from other populations (McKee et al 2021). Understanding how threatened species, such as the Gopher Tortoise, respond in novel habitats, including urbanized environments, is important to determine their sustainability in different habitats and to reduce the likelihood of extirpation.…”