Burrow Persistence and Spatial Distribution of Federally and State‐Protected Gopher Tortoise ( Gopherus polyphemus ) Populations in Southwest Alabama

The gopher tortoise ( Gopherus polyphemus ) is an ecosystem engineer and keystone species that has experienced population declines of roughly 80% over the past century due to human‐induced habitat loss. In the state of Alabama, the gopher tortoise was designated as a federally threatened species by the US Fish and Wildlife Service west of the Mobile–Tombigbee River (e.g., Mobile County) in 1987. East of the Mobile–Tombigbee River (e.g., Baldwin County), the gopher tortoise is protected only by state agencies. In this case study, we investigate the persistence of localized gopher tortoise populations in federally protected (Mobile) and federally unprotected (Baldwin) counties across a 28‐year period from initial surveys in 1991–1992 to our recent survey in 2018–2020. In addition, we use GIS modeling and 597 burrow coordinates to develop a novel approach to mapping the potential suitable habitat availability in Mobile and Baldwin counties. Our survey results indicate that gopher tortoise populations have declined in both counties since 1991–92, with populations persisting at ~59% of sites in Mobile County and ~31% of sites in Baldwin County, along with a 9.3% decline in burrow abundance in Mobile County and a 20.8% decline in burrow abundance in Baldwin County. Despite an overall decrease in the total number of burrows since 1991–92, there has been a significant increase in the proportion of active status burrows in both counties (Mobile County, 21% increase, and Baldwin County, 25% increase), most likely the result of remnant populations concentrating into suitable habitat. Our GIS model revealed there is a large amount of suitable habitat (232,657 ha) in southwest Alabama to support growing gopher tortoise populations. However, the overall decline in active site persistence and burrow density is likely indicative of the pressure on tortoise populations from increasing human populations.