| Popis: |
Gopher tortoises (Gopherus polyphemus) occur in open-canopy pine habitat on well-drained soils in the southeastern United States, where they construct burrows that offer protection from thermal extremes, fire, and predators. Gopher tortoise populations have declined over the past 50 y, primarily as a result of habitat loss and degradation. Southeastern pine forests require active management with prescribed fire, mechanical thinning, or removal of hardwoods to maintain suitable habitat for gopher tortoises. In addition, many pine forests in the Southeast that support gopher tortoise populations are managed for multiple uses including intensive silviculture. Heavy equipment associated with these activities used in proximity to gopher tortoise burrows can cause them to collapse, potentially causing harm to tortoises or other imperiled organisms that use their burrows. Hence, there is a need for practical guidelines for use of heavy equipment for timber harvest, management, and other activities around gopher tortoise burrows to minimize risk to tortoises. We conducted a field study to determine the distance at which heavy equipment caused gopher tortoise burrows to collapse using a feller buncher, rubber-tire front-end loader, and an agricultural tractor with a tree-mower attachment in sandy clay loam (15 burrows) and undifferentiated deep sand (15 burrows) soils at a site in southwestern Georgia. All burrows were confirmed to be unoccupied by tortoises or other vertebrate commensal species using a camera scope before collapse. The greatest mean distance to collapse across all vehicles tested in sandy clay loam and undifferentiated deep sand was 2.19 ± 0.56 m and the maximum distance to collapse was 3 m. Given the variation in collapse distance, we recommend a buffer that extends 4 m in radius from the entrance of the gopher tortoise burrow to minimize risk of collapse from heavy equipment. |
