Burrow Characteristics and Habitat Associations of Gopher Tortoises in Urban Pine Rockland Reserves (Miami, Florida, USA)

Abstract

The Gopher Tortoise is a keystone species and a species of conservation concern in the southeastern United States, but the biology of tortoises at the extreme southeastern limit of the range is poorly understood. We examined physical characteristics and habitat associations of Gopher Tortoise burrows in pine rockland natural preserves in the highly urbanized Miami-Dade County (Florida, USA). We measured width, depth, and orientation of burrows at two sites. We compared a suite of 11 habitat features (e.g., canopy cover, understory density, ground cover, soil depth, and soil compaction) at random points and at Gopher Tortoise burrows in each of the two sites. Burrow widths were similar between sites and included burrows of both adults and juveniles—evidence that both populations are reproducing. Burrows were very short (most <2 m) compared to burrow lengths reported from other sites (>4 m), likely because soil depth is very shallow in extreme south Florida. We used multidimensional scaling and analysis of similarity to detect differences in habitat variables among sites, among point types (random points and burrows), and between active and inactive burrows. Low leaf litter cover, high grass cover, low canopy cover, and deep soil were among the major variables associated with all burrows and active burrows. The habitat associations of the burrows were similar to studies from other areas, yet the short burrows and association with the deepest available soils appear to be a strong response to the unique geology of pine rockland habitats. We discuss vegetative associations of Gopher Tortoises in the context of management in urban natural areas and implications for protection of Gopher Tortoises at the southern limit of their geographic range.