Changes in Abundance of Gopher Tortoise Burrows at Cape Sable, Florida

Abstract

Abstract The southernmost population of Gopherus polyphemus (Gopher Tortoises) occurs at Cape Sable, FL. The burrows of this population were surveyed in 1979 using strip transects to estimate Gopher Tortoise burrow density. We present data from a 1990 strip-transect survey and a 2001 line-transect survey of burrows for comparison. We found a significantly lower density of active burrows and a significantly higher density of abandoned burrows in 2001 compared to 1979 and 1990, but the overall density of burrows did not differ significantly over time. The distribution of burrow widths in 2001 was not significantly different from the 1982 distribution, and the bimodal pattern suggests that reproduction has occurred at the site. The 76% decline of active burrows at the site suggests that Gopher Tortoises have been subject to mortality. Reduction of habitat quality and tropical storms are possible explanations for the apparent decline in the Gopher Tortoise population at Cape Sable, but more monitoring is requ...