Multiscale Burrow Site Selection of Gopher Tortoises (Gopherus polyphemus) in Coastal Sand Dune Habitat

Abstract

Lau, A. and Dodd, C.K., Jr., 2015. Multiscale burrow site selection of gopher tortoises (Gopherus polyphemus) in coastal sand dune habitat. Journal of Coastal Research, 31(2), 305-314. Coconut Creek (Florida), ISSN 0749-0208.The gopher tortoise (Gopherus polyphemus) is a keystone species in upland sandhill ecosystems of the SE United States, and its habitat requirements have been well documented. Few studies have been conducted on populations that occur in coastal sand dunes. Because of close proximately to the ocean and highly fragmented linear habitat, coastal populations of gopher tortoises are affected by unique landscape factors that are not observed in upland contiguous populations. In this study, burrow site selection of gopher tortoises in a coastal sand dune site was quantitatively modeled. Significant biological, environmental, and anthropogenic factors that may influence burrow site selection at fine and coarse spatial scales were identified. Land cover type, distance to edge, soil resistance, percentage of herbaceous cover, slope angle, and number of tortoise burrows have significant influences on burrow site selection probability. Factors that influence burrow locations in coastal populations thus might differ in importance from those that influence burrow locations in more spatially contiguous upland populations. Our results indicate that coastal gopher tortoise populations require sitespecific management that focuses on the limited availability of optimal burrow construction sites.

Adapting coastal management to climate change: Mitigating our shrinking shorelines

“…Brazilian pepper is also unsuitable forage for tortoises, and is currently targeted for active herbicide‐spraying by the USFWS at KSC. Results from this study reinforce previous research linking open sandy areas and herbaceous cover to increasing densities of coastal gopher tortoises in Florida (Breininger et al , Lau and Dodd ). However, our results are based on only 2 years of surveys, representing a small fraction of the lifespan of a tortoise.…”

“…As we predicted, estimates of gopher tortoise density generated by our top model were significantly higher for the constructed dunes versus natural dues at MINWR, and the overall tortoise density for constructed dunes was similar to previously reported values for natural coastal tortoise populations elsewhere (0.64–3.05 burrows/ha, Lau and Dodd []; 0–30.7 individuals/ha, Breininger et al []). We found the first burrow on the 2014 dune approximately 3 months post‐construction, with a rapid increase in burrows prior to the first transect being completed in the area.…”

“…Our results agree with those of Breininger et al (), who reported tortoise density at KSC to be positively associated with an increase in areas that were disturbed and supported herbaceous vegetation. Lau and Dodd () also reported a significant, positive relationship between herbaceous cover and coastal tortoise burrow density.…”

“…Additionally, improper translocations contribute to population declines (Berry and Aresco ). Prior studies on coastal populations of gopher tortoises (Breininger et al , Lau and Dodd ) reported that density was positively associated with ruderal and open herbaceous cover as a source of food, whereas coverage by woody vegetation was negatively associated with density. By evaluating colonization rates and local population sizes on constructed dunes, we sought to determine if gopher tortoise density along constructed dunes was similar to surrounding natural dunes, and if constructed dunes would function for a managed retreat as sea‐levels rise.…”

Assessing Postfire Vegetative Changes and Implications for Management in a Northeast Florida Coastal Strand Ecosystem

“…In spite of its conservation ranking, there exists a paucity of information about managing the highly threatened coastal strand ecosystem (Simon 1986, Lau andDodd 2015). In addition to the many threats described previously, coastal natural communities worldwide share widely similar xeric vegetative structure and patterns of zonation (Doing 1985, Acosta et al 2000, Isermann 2011.…”