GOPHER TORTOISE RESEARCH
Master's Research, Auburn University
Matthew J. Aresco


Ecology of the gopher tortoise (Gopherus polyphemus) was the subject of my Master’s thesis research at Auburn University. I studied gopher tortoise populations with Craig Guyer in the Conecuh National Forest in southern Alabama on sites that were converted from natural longleaf pine to slash pine plantations in the 1960s and 1970s. I specifically focused on growth and age of the gopher tortoise, burrow dynamics relative to habitat characteristics, and habitat selection by juveniles. The overall goal of this research was to improve management of gopher tortoise habitat on lands managed primarily for forestry and to better understand the implications of certain forest management practices on gopher tortoises.

 

Poor gopher tortoise habitat - 
dense slash pine plantation
Conecuh National Forest, Covington County, Alabama
Optimal gopher tortoise habitat - 
open longleaf pine-wiregrass habitat
Ichauway Plantation, Baker County, Georgia

Below are the abstracts of two papers published from the major results of this research.
 

Aresco, M. J. and C. Guyer. 1999. Burrow abandonment by gopher tortoises in slash pine plantations of the Conecuh National Forest. Journal of Wildlife Management 63:26-35.
 Abstract: We investigated burrow dynamics and factors associated with abandonment of burrows by gopher tortoises (Gopherus polyphemus) in mature slash pine (Pinus elliottii) plantations of the Conecuh National Forest (CNF) in southcentral Alabama. Our objectives were to determine how frequently gopher tortoises abandoned burrows in pine plantations, if burrow abandonment was associated with changes in vegetation conditions, and how rapidly these changes occurred. Burrow survey data collected over 5 years indicated gopher tortoises abandoned burrows at an average rate of 22%/year. We believe burrow abandonment occurred frequently in pine plantations, primarily in association with a change in overstory structure that shaded active burrows. Abandoned gopher tortoise burrows had greater total basal area (P = 0.012), hardwood basal area (P = 0.016), and tree density (P = 0.003) than did active burrows. There was a significant positive correlation between age of active gopher tortoise burrows and canopy closure (total basal area: P = 0.19, P = 0.007; pine basal area: r2 = 0.20, P = 0.004; tree density: r2 = 0.14, P = 0.018). We estimated that overstory conditions at newly active burrows changed to those observed at abandoned burrows in only 5-7 years. Increases in total basal area to 70 m2/ha and tree density to 1,400 trees/ha were associated with burrow abandonment. Active burrows had greater total plant cover (P = 0.009) and grass cover (P = 0.016) than did abandoned burrows. However, we found no correlation between age of active burrows and structure and composition of ground cover vegetation (r2 values ranged from 0.00 to 0.07; P-values ranged from 0.096 to 0.987). Stand thinning to a basal area of 30 m2/ha and prescribed growing-season burns should improve habitat quality, thereby increasing burrow fidelity of gopher tortoises.


Aresco, M. J. and C. Guyer. 1999. Growth of the tortoise Gopherus polyphemus in slash pine plantations of south-central Alabama. Herpetologica 55(4):499-506.


 Abstract: We examined growth patterns of gopher tortoises in slash pine plantations using recapture data from a five-year period. Growth data were fitted to the von Bertalanffy and logistic asymptotic growth models. The von Bertalanffy model provided the best fit to the recapture data. Gopher tortoises grew more slowly than they did in any other published study and were estimated to require at least 20 years to attain sexual maturity Intensive soil disturbance associated with site preparation and conversion to pine plantations in the 1970's destroyed much of the native ground cover. Therefore, slow growth, which resulted in delayed maturity, was attributed to poor forage quality of sparse ground cover vegetation, especially legume and nonlegume forbs. Our study provides evidence that anthropogenic activities associated with historic widespread conversion of longleaf pine habitats to pine plantations may continue to impact current gopher tortoise populations.