By Dirk J. Stevenson
The venerable gopher tortoise is one of the best known and most charismatic inhabitants of our longleaf pine/turkey oak sandhill habitats. A keystone species, the tortoise is of inestimable importance to this ecosystem.
Peek into a gopher tortoise burrow and you might come nose to nose with an ancient reptile. Meet the gopher’s contemplative gaze. Admire the time-worn carapace (gophers reach sexual maturity at about 20 years old in Georgia and may live to more than 80 in the wild). Ogle the massive, scaly forepaws, shaped like oars and used to scoop miniature mountains of sand from the earth.
Place your head near the entrance of the burrow and draw a deep breath. Because gopher tortoises usually defecate inside, the smell of an “active” burrow is strong and distinctive, a hot-house odor of decomposing grass (a bit like the elephant house at the zoo).
Burrows of adult gophers are right impressive – on average 6-10 feet deep and 15-20 feet long. The burrows approximate the size of the resident gopher, being just tall and wide enough to allow the occupant to turn around inside. Burrow aprons, the sandy pile of yellow spoil at the mouth, formed as sand is pushed skyward by the industrious reptile, can be larger than the hoods of late-model Cadillacs. Individual burrows, sometimes adopted or renovated by successive gophers, may exist for decades.
Deep, dry but humid and thermally-stable, gopher tortoise burrows are like caves – stable environments. The depths are warmer than air temperatures in the winter and cooler in summer. Thus, it is not surprising that hundreds of wildlife species use gopher tortoise burrows: for winter dens, to escape from predators, to avoid fire or temperature extremes, for foraging, for nest sites, and for shelter while shedding their skins (snakes) or undergoing metamorphosis (insects).
For a number of invertebrate species, the relationship may be obligatory. That is, there are species of beetles, moths and flies found nowhere else on the globe except the burrows of Gopherus polyphemus.
These are often referred to as “obligate commensals.”
We’ll take a closer look at these creatures in the next post. But first, a few insights into a special source of the tortoise burrow’s diversity, plus some best-of quotes about burrows.
Dirk J. Stevenson is a naturalist and owner of Altamaha Environmental Consulting.
Bonus Feature: Burrow Food Web
The unique food web associated with occupied tortoise burrows is the energy supplied by fresh tortoise dung. The dung is coveted by coprophagous crickets, scarab beetles and anthomyiid flies. These insects, in turn, are prey for staphylinid beetles, the tortoise burrow robber fly, southern toads and gopher frogs. And up the ladder we go. The big eastern indigo and coachwhip snakes forever going in and out of tortoise burrows commonly forage for snakes, amphibians and rodents when visiting the burrows.
Bonus Feature: Quoteable
Early naturalists wrote with wonder about gopher tortoise burrows.
The dens, or caverns, dug in the sand-hills, by the great land tortoise, called the Gopher, present a very singular appearance: these vast caves are their castles …
William Bartram, 1791
“Travels of William Bartram”
The gopher snake (Spilotes corais) goes in and out the burrows and the gopher frog (Rana aesopus), also on friendly terms, sits in the doorways at dusk.
Theodore Roosevelt, 1917
“Notes on Florida Turtles,” American Museum Journal Vol. 16(4): 288-293
After excavating a long adult tortoise burrow, “so large a pit had been dug that a coach and span of horses might have been swallowed up in it.”
Henry Hubbard, 1894
“The insect guests of the Florida land tortoise,” Insect Life 6(4):301-315
The open mouth of the burrow is a blanket invitation to any animals with cavernicolous tendencies, and the supply of dung at the bottom is an added attraction to coprophages.
F.N. Young and C.C. Goff, 1939
“Annotated list of the arthropods found in the burrows of the Florida gopher tortoise,” Florida Entomologist 22(4):53−62