Friday, November 15, 2013

Life in the Slow Lane: A Profile of the Gopher Tortoise

By Laurie Sheldon

Gopher tortoise entering burrow; photo by Gary Foster.
Joseph Butler, a U.N.F. Biology Professor and herpetologist, was a guest speaker at one of  the Ixia chapter's recent meetings. He hoped to study snakes when he moved to Florida, but found that they were hard to pin down, so to speak. He turned his attention to Gopher Tortoises, which proved to be a much more reliable subject to study, as they live long lives (50 years +) and there are over 400 burrows on campus.The gopher tortoise is federally protected as a threatened species except in Florida, where it is listed as a Species of Special Concern by the Florida Fish and Wildlife Conservation Commission.

Gopher tortoises (Gopherus polyphemus) are native reptiles that can be found throughout the southeastern U.S.. They prefer sandhill communities, which are typified by longleaf pines and turkey oaks growing in loose, sandy soil. Much of the longleaf pine in Florida has been replaced with slash pine, which grows significantly faster; the unfortunate byproduct has been a loss of 80% of the gopher tortoise's habitat. As these reptiles are primarily herbivorous, they depend on fire to open up the canopy and let in sunlight for understory plants to grow. Fun fact: gopher tortoises do not eat during winter.

Gopher tortoises copulating; photo by Stephen LeQuier.
Their thick claws and strong forelimbs are excellent tools when it comes to digging their burrows to live in, which can be 30' long and 18' deep. Not only do their burrows provide them with temperature control and some degree of protection from predators, but they are also used as shelter for over 300 other species of animals. As such, gopher tortoises are considered to be a "keystone species". The area around the burrow opening is called the apron. It is the happening place for gopher tortoises, as that is where courtship, mating, combat, and egg laying occurs. It is presumed that they choose a location based on the availability of vegetation nearby. Each gopher tortoise has its own burrow. Not all burrows are active. Tracks are usually a giveaway that someone's home. When there are no tracks in sight, a simple way to tell if a burrow is active is to place a stick in front of it (if a tortoise is living there, it will move the stick).

Concave male plastron above. Flat
female plastron below. Photo from
http://www.gophertortoise.org/ .
Males and females are about the same size (11" long). The top portion of their shell is called a carapace, and the lower portion is a plastron. The way to tell them apart is to turn them over. The males have a concave plastron, which enables them to copulate. Gopher tortoises don't reach sexual maturity until they are 12-15 years old, so it's critical to the future of the species for them to be protected until they are old! They mate during spring and typically lay 4-7 eggs sometime between the second week in May and June. Eggs take 70 days to incubate; accordingly, hatching occurs sometime in August or September. Because their shells remain soft for 7-8 years, they are easy prey for hawks, etc.

Tortoise hatching from its hard egg;
photo by Mike Simmons
To monitor the tortoises on campus, Dr. Butler and his team would dig a hole and place a bucket in it just in front of the apron. When the tortoise fell into the bucket, they would measure and weigh it, then set it on its merry way. Tortoise babies are difficult to find. They use their umbilicus for food during the first year of their lives, so they have little reason to wander. As such, it is easier to study them from the egg stage, let them hatch, then equip them with radio-telemetry to keep tabs on them. Where most reptile eggs are leathery, gopher tortoise eggs are hard, and will make a clicking sound when tapped. Dr. Butler attempted to find eggs by listening for that click while probing the ground with a construction-type flag. The problem with this method: rocks also click when tapped... and back to the drawing board he went.

Have you seen a gopher tortoise or a tortoise burrow before? Here's a story by Peg Lindsay about her up-close and personal encounter with the species:

Wildflower gardens have a totally different “look” to them. They’re usually not showy, manicured nor neat. Mine is no exception. My husband and I had intended to trim back the dead stems and apply leaf mulch in the fall, but we noticed Goldfinches perching on the dead stalks snacking from the seed-heads, and Cardinals, Mockingbirds and Palm Warblers scratching through the leaf litter for their dinner. We decided to let it be, through the winter. It was . . . um . . . unattractive. At least it wasn't in the FRONT yard.

When the weather warmed up, new sprouts began to poke through the sand, and all danger of another freeze had past, we decided it was finally time to clean up the mess. That's when we noticed a Gopher Tortoise hole right smack in the middle of our garden. It was about 8 inches wide by about 5 inches high – definitely sized for a youngster. We proudly showed it to anyone who wandered by.

Young gopher tortoise photo by Melody Hendrix.

Both the tortoise and its burrow are protected under state law, so we had to manage our garden while protecting the hole. I was nervous about disturbing it, so I spoke to a friend of mine who has several of these critters in her yard. She said that I can go ahead and plant and weed around the burrow. She also told me that they are opportunistic eaters - although they are primarily vegetarian and will eat just about any plant which grows in Florida, they also snack on insects and other tiny creatures. The variety of native grasses and wildflowers in our garden may have been what attracted the tortoise to begin with!

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Additional information:
FWC on Florida’s Gopher Tortoise
For young readers:
The Gopher Tortoise – A Life History
At Home with the Gopher Tortoise: The Story of a Keystone Species

2 comments:

Ricklefs Family said...

Good afternoon - hope this finds you well this weekend.

Our daughter found a baby gopher tortoise beer our home in FL. She fell in love with I'm and named him Spots. Once we realized the exact kind of tortoise he was, we retuned him to the wild.

She has now written about about Spots the Tortoise and is running a Kickstarter campaign to help raise the necessary funds.


Here is her campaign, we have about $2,000 to go. http://kck.st/1ghcfgl

Any help you can give us in spreading this message, we would be extremely grateful.

Thanks a bunch,

Justin Ricklefs

The Jolly Bloggers said...

I think that's terrific and I just checked out the kickstarter page - I'm very impressed with what your daughter has learned and expressed. I think the book would be much better if SHE did the illustrations, rather than paying someone else to do the work - particularly someone out of state. Just something to think about. I'll share the link to her campaign on our Facebook page. Hopefully some of our 6,300+ members will chip in. If so, a nod to us somewhere in the book would be a lovely gesture. Good luck!