Giving birth is never an easy feat, but it's an especially tricky process for the critically endangered spider tortoise. That's why herpetologists at Smithsonian's National Zoo were so excited when a tiny spider tortoise hatched from its shell earlier this month.
Last January, a wild-caught breeding pair of spider tortoises were brought to the zoo under the recommendation of the Association of Zoos and Aquariums' Species Survival Plan. The goal was to breed the pair, which had been in captivity for more than 10 years, to diversify the gene pool of captive spider tortoises.
But it's not a simple task, according to Lauren Augustine, a reptile keeper at the zoo. Augustine told me spider tortoises only lay one egg at a time, up to three times a season. Those eggs are in a state of diapause: a kind of stasis to protect the egg from developing until the environment is favorable for a young hatchling to survive.
"Often in the wild they go through a cold period after the egg is laid. So the egg won't start developing until conditions are more favorable," Augustine said in a phone interview.
Favorable conditions are when it's warm enough that the hatchling won't freeze and will have access to plenty of vegetation for food and camouflage, she told me.
"So you need to kind of spark the egg out of this diapause," Augustine said.
To do this, the zoo takes the egg and puts it in an incubator to keep it warm. If they don't see any signs of development, they'll slowly cool the egg down to simulate a cold snap. Then, after a few weeks, they bring the temperature back up.
Every zoo does this process slightly differently, Augustine said, so the team at the National Zoo took a look at what steps worked well at other zoos the past to create a kind of best practice for incubating these delicate eggs.
They tried incubating this egg after it was laid back in September, but weren't seeing any success, so the herpetologists cooled it down to 60 degrees Fahrenheit for seven weeks. They then put it back into incubation and, in March, saw the first signs of development. On May 10, the little hatchling emerged from its shell. It's too soon to tell the sex of the tortoise: they all look the same when they're this young.
This was the second of three eggs that the mother tortoise has laid so far. The first never hatched—Augustine said they tried the cooling and warming process but suspect that egg just isn't fertile—and the third is currently being incubated.
"It's awesome," Augustine said. "We're just super excited about it here. It's a big deal for us to be able to do it in our first year."
In the wild, the spider tortoise is disappearing at an alarming rate. Destruction of their natural habitat combined with poachers capturing the tortoises to sell in the Asian food market has caused an 80 percent drop in spider tortoise populations over just a few generations of the species. Augustine said some conservationists estimate the tortoises could be completely extinct in just 10 years.
That's why it's so important to keep a healthy, genetically diverse population in captivity, Augustine said. It may not be an easy task to get these eggs to hatch, but if the rapid decline of the spider tortoise in the wild continues, it could be our only hope for preserving the species.