As many of you may know, the Georgia Sea Turtle Center has had a significant amount of diamondback terrapin hatchlings (280 since our doors opened in 2007!). What some of you may not know is how we get these little turtles. During the spring/summer (May-July) nesting season many females are hit by cars while attempting to find high and dry ground to nest on. Some females aren’t hit until crossing back over the road (and thus have no eggs to collect). The terrapins that are hit when crossing the road the first time still have eggs in them. Most of the time eggs are completely crushed when a female is hit by a car, however it’s still not uncommon to see a hit female that still has intact eggs. In 2012 we found that 29.6% of hit females that hadn’t nested before being hit still had intact eggs.
We bring all injured and dead females back to the center and if they have eggs we will collect them from her. Terrapins that are still alive are induced with Oxytocin after they are stable so that they will lay their eggs naturally. Once we have the eggs in hand we will take measurements (mass, length and width) and place them in an egg container filled with a substrate.
These egg containers are then placed in our incubators and the eggs are checked periodically for signs of mold, non-viability, and hatching.
Terrapins, like all other turtles, display temperature dependent sex determination. Male terrapins are produced when incubating eggs at temperatures below 82˚F and females above 86˚F. Between these two temperatures a mixture of genders will appear in a clutch. In order to make up for the loss of females on the causeway and to help aid the 4:1 male biased population around Jekyll (most likely caused by female road mortality) we set the incubators at 86-87˚F.
This year we hatched 44 terrapins between July and August for our rear and release program.
Once they hatch they are monitored for a week while their umbilicus (the remnants of the yolk sac) absorbs into their body.
From there they are put into small white tubs with water and the salinity is gradually increased.
Once they are eating well they will be put in a larger display tank. For the next 8 or 9 months these girls will be cared for and monitored. The goal is to get them to a substantial size so that they have a greater chance of survival in the wild (this is especially important for turtles). The hatchlings are fed a combination of krill, turtle pellets and reptomin every day in individual containers so that we can monitor their food intake. Most are pretty voracious and start to grow pretty fast! They grow so fast in fact that we can’t keep them all in our display tanks. We have to make larger tanks for them and as time passes we start to add natural plants to their tanks and offer them small fiddler crabs (a main food source for wild terrapins).
Finally, from May-June we will systematically release all of our hatchlings into the wild as our next batches of eggs begin to come in to start the whole process over. There is nothing more gratifying than watching these animals that you’ve cared so long for, from the first time you saw them on the road still in their egg, to witnessing their birth as they poke their head out of the shell, to watching them swim, eat, and grow, being released back out into the marsh.
For all this work, our goal is simply to collect eggs that would not otherwise hatch, rear the hatchlings, and release them to help minimize some of the damage to the local population by ensuring that at least some of the young survive. This is not to say that hatching terrapin hatchlings will make up for the losses however. Sadly, even though we have managed to raise 44 hatchlings, 130 adult females died on the causeway last summer. Even if every one of the 44 makes it to maturity, it still will not make up for even half of the losses. Adding to this fact is that adult females are the most important demographic in turtle populations since they take the longest to reach maturity, can reproduce for many years and are less susceptible to predators. Losing one adult female terrapin could actually mean losing upwards of 30 future clutches and, with an average of 8 eggs per clutch, this equals 240 potential hatchlings. Yes, 1 Adult = 240 hatchlings. This is about how many hatchlings the center has released since its inception. We have seen 944 female deaths on the causeway since 2007 (given what one female can lay in a lifetime and given that not all of them are first year nesters, this is equal to 113,000 potential hatchlings minimum since 2007 that never made it). These sobering facts demonstrates that increasing hatchlings in the wild, while important, is not the grand solution for conservation of the species. Rather, conservation involves considering a suite of variables. For diamondback terrapins around Jekyll, we must focus on increasing the number of hatchlings and reducing the female mortality through mitigation research, public education/awareness, rehabilitation of injured females and rearing of hatchlings.
-Dan Quinn (Diamondback Terrapin Member)