KEYWORDS: endanagered turtles threatened turtles red bellied turtle yellow-blotched sawback turtle Pascagoula River turtles Leaf River turtles Chickasawhay River endangered turtles turtle breeding habits determine sex of turtles Mississippi turtle
AUTHOR: Sara Greer
Within the boundaries of the largest unimpeded waterway in the continental United States, hidden deep in boggy marshes and thick woodlands, many species of plants and animals struggle for survival.
According to the Mississippi Department of Wildlife, Fisheries and Parks and the Mississippi Museum of Natural Science, the state is home to 80 species and subspecies of plants and animals that are federally recognized as threatened or endangered. More than 20 of those live in the Pascagoula River ecosystem.
The yellow-blotched sawback turtle is unique among the endangered plants and animals because it is only found in South Mississippi. Endemic to Mississippi, this threatened turtle is only found in the Pascagoula, Leaf and Chickasawhay rivers, where it loves to bask in the sun.
“These guys don’t like shady streams, so if you’ve got a stream that has trees that form a closed canopy you’re not going to find yellow-blotched there,” said Bob Jones, a herpetologist with the museum.
The turtles’ picky nature enhances their chances of survival.
“Basking raises their body temperature. If you’re a female turtle, it helps you to develop eggs and if you’re a turtle in general it helps with digestion,” he said.
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Temperature also determines the sex of yellow-blotched offspring. Warmer temperatures produce females and cooler ones produce males.
“The difference between those two temperatures is often like two or three degrees. It’s not much,” Jones said.
Incubation temperatures, combined with human encroachment on nesting sites, are among the reasons the sawback is threatened.
“What’s been happening is that when these sandbars are occupied by humans all day, there’s no sunny places,” he said. “The female turtle goes to a shady spot.”
This behavior skews the sex ratio.
“You’ll have just a very few females and a whole bunch of pretty males doing absolutely nothing,” Jones said. “They need some nice, pretty places like that so they can produce a balanced sex ratio.”
Biologist Tom Mann said scientists don’t have specific population numbers, he said.
“We do know in general terms that the largest population left in the Pascagoula River is in the vicinity of Vancleave, and as you go further upriver the density of turtles becomes lower,” he said.
Mann and others set out in the 1990s to determine whether red-bellied turtles in the Pascagoula were similar to those in neighboring Alabama. The latter species was federally protected at the time.
“We have recently published a paper in which we formally combine this one with the one in Alabama,” Mann said. “So it is now formally protected as a federally endangered turtle.”
Unlike the yellow-blotched sawback, he said, the Alabama red-bellied turtle prefers “side channels and pockets off the main river.
“We know it’s found in the Escatawpa drainage, the Pascagoula drainage, and in the several Back Bay tributaries including Old Fort Bayou, the Biloxi River and the Tchoutacabouffa,” he said. “We suspect it’s in a few more little tribs as well, and we don’t know how far up it goes the Pascagoula.”
Alabama red-bellied turtles were listed as federally endangered in 1987, largely because of human encroachment on habitat, incidental capture by commercial and recreational fishermen and pet trading.
“They use uplands for nesting, and whenever you put in a seawall or boat slip, and you armor those to keep waves from eroding those, you’ve denied access to something which has to periodically crawl up into some place,” Mann said.
Barricaded from their natural nesting grounds, the turtles take another route, through bayous like Mary Walker and across busy roads, to uplands that are increasingly subject to human development.
“Situations like that pose a threat of unknown significance,” Mann said.