I learned about this from a Facebook post that algorithms randomly chose for my feed. Chris Gillette manages the Bellamy Acres Animal Sanctuary where injured wild animals are nursed back to health and released back into the wild, if possible, and he shares results on Facebook. This post was about an alligator snapping turtle they restored to good health but couldn’t release to the wild because it was not from the correct river drainage. Apparently, someone had captured the turtle and didn’t return it to its river of origin. At first the decision not to release it back into the wild didn’t make sense to me. Why not improve the genetic vigor of the population? I didn’t know that in 2014 scientists determined there were 3 different species of alligator snapping turtles. The study was published in a really obscure scientific journal and didn’t get much publicity, so no wonder I was ignorant of it.
Former range map of alligator snapping turtles. The soup industry extirpated them from the northern parts of their range.
Map showing where specimens of alligator snapping turtles were sampled in the below referenced study. The different colors represent different species.
The 3 species differ anatomically. They have different sized caudal notch areas in the rear of their shell. Photo from the below referenced study.
The 3 species also differ in the angle of the squamosal region of their skulls. Photo also from the below referenced study.
The wormlike tongue of the alligator snapping turtle lures fish to their doom.
The scientists who published this article looked at the anatomy and genetics of 93 alligator snapping turtles from the Mississippi River and Mobile Bay Drainage systems, 17 from the Apalachicola River Drainage, and 18 from the Suwannee River Drainage. They determined from genetic evidence that Western alligator snapping turtles (Macrochelys temminckii) diverged from Apalachicola alligator snapping turtles (M. apalachicola) 5.3-13.4 million years ago. The latter diverged from the Suwanee alligator snapping turtle (M. suwanniensis) 3.2-8.9 million years ago. This is quite a difference in their genetic ancestry. Unlike common snapping turtles (Chelydra serpentina), alligator snapping turtles don’t disperse great distances over land. (I’ve seen common snapping turtles a considerable distance from any body of water.) Therefore, these populations of alligator snapping turtles became genetically isolated from each other a very long time ago. Sometime during the middle of the Miocene, the Mississippi River and the Apalachicola Rivers must have been connected but became geographically separated, and the same must be true for the Apalachicola and Suwannee River systems. The study suggests ancestors of alligator snapping turtles diverged from common snapping turtle ancestors at least 17.5 million years ago.
The study also found that purported fossils of alligator snapping turtles from the peninsula of Florida dating to the early Pleistocene were probably an extinct species of giant common snapping turtle. Sea level rise during an Interglacial caused the extinction of this yet to be named species.
These 3 species of alligator snapping turtles differ anatomically as well. They have different sized notches on the back of their shells, and the angle of the squamosal region of their skulls differs.
All 3 species of alligator snapping turtles are endangered, and the western alligator snapping turtle was extirpated from the northern part of its range because Campbell’s soups used them for their turtle soup during the 1970s and 1980s. This is a shame. They are fascinating long-lived creatures that unfortunately breed slowly. Some live alligator snapping turtles have been found with musket balls and Indian arrowheads embedded in their shells, demonstrating just how long they live. They grow up to 200 pounds, growing fat by luring fish to their doom with their worm-like tongue.
Reference:
Thomas, T. ; M. Granatosky, J. Bourque, and K. Krysko
“Taxonomic Assessment of Alligator Snapping Turtles (Chelydridae: Macrochelys) with the Description of Two New Species from the Southeastern U.S.”
Zoo Taxa 3786 (2) 2014
GeorgiaBeforePeople 