Basking Turtles (Painted, Red-Eared Slider, Red-Bellied Cooter)
Pseudemys rubriventris, Chrysemys picta, Trachemys scripta
Did you see that turtle before it slipped into the water?
Maybe it was too far away, and all that you saw was a round black turtle. Maybe you caught a glimpse of some yellow or red markings on its head and neck. Now you see it swimming at the surface, its head poking out of the water, looking at you and waiting for you to go away before it climbs back out. What was it?
Our waterways are full of turtles. Several of these species bask in the sun, making them more accessible than when they are swimming or resting under the water.
Three species account for most of the turtles you see basking in Philadelphia (a few species like map turtles are uncommon, other common species like snapping turtles don’t bask very often)
They look pretty similar at first glance: black, round turtles with a lot of size overlap. Males of all three species are smaller than females, so that a mature male redbelly turtle or red-eared slider can be about the same size as an adult female painted turtle. A lot of the time you might not be able to tell which one you’re looking at, but with a little practice you can learn to tell them apart and study their habits in the city.
The painted turtle is a mostly-black turtle with red markings along the edge of the shell. They have red and yellow stripes on their legs and neck, but on a basking turtle you’ll most likely be able to see the yellow stripes on the head. Painted turtles often have noticeable pale lines on their shells where their scutes (the sections of the shell) meet. They are a little flatter than the other basking turtles you are likely to see. These are the smallest of our basking turtles (females top out with 8 inch shells), though a large painted turtle will be the same size as a small individual of the others.
The red-bellied cooter has thin yellow stripes on its head and neck and orange or red on the visible parts of the plastron (the bottom of the shell). The carapace (upper shell) usually appears to be an even black, but on close examination you might see bars of reddish color. Older turtles will lose the yellow stripes on the head, making them appear to be solid black. Mature female redbelly turtles are our largest basking turtles, with shells topping a foot long. Their shells look streamlined in profile, though not as flat as the painted turtles’.
The red-eared slider usually has a red stripe along the side of the head and yellow stripes along the neck. The shells of basking turtles usually appear to be solid brown or black, though you might notice some yellow lines patterning the carapace as well as yellow color on the plastron. Older turtles can lose the distinctive red stripe. Their shells appear to be comparatively un-streamlined, often with a slightly lumpy appearance. Females can have shells up to about 10 inches long. There is a closely-related yellow-bellied slider that lacks the red head stripe and instead has a thick yellow chinstrap running up its jaw.