Turtle Identification - Part 2

After introducing some of the key things to look for in turtle identification, I want to mention the limitations of the identifications I'm doing. Most of these pictures are taken using all the magnification my camera can provide, and they still don't always provide the detail I'd like. Depending on the position of the turtle, I rarely get a view of the plastron, and if I do it's usually at the expense of a view of the carapace. If I could examine the turtle in my hands, I'd be able to do turtle identification a lot better.

Having said that, the 3 middle turtles below provide a very good clue as to what they are. My field guide tells me that the Eastern Painted Turtle is the only species in NJ where "the large scutes are lined up in even rows across the carapace". From left to right, the 3rd and 4th turtles give you a good view of the scutes on the carapace lining up. These are Eastern Painted Turtles.

If you look at the 2nd turtle, the scutes near the front of the turtle clearly don't align, but you can kind of see that the scutes near the rear of the turtle do align. So how does the rule apply if some of the scutes line up and some of them don't? My field guide is ambiguous here, but as far as I can tell looking at other sources, the lined-up scutes is something you can expect to see on the scutes in the rear. It looks to me like the lined-up scutes rule tends to break down near the front of the carapace. So I think we're up to 3 Eastern Painted Turtles now.

Now let's look at the turtle on the left. This turtle clearly has a different carapace as the Eastern Painted Turtles, so I'm ruling that out. This turtle is clearly larger than the EPTs, there doesn't appear to be a keel going along the top of the carapace, and has a very black head. These all point to a Northern Red-bellied Cooter, which is the largest turtle in NJ that basks out of the water. (You wouldn't expect to see a Common Snapping Turtle out there.)

Of course, there are other possibilities. Though my field guide (and other sources) imply they shouldn't live around here, iNaturalist suggests a River Cooter for many turtles like this one. I suspect that a couple of turtles in NJ have been misidentified as River Cooters, or maybe people released a handful that they brought from another area, and now iNaturalist considers the River Cooter as a common NJ resident.

Finally, the Red-eared Slider is another possibility. These turtles are definitely in NJ, and although they're not as big as Northern Red-bellied Cooters, if the EPTs are on the small side and a Red-eared Slider is on the large side, maybe the size difference could work. Red-eared Sliders are supposed to have a red mark on their heads, but my guide does say this is "not always present". And it's considered to be "weakly keeled" - is it possible that a slight keel would be noticeable from a different angle?

I'll say that I'm fairly confident of this ID, but I'm not absolutely certain of it.

I'm not really confident of the turtle on the right. I'm suspicious of a slider or cooter, but I really don't have a good enough look at that one to tell you much.

April 5 at Raritan River Greenway
Photo 120285381, (c) jpviolette, some rights reserved (CC BY-NC)