Differentiate between Marsh Terrapin and Hinged Terrapin

[Sfourie]

Hi All,

I am Field Guide Student studying through WildlifeCampus. Although I enjoy all components of the study I am currently busy with the really fun part, yes you guessed it: Reptiles.

For the last month I have been hard at work on chelonians and I hope to be finishing with the component next week. There is however still a part of chelonians that I just cannot master; How to differentiate between a Marsh Terrapin and Hinged Terrapin. Both have 5 vertebral scutes and four pairs of coastal scutes and 11 marginal scutes on each side. Both lack a nuchal scute. I thought patterns on the head may be an ID point yet it seems some individual Marsh Terrapins has patterning on the head very similar to some of the Hinged Terrapins. Johan Marais suggests looking at the profile of the carapace and yes the Hinged Terrapin has a bit more of a dome shape to it's carapace but I would like something more definitive.

Is there something that I have perhaps overlooked, any advice would be appreciated.

Regards

Stefan

[Westley Price]

Well that depends on your needs.

Do you want to ID it from a distance or in-hand?

In hand it should be easy enough. As the name states, the Hinged Terrapins have a plastral hinge (on the belly).

That should be the easiest way to tell the difference.

Note that I have not seen Hinged Terrapins in person so I'm just basing my answer on literature.

From a distance I guess it's not so easy.

[Sfourie]

That is the problem Westley as a Field Guide you are obliged to minimize contact with the animals. As an ordinary Field Guide you would have no realistic chance of studying one in-hand, as a Trails Guide there might be a slim chance though it would probably be considered unethical. I am still a greenhorn in the industry but as I understand it contact with specifically chelonians - especially tortoises - is a strict no-no.

[Westley Price]

I found the following post on a Turtle forum which I think might help you:

http://www.turtleforum.com/forum/upload/index.php?showtopic=80160

It has some great comparison shots between the Hinged terrapins and March terrapins.

There are some subtle differences in the dorsal scutes which are easier to see in the comparison shots, but are still quite subtle so it might be difficult from a distance.

To me, the most obvious difference from these pictures is the terrapins' "shells" around the neck region. In Pelomudusa it appears scalloped, while in Pelusios it forms a straight edge.

This should be visible from a distance using binoculars.

I hope I have helped a bit.

[Sfourie]

Hi Westley,

What a great helpful article, glad to see I am not the only on struggling with this. Thank you very much for your help; you are a great asset to SA Reptiles. It would also seem that the Hinged Terrapins have shorter proboscis than the Marsh Terrapin.

What beautiful coloration that Yellow-bellied Hinged Terrapin has on its carapace.

Regards

Stefan