black mamba

It's one of two very similar species - either the Northern Watersnake (Nerodia sipedon) or the Blotched Watersnake (Nerodia erytrhogaster). Both of these are common, non-venomous water snakes that are found around ponds and streams in the Tulsa area. Because the head looks fairly narrow and dark, I suspect that it is probably a Northern Watersnake. The best way to distinguish between the two species is look at the belly - the Blotched Watersnake has a plain, yellowish colored belly and neck and this is sometime visible on its sides and when it lifts its head. The Northern Watersnake has an off-white belly with dark brown or reddish-brown half-moon-shaped markings on it.

It is definitely not a Cottonmouth/Water Mocassin because the upper surface of its back shows elongated rectangular markings (Cottonmouths are either uniformly dark or have bands with jagged edges across their bodies), its body it too thin (Cottonmouths are relatively thick snakes) and its head is not broad enough at the base (a Cottonmouth's head is usually shaped like a spade).

All of the watersnakes can be foul-tempered and I don't recommend that anyone try to catch and hold one because they tend to bite, but they are harmless to people and pets. Watersnakes often den/hibernate in groups so it is not too uncommon to see groups of them early in the spring and again in the fall. But as the next few weeks pass, the snakes will disperse and not be as concentrated in large numbers. I suspect that there is a debris pile, log jab or beaver dam in the area where they have spent the winter.

I hope that this helped. Please let me know if you have any other questions,
Mark

Mark D. Howery
Wildlife Diversity Biologist
Oklahoma Dept of Wildlife Conservation
1801 N. Lincoln Blvd
Oklahoma City, OK 73105

We have those also..Have been told they are rat snakes..

http://www.trailquest.net/SNpoi.html
THis site has snakes and links to photos of each.

Based on the patterning this looks like a Nerodia species (probably N. rhombifera) which is commonly called the "diamondback water snake". It is non-venomous.