Wednesday, March 14, 2012

Readers Write In: What is Eating this Dead Snake?

Today I received the following e-mail from a reader in Florida:

"We had a 5 foot snake in our back yard which our yard man killed and then left it.  My husband did not get the chance to discard of it and today when we went out to remove it there is something that is pulling it into the ground.  It was a good size snake and it fits right into the hole.  We saw the tip of the legs of the animal doing the pulling and it almost looked spider or crab like.  We live in Merritt Island, Fl and are across the street from a small wooded area which sits along the river. Between us and the river is also a very busy road.  I am wondering if you have any idea what kind of creature could be living underground and likes to eat a dead snake.  I hope you can come up with an answer for us because we are stumped.  Thanks for your time.

Brooke H.
Merrit Island, Florida"

This was a surprising question for me because I was not asked to identify the dead snake! After receiving this e-mail, I immediately thought of carrion beetles. This group of invertebrates has some unique reproductive strategies. Some of these insects, after locating a dead animal, will bury the carcass and lay their eggs on it. When the eggs hatch, the young are provided with a ready food source. This information was fresh in my mind because just a few months ago I conducted some background research on the topic. Super-naturalist (and fellow blogger) Dirk Stevenson recently observed a number of dung beetles (which may just eat dead things and not necessarily lay their eggs in them) feeding on a watersnake carcass and we concluded it was the first time this behavior had been observed between these species.

Dung Beetles Feeding on a Watersnake, courtesy D. Stevenson
I contacted Dirk to confirm my suspicions and he agreed that the culprit could have been been a carrion beetle. But, he suggested I focus on the fact that the animal appeared crab-like. There are, after all, crabs that love to eat dead things.

I followed Dirk's advice and my research quickly led me to the Blue Land Crab, Cardisoma guanhumi, which can be found throughout much of coastal Florida. These large crabs can live relatively far from the ocean (but often inhabit areas near river banks) and they inhabit deep tunnels (up to six feet, according to this link). Basically, the crabs make their tunnels as deep as needed to reach water, which pools on the bottom. Although they live much of their lives in these tunnels, Blue Land Crabs return to saltwater areas to breed. 

Blue Land Crabs feed largely on plant-matter, but they are omnivorous and are known to drag dead things back to their burrow, where they can eat in safety. I think a large Blue Land Crab would be very interested in a fresh snake carcass and I believe this is what Brooke observed in her backyard. Do all the Florida crustacean biologists agree?

Blue Land Crab (Creative Commons License)


Want to Learn More? Check out the Following Scientific Articles:

Gifford, C. (1962). Some Observations on the General Biology of the Land Crab, Cardisoma guanhumi (Latreille), in South Florida Biological Bulletin, 123 (1) DOI: 10.2307/1539516

D. J. Stevenson, D. A. Steen, & M. Wallace (2012). Nerodia erythrogaster erythrogaster (Red-bellied Watersnake). Necrophagy by dung beetles (Scarabaeinae). Herpetological Review

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