Thursday, November 24, 2011

This Thanksgiving, Don’t be a Hog (Nosed Snake)

   Many of us tend to overeat during Thanksgiving, but we've got nothing on snakes, some of which might occasionally eat something larger than they are. When eating a large meal, consuming something bigger than yourself isn’t simply a matter of whether you want to do it; there are also serious physical concerns. In other words, even if you wanted to eat more than your body weight in food (on some Thanksgiving pasts, I’ve certainly given it a fair shot), how can you possibly fit it into your body? Something that weighs more than you do is probably larger than you, and it takes some imagination to figure out how you can fit a large object into a smaller object. One potential is by chewing your food very well, so that you can maximize your ability to arrange your food once you’ve swallowed it. Another option is to select very dense food to eat because a smaller amount of food will weigh more than other, less-dense items. I’ve had some stuffing that might have qualified.

   When eating large prey, snakes have an advantage. Most people know that the unique morphology of a snake’s jaw allows it to go big at mealtime. But, there is a common misconception that snakes can dislocate their jaw, this is not entirely true. What’s unique about snakes is that their lower jaws aren’t connected to each other at the front by bone (like ours are) they are connected by a ligament. This gives them tremendous flexibility in moving their jaws when swallowing food.
A Very Young Hognosed Snake
(not the one mentioned on left)

   But, even though snakes can eat relatively large meals, that doesn’t mean they eat things larger than they are. In fact, a recent study suggested that nobody had ever documented a snake eating something larger than itself, at least when the meal was a frog.

   So, although I’ve seen a bunch of snakes so full of food that they look they’ve been blown up like a balloon, when I trapped a small Eastern Hog-nosed Snake in a bucket in the Florida panhandle, I knew it took the cake. Actually, in this case it looked like it had taken the cake and eaten it.

A Bucket Trap (Note the Pigmy Rattlesnake)
   In 2009 and 2010 I was trapping animals in longleaf pine forests to characterize the wildlife populations there and determine how they responded to different forest management strategies. The type of trap I used is relatively simple; I put aluminum flashing in the ground and bury buckets alongside this makeshift wall. As animals crawl around the ground, they hit the fence and fall into a bucket. It was possible that the Hog-nosed Snake I found had eaten a big meal and then been trapped, but it was so fat I don’t think it would have been moving around much. My guess is that there was a large frog in a bucket, and the snake had crawled in after it.

   I gingerly held the snake and gently placed it into a pillowcase while being careful not to stress it out. When a snake with a recent meal is stressed, they will often regurgitate. It’s likely that the snake can crawl away faster without the added burden. In any case, despite my gentle touch, the small snake did end up throwing up their prey, a Spadefoot Toad. The toad was very much alive.

Spadefoot Toad
   Because snakes can’t chew their food, they swallow it whole. And many snakes don’t constrict their prey before swallowing it, they just start swallowing. That means the prey is often alive when they go down the hatch. Hog-nosed snakes are such a snake. They are frog specialists and they don’t constrict, and that means that if you catch a recently-fed snake, there’s a reasonably good chance that it will cough up a living, breathing frog.

   In this case, I was able to weigh both the toad and the snake, and, as I suspected, the toad actually weighed more than the snake. But, not by much, the toad (36 grams) weighed 1.06x more than the snake (34 grams). After talking to a friend of mine, he noted he had once seen something similar. In his case, he had found a 6 gram Eastern Hog-nosed Snake that had eaten an 8 gram Southern Toad (a ratio of 1.33!). So, if you hope to emulate a Hog-nosed Snake today and eat more than your weight in mashed potatoes and cranberry sauce, just remember that the stuffed snakes we caught weren’t able to keep their meals down. You probably won’t either.

Happy Thanksgiving

Relevant Scientific Articles

Toledo, L., Ribeiro, R., & Haddad, C. (2007). Anurans as prey: an exploratory analysis and size relationships between predators and their prey Journal of Zoology, 271 (2), 170-177 DOI: 10.1111/j.1469-7998.2006.00195.x

D. A. Steen, G. G. Sorrell, N. J. Paris, K. J. Paris, D. D. Simpson, & L. L. Smith (2010). Heterodon platirhinos (Eastern Hog-nosed Snake). Predator/prey mass ratio Herpetological Review, 41

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