Thursday, March 28, 2013

Social Snakes

The other day I ran into an interesting blog run by a couple of people who work with rattlesnakes in Arizona. The name of the blog, like the title of this post, is Social Snakes.

Before I explain the reason for the name, I want to note that I consider myself fairly knowledgeable about snakes in general. I'm pretty sure they were my first favorite animal, and I've always loved their stream-lined sinuous shape. I'm familiar with many of the myths about snakes and also with the truth behind those myths.

But I was still taken completely by surprise by the snake behavior the authors of Social Snakes are documenting in the wild. What they are documenting appears to be social behavior in snakes, hence the title. This is pretty much counter to the general consensus about snakes, that they are mostly loners who prefer to be left alone except when mating or (for some species) hibernating for the winter.

Snakes are reptiles, after all, and the majority of reptiles are not especially good mothers. As far as I know, nearly all lizards and chelonians (turtles/tortoises) pretty much just abandon their eggs, and never interact with their offspring at all. On the other hand, the remaining reptiles actually make pretty good mothers; crocodilians are caring and nurturing mothers, building and guarding nests for their eggs, ferrying babies around in their mouths, and ferociously defending them from predators. There's evidence, too, the some dinosaurs at least took care of their egg and made good mothers.

So where do snakes fit in on this scale? Most snakes, or so the conventional wisdom goes, are with the lizards and chelonians; they lay eggs and leave the young to their own devices. The king cobra is currently the only species known to actually defend its eggs after laying them (as anyone familiar with Riki Tiki Tavi will remember), but the mothers abandon the nest right before the eggs hatch, leaving the hatchlings on their own.

However, there's an interesting loophole to this: not all snake are oviparous (egg-laying). Some, rattlesnakes in particular, are ovoviviparous, giving birth to live young. And it's here that the story gets interesting.

You see, the authors of Social Snakes (Melissa Amerello, Jeffrey Smith, and John Slone), have spent several years studying rattlesnakes in the wild, and they noticed some behavior not typically associated with snakes. Rattlesnake mothers were observed acting in ways more usually associated with mammals. The baby rattlesnakes would stick around with their mother for some time after birth, during which time she would actively watch over them and defend them against attack.

There are some tender and touching stories on that blog about rattlesnake mothers actively herding too-adventurous babies back into line with the rest, snakes going from placid and quiet to actively defending their babies and threatening intruders like a mama bear after giving birth, and even a case of one mother herding another mother's babies from going too far away, complex social behavior of a kind definitely unknown among snakes before. Mama and baby snakes would often be seen basking all together in one big pile of snake-y serenity, the darker parents perhaps soaking up extra solar radiation and making it available to their lighter-colored progeny.

Honestly, some of those stories of maternal care are quite touching, and at this point you should probably stop reading my attempts to explain and just go read the blog itself (it's not overly long, at this point).

Interestingly, one of the newer posts on the blog asks why, since people have been observing rattlesnakes for hundreds of years now, no one ever noticed this behavior before? The answer seems to be that, much like everything in science, your paradigm dictates what you will see. People had seen this behavior before, but no one could apparently bring themselves to accept that those repugnant reptiles might actually be showing maternal care for their children, and it was explained away in various manners. It was only by taking a fresh look and suspending previously held biases that these people were able to make sense of their observations and in the process get a glimpse into the secret family lives of vipers.

Well. I didn't intend for this post to end up in a discussion of the philosophy of science, but there you go. If you haven't yet, go and read Social Snakes. If some of those stories don't warm your heart at least a smidgen, well...I'd say you were cold-blooded, but...

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