Some of the most interesting behavior I’ve seen in desert tortoises has involved situations with multiple individuals. Despite wild tortoises readiness to approach humans under certain circumstances, after we mess with them a bit (i.e. attach a transmitter, conduct a health assessment, etc.), they generally have had enough, and will either walk away (and on rare occasions run; a hilarious sight if you’re lucky enough to witness it) or withdraw tightly into their shells until they consider it safe to come out. An exception is if there are two or more tortoises present, as there are occasions when we process multiple animals from the same burrow. In these instances, the tortoise not being processed is generally within view of our activities. Rather than trying to escape, as you might expect, this individual often shows pointed interest in what’s going on. From a few feet away, he extends his neck as far as it will go, and looks on with what appears to be remarkable focus. Every few minutes he may take a few slow, tentative steps closer in what I imagine to be a tortoise’s best attempt at stealth, his gaze never wavering. He may watch for ten minutes or more before eventually deciding to head off.
At times like this I have to wonder who’s really studying who, and what – if anything – is going through these animals’ little heads. Again, I’m baffled by the tortoises’ apparent lack of fear for people. Why would this animal hang around, potentially putting itself at greater risk, after seeing that we had captured its burrow-mate? In these scenarios it can be easy (and let’s admit it – fun) to anthropomorphize. Was this tortoise angry that we had taken his girlfriend? Was he concerned? To a casual observer, this kind of behavior could look a whole lot like empathy, a trait only known to exist in mammals. (For a long time empathy was considered a purely human characteristic; later it was discovered among other primates, and most recently a study has revealed that even mice empathize). Non-mammals (including herps) do, however, exhibit behaviors such as altruism, which can give the illusion of true empathy, and distinguishing the two can be tricky. The difference is that altruistic behaviors are often governed by a more selfish (though inconspicuous) incentive – the spread of one’s own genes.
To illustrate: while it might have appeared that this animal was genuinely concerned with the plight of a fellow tortoise, had we investigated the relationship of these two further, we might have discovered that the male tortoise had previously mated with this female and was thus exhibiting a simple, pre-programmed behavioral response to defend his genetic investment. (Consequently, some argue that this type of behavior, known as kin selection, does not represent “true” altruism, but it’s important to remember that the definition of biological altruism differs from the common usage of the term).
Of course, because we don’t know anything about the relationship of these tortoises this is all purely theoretical, but potentially altruistic behavior has been documented in desert tortoises before. Patterson (1971) reported that an overturned tortoise may give a call that elicits another tortoise to roll it back over. Check out this video that allegedly shows this behavior. (For another example of altruism in reptiles, see this amazing video).
All in all, my take away message here is that non-human animals are a lot more complex than we’ve been giving them credit for (and/or we’re not as amazing as we think). While new discoveries are being made each day, much is still unknown, and I think that’s pretty exciting.
Photo Credit: Zachary A. Cava