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Animals evolve to play?

January 15, 2012

So this Russian home video of a crow appearing to sled down a roof has gone viral. Animals at play are well known–especially baby animals, which behaviorists hasten to say are “learning” skills. What puzzles me is why a warm-blooded adult animal in the harsh Russian winter, who needs food and shelter, would spend time sledding down a roof? And push at the end, to make the ride last longer?

Maybe evolution actually produces animals that play, either because play behaviors enhance survival somehow (stranger connections have been shown); or else because (a more dangerous guess) play is an inevitable “byproduct” of selected behaviors, not an adaptation itself.  Maybe that also explains why this deer splashes in the puddle. Animal biologist Bruce Bagemihl takes this argument a step farther, in Biological Exuberance, where he explores the diversity of animal sexual behaviors. He argues that most sexual behaviors, especially in mammals, have no direct consequence for reproduction but are actually forms of play–for instance, dolphins that buzz each other’s organs with sonar. So how much of animal behavior is just “play,” or what Bagemihl calls biological exuberance?

Here the biologist must be skeptical that any trait evolves without positive selection (i.e., if you lack the trait you leave fewer offspring.)  Some counter arguments:

–The crow isn’t really sledding. It’s just trying to keep its footing while pecking food out of the jar lid. And the deer is just exercising its limbs, the cervine equivalent of pilates.

–The crow and deer are playing, but these behaviors evolved to showcase their health–to act as “honest mating signals.” Animals that can sustain excessive behaviors and/or body parts (such as a peacock’s tail) advertise their genetic health.

–The crow and deer are playing by “mistake.”  All animals make mistakes–otherwise, predators would go  hungry.

What do you think? Is the crow playing? If so why?  Other examples?

  1. January 16, 2012 12:54 am

    Playing makes excellent sense; the trait is particularly valuable for learning when young, and persists because it doesn’t have a high enough cost to be selected against. I like the theory that adult play is a sign of fitness— that the being is sufficiently successful that it doesn’t have to spend all of its resources on survival.

  2. January 16, 2012 9:22 am

    The problem with the “honest mating signals” and “mistake” arguments is that it draws a line between animals and people. At some point, the “fun” behaviors became culture, and that’s a slow-moving spectrum. It’s just like the other human-centric items such as language and tool use: We’re not the only ones, we’re just the best at it.

    Every dog I have had has been able to entertain herself, and there’s no mating benefit in there (my previous dog would take a tennis ball up stairs just to drop it and chase it). This case is merely novel because we think of birds as stupid (birdbrains, for example), yet corvids, pigeons and parrots are quite bright.

    My theory is this: brains have pleasure centers wired to ensure important things like eating and mating get done. Those pleasure centers can get tweaked by other non-productive things (drugs such as alcohol — animals get drunk too, surviving a cheap thrill like sledding, etc.). Humans are just the only ones who have enough economic surplus to spend a large portion of their entire lives on this.

    • January 16, 2012 10:01 am

      I like your point about “mistake” and “culture.” It could be argued that human culture in its extreme actually detracts from biological reproduction; in effect, the machines become our children.

      With nonhuman animals, an argument is that dogs and other domestic animals have undergone selection for their human-favored tendencies, and that adult playfulness could be part of it. With that in mind, the behavior of animals in the wild gets more interesting.

  3. Marked One permalink
    January 16, 2012 1:31 pm

    Looks to me more like it’s scraping it along the roof and then pecking some food of some type from the under(side). Crows are super smart creatures, so it’s probably not for us to overlay our thoughts of ‘play’ onto them.

  4. January 16, 2012 2:36 pm

    I can remember running across a field just because it felt good, also skipping, spinning til I got dizzy, and climbing trees. I think exuberance exists separately from reproductive behavior, or at least has some subconscious, non-linear connections with it. The activities I naturally enjoyed always seemed like worthwhile activities at the time. Perhaps ‘play’ is a neutral gear we go into when survival and security have been momentarily satisfied–a way of remaining ourselves even when we are not struggling to stay alive.
    The urge to be busy about something is a vital survival trait–‘play’ may be the off-switch we use when our metabolisms have excess vitality and an empty to-do list.

  5. SFreader permalink
    January 16, 2012 2:37 pm

    Some traits are selection-neutral and get passed along for as long as they don’t negatively impact survival.

    Crows are considered pretty intelligent: curious – peck/drop things to test them; highly social; and, use tools. The sledding activity in this video could be attributed any of these reasons. Would be interesting to see a follow-up video to see what the actual motivation was and see whether this bird invited other crows to try a new gadget, carried the lid off somewhere, or returned to ‘sled’ again.

    The deer splashing video suggests that playing around helps young animals face and conquer potential threats – in this case, water.

  6. January 16, 2012 3:20 pm

    Joan, why do you say that the byproduct theory is a more “dangerous” guess? In what way(s) is it more dangerous? Less likely to be true, or negative consequences…?

    (Also, aside: I would love it if you added a google +1 button to your posts.)

    • January 16, 2012 5:32 pm

      By “dangerous” I meant, intellectually dangerous; that is, likely to lead down a blind path. Too often we find that aspects of living organisms that seem to be there at random actually have selective significance. Even when something starts out random, like an animal appears a different coat color, surrounding organisms will adapt. A good example is human intestinal bacteria. These were long thought to be a random collection of “commensals” that just hang on for a free meal. In fact, we increasingly recognize gut bacteria to be a functional part of the human body.

      I would add the Google+ button, if there is a widget in WordPress; I don’t yet edit the code.

      • January 19, 2012 1:26 pm

        Thanks, that’s a good point.

        It seems to me that play would likely confer a survival advantage, by leading to novel behaviors some of which would turn out to be beneficial. Other novel behaviors might turn out to lead to a “Darwin Award” consolation prize, but overall I suspect playful species would benefit.

        I encountered a similar idea in a little book I read a decade ago called “Animals and Psychedelics: The Natural World and the Instinct to Alter Consciousness” by Giorgio Samorini, which gave a lot of entertaining examples of drug-taking behavior in the animal world. The author argued that “beings who consume psychedelics–whether humans or animals–contribute to the evolution of their species by creating entirely new patterns of behavior that eventually will be adopted by other members of that species.”

        The same argument can be made about playfulness in general.

        • January 19, 2012 1:35 pm

          For non-indented reply, see below.

  7. January 16, 2012 10:08 pm

    Coincidentally, I wrote about this a bit today.

    • January 16, 2012 10:43 pm

      Very cool pix! Chuq, what surprises us is not the intelligence (crows can count numbers better than some people) but that this one seems to use it for play, instead of something like getting food. Enjoying uncontrolled sliding downhill is a pretty sophisticated taste, IMHO. (I admit I gave up skiing years ago.) Is play an automatic consequence of intelligence?

  8. January 17, 2012 8:03 pm

    I’ve seen that “oh cool, that was fun!” look on a pet pigeon I had once. Crows aren’t alone in inventing games.

    The woods near my place are pretty dense, and mountain bikers have carved tunnel-like paths through them. There’s a Cooper’s hawk that lives in the area, and according to the bikers, he will go flapping up the tunnels ahead of the bikers for quite a ways.

    He’s only done it with me once, because I walk. Now, when I see him, he gives me a disgusted look and flies away from the path at a right angle every time he sees me.

    Guess I’m not fun enough.

    The thing I’m having trouble with here is the assumption that winter is a hard time to be a crow. With all that trash and carrion around? Why would it be hard? Similarly, the hawk who likes being chased by cyclists doesn’t look scrawny, and my pet pigeon certainly lacked for nothing.

    If life’s easy for the moment, why not do something that feels good? It keeps you sane and healthy, whatever your species. I’m not a huge fan of Bagemihl’s exuberance hypothesis, but I do think that we biologists too often assume that nature is always on the edge, a “World of Survival” as the old TV show had it. There’s no particular reason to assume this is true, at least without evidence.

    • January 17, 2012 9:56 pm

      If “it keeps you sane and healthy” then it contributes to selective fitness, right? 🙂
      Among humans, too, resource limitation does not eliminate play, outside of extreme starvation.

    • January 18, 2012 3:53 pm

      Mmm cookies… hunh? What were you saying about sane and healthy? Chocolate contributes to health, if it’s dark, and…Yeah, right.

      Probably feeling good and staying sane and healthy aren’t necessarily mutually overlapping, despite what I noted above. For example, the best thing I could do for my health right now would be to eat less, blog less, and exercise more. Besides, the type of exercise recommended tends to be boring as heck (is that because it’s good for you, or because high repetition exercises are easy to quantify in studies? Hmmm). But if I did all that, I wouldn’t be writing this response now, would I?

      The bigger point is that the crow doesn’t appear to be in survival mode, so assuming that its actions are tied to its fitness in any measurable way is extremely problematic. Most organisms don’t get a Darwin Moment every day. Heck, many Americans get through life with only a handful of opportunities to select themselves out of the gene pool. Why assume that what we’re doing right now has any effect on our fitness one way or another, especially if we’re post reproductive?

      • January 18, 2012 5:26 pm

        Heteromeles, what you need is to get retinal laser glasses so you can blog while running a marathon. 🙂 Actually, I highly recommend running; I run an hour most days, and find my brain writes best then.

        Americans “select themselves out of the gene pool” by having fewer children than replacement rate–because our high-tech culture and “interesting jobs” are too distracting. That is what I mean by the parasitic nature of modern culture. If it weren’t for immigrants, Americans would be going extinct–like the Japanese. And to a lesser extent the Italians, Spaniards and Russians.

  9. January 19, 2012 1:43 pm

    Arthur: “entertaining examples of drug-taking behavior in the animal world.”

    Actually, there are other hypotheses for evolution of psychedelics–from the point of view of the plants that make them. Plants often have two aims with respect to animals: (1) get their fruit eaten, to spread their seeds; and (2) stop the animals eating their leaves. To encourage fruit consumption, the fruits are sugar-loaded and colorful. Leaves, OTH, are dark green–and full of psychedelics.

    Why psychedelics but not poison? A lethal poison would kill the animal, and keep it from spreading the seeds. Psychedelic, on the other hand, just gives the animal a scare (monkey falls from tree) and reminds it to avoid eating leaves next time.

    But plants didn’t reckon with highly intelligent animals like primates and parrots who might find the experience rewarding, so they have to put up with a certain amount of grazing.

    • January 19, 2012 2:19 pm

      Personally, I think producing alkaloids for primates is a highly rewarding procedure. Tobacco, coffee, and tea (not to mention coca) have made very good niches for themselves attempting to poison us and failing. This was true even before industrial agriculture got hold of them.

      The other big point about alkaloids (to pick on that one group) is that they contain nitrogen, which means they are resource intensive to make. All the nitrogen a plant puts into alkaloids is nitrogen it can’t put into proteins, so too much alkaloid production hinders growth. As a result, one would expect plants to put out just enough alkaloids to minimize harmful browsing, without destroying their ability to compete for light and nutrients with other plants. You can taste this on islands with few herbivores: the plants that grow on islands tend to be sweeter and less aromatic than those on the nearby mainland, so long as the island is largely herbivore free. They also tend to grow bigger and faster, meaning they invest more in growth. However, introduce an herbivore, and island plants really suffer.

    • January 20, 2012 1:23 pm

      Joan, that’s an interesting plants-eye-view of the situation. I was looking at it from the other side: once it got started (by whatever means), could it have beneficial effects for the species that consume them?

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