Sloth crosses road: insert joke here

May 18, 2011 • 1:51 pm

The poor beast can’t help it: the species evolved before there were roads!

The video describes this as “a sloth attempting to cross a busy road in Manuel Antonio, Costa Rica.”  This looks to me like the brown-throated sloth (Bradypus variegatus), of which I saw many during a summer in Costa Rica. Note the algae growing in its fur; one sloth expert describes its biological significance:

What I find most interesting about the three-toed sloth is the symbiotic relationship it has with other organisms. One effect of the sloth’s languid pace of life is that it can’t be bothered to groom itself. This turns out to be beneficial to several varieties of algae and mold that grow inside the sloth’s hollow hairs. The algae effectively turn the sloth green, giving it excellent camouflage among the leaves. The camouflage is crucial to the sloth’s survival, because its inability to move quickly makes it an easy target for the harpy eagle.

But the symbiosis doesn’t end there. The algae in the sloth’s fur provides food for a great many insects. (I should point out, incidentally, that sloths have extremely long fur, making them appear much larger than they really are.) Beetles have been found by the hundreds living on a single sloth. Another insect that calls the sloth home is a type of moth—Bradipodicola hahneli (or “sloth moth” to most people). The sloth’s fur provides both food and protection for the moth. Not only does it feed on the algae, but it also deposits its eggs in the sloth’s droppings, where they pupate and hatch, and then fly off to look for another sloth to live on.

h/t: Matthew Cobb

60 thoughts on “Sloth crosses road: insert joke here”

  1. I don’t know why, but I felt bad for the sloth. There’s no logical reason I should, any more than I would feel bad for a video of a human trying to climb a tree.

    2. It is a remarkable creature with the huge fore limbs & tiny rear legs! The guy who picks it up has clearly done so before as he seems wary of the claws. I am curious – are they always so easy to catch? Do they taste bad & is that why they have not been wiped out?

      1. …though another reason to not to believe in a creator god – it would surely be more convenient for the sloth to defecate while in a tree than descend to the ground onece a week!

        I see sloths are also coprophagous –
        doi:10.1016/j.mambio.2010.03.003

        1. just checking… You do know why it is proposed that they climb down to defecate?

          If not:

          If they defecated from the tree they are in, it would alert ground dwelling, tree-climbing predators where they are like waving a bright red flag.

          they climb down to defecate so they can do it away from the tree they are currently hanging most in.

          they aren’t like monkeys, that move from tree to tree quickly.

          You probably knew this already, but just in case.

  4. From the shadows of the cars at the beginning of the video, it looked like there was no one to stop traffic and that it was going to be a sloth snuff film. Thankfully the guy on the motorcycle came by and knew how to pick it up.

    1. I was worried too. I watched it first to make sure the sloth made it before showing to my daughter.

      Those short back legs are really strange.

    1. Ditto that! I sat there cringing the first half as every car went by saying “abunai! abunai!” (as if he could hear me telling him it was dangerous).
      I was struck by how clearly *well* adapted they are to living in trees by how pitiful they look on the ground.
      @Dominic– really long forelimbs! When they’re sitting in a tree, you don’t realize what a difference there is between the length of the forelimbs and the legs!

      Great video, Jerry–thanks! Will be showing this one to the kids since we (coincidentally) *just* watched a whole program about sloths on Animal Planet last weekend (where they went into the algae turning the hair green, the insects living off the algae, and so on). Sloths turned out to be much more interesting than ever I knew!

    1. I looks a bit like me yesterday at the end of the 5 k race I participated in. (Trying to beat my own best time by running FAST the first three km.s – Stoopid)
      Sorry I laughed at you earlier, sloth. You could have had a good reciprocal laugh at me yesterday.

  7. Is it just me, or does Motorbike Man’s sudden appearance remind you of Batman arriving in the nick of time to save the day?

    1. It seemed to me like the scooter guy might have been wearing some kind of uniform?

      maybe some kind of park ranger type?

      1. on second though, he might just be dressed to stay alive on the roads there (reflective vest, light shirt, etc.)

        1. Sadly his protective clothing didn’t extend to trousers, gloves or a helmet.

    1. That is a key question. If there is no benefit to the sloth, then this is not symbiotic and could not be due to natural selection on the part of the sloth.

      1. no, it is a form of symbiosis, it just might be of benefit to one party.

        mutualism: Both host and symbiont benefit

        commensalism: symbiont benefits, little or no host benefit

        parasitism: symbiont benefits to detriment of host

        Ammensalism: neither benefits, one is harmed.

      2. jay, don’t know your age, but these definitions underwent a shuffle sometime after I left academia…sigh.

        1. these terms get more rigidly defined as we find more and more examples of each.

          I’ve seen modern bio curricula that still only include two, most commonly 3, and typically ammensalism is left off because of confusion as to whether it really represents a symbiotic relationship or not (it does).

          I think the basic terms were pretty well defined by the time I made it to grad school in the late 80’s, if not a bit sooner, but I can imagine a great deal of people not really being exposed to them unless they took a specific uni-level course in ecology or animal behavior.

          1. I dropped out of grad school in ’72…Previously had been exposed to the terms rather a lot–did some undergraduate work on lichens.

          2. lichens are really interesting, IMO.

            It’s been one of the notable things I’ve been observing on my treks around NZ; with all the moisture here, you get ones that are just as interesting growing on buildings in the cities as you do miles away in the middle of nowhere.

            A quite common one tends to coat rocks and buildings with a bright orange carpet.

  10. The other people were just going to watch it get run over?

    I rescued a turtle off a busy road yesterday. I guess famously slow animals crossing the road is the theme of my week.

    I’ll be on the look out for a snail..

    1. Well at 0:18 they do say they’ll block traffic when the sloth actually gets to the road.

  11. Inter-species altruism, Dr Coyne. And how do you explain that?!!! Or will you leave it to David Brooks…

    1. To say that inter-species altruism doesnt make sense implies that the altruism response should be perfectly fine-tuned. Why should we expect it to be?

      Other evolutionarily programmed responses are frequently triggered by things that prove the response can be “tricked”. Feeling that a doll or teddy bear is “cute” is one example.

      Ive seen video of a light bulb or billiard ball placed near the nest of a duck sitting on eggs. The duck rolls the foreign object into the nest with the rest of the eggs.

      The response doesnt have to be perfect with regard to what triggers it to increase reproductive success.

    2. I think that interspecies altruism is likely an artifact. Our altruism has not been ‘intelligently designed’ so that it fits one purpose, it’s a pattern of behavior to help other appealing looking (appealing in the sympathetic, not necessarily the beauty sense). The fact that it sometimes spills over to help members of other species is incidental.

      Note too that there is little evolutionary cost to this type of action so little to select against it. The human was at very little risk to himeslf… had the sloth been crossing by a mountain lion, I doubt the human would have been so helpful.

      1. Thanks, Ralf. I think you’re the only one who realised that my comment was intended as a joke.

  12. Here’s one for Ben…

    Q: what’s the difference between a dead sloth in the middle of the road and a dead trombonist in the middle of the road?

    A: the sloth might have been on his way to a gig.

  13. I think I read that sloths are the most abundant mammal in the jungle. I recall reading a note in BioTropica about two male sloths having a territorial dispute. The sloths were moving much faster than usual, and their speeds were given in sloth lengths per minute. I’ve only seen one sloth in the wild, but then I don’t spend much time looking up in trees.

    1. years ago I read an article (couldn’t remember where now) contrasting the sloth and the armadillo which evolved in the same environment.

      The sloth became highly specialized to the jungle environment, so while successful there, spread very little. The armadillo developed a more general strategy and spread widely outside the jungle where it evolved.

  14. Q: Why did the sloth cross the road?

    A: He wanted to try life in the fast lane.

  15. Am I the only one thinking that the sloth at the end going WTF I didn’t know I could fly! Weeeee

  16. > The poor beast can’t help it: the
    > species evolved before there were
    > roads!

    Well maybe, but I suspect Megatheria would have had less of a problem with crossing them.

    2. AFAIK Megatherium (hypothetically) ate Glyptodons, which look like cars. If the floor of modern is thin enough, it might even find something to eat.

  17. The christian will now need to forgo their worship of crossed death sticks. The video is clearly a message from one or several of the christian gods; the jebus was saved on Its way to the nail appointment, not during and not after. Also, the message is again clear as per usual, the jebus was treated with reverance prior to the appointment as It was picked up by Its scruff and flown first class to within feet of Its destination.

  18. I was really puzzled by the way the guy picked up the sloth, because it didn’t match what physics requires would happen with a one-handed pickup of something that big. Then I read the bit about their fur being very long, obscuring their true size.

    I love learning interesting tidbits like that out of the blue.

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