Why Don’t Sleeping Bats Fall Down?


♪ Intro ♪ Let’s say I just really wanted to sleep in a tree tonight but I forgot to bring a hammock. If I wanted to get more in touch with my animal side, I could make like an orangutan and build a nest out of branches and leaves, or copy the koala and wedge my butt into a joint or crevice and hope for the best. One mammal I’d better not take inspiration from is the bat. I can barely hang with my arms for more than a minute, so I don’t think my feet are up to the job! But bats! Bats can hang upside-down for hours while they snooze because of a special mechanism in their feet. They don’t have super strong gripping muscles or anything. Active clenching in any mammal quickly fatigues muscles, and bats simply don’t have that kind of energy to spare. They have flying to do! Besides, muscles tend to relax during sleep, something you’ve probably noticed if you’ve ever woken up with that book you were reading flat on your face. The bat’s secret is not to use muscles at all while they hang. Instead, they’ve evolved a nifty mechanical trick with their tendons. Generally speaking, the job of a tendon is to connect muscle to bone, but bats have another use for them. Special tendons connect their legs and feet to their upper body and are pulled tight by the bat’s weight as it hangs. Like most tendons, they’re surrounded by a smooth, slippery coating called a tendon sheath that keeps everything sliding along nicely. What’s special about these tendons is that they have rough bumps like saw-teeth on the outer side. They face the sheath, which has ribbing on part of the inside that neatly fits the size and shape of the spaces between the bumps. When a bat finds a good spot to hang out and grabs on with its feet, the tendon pulls down and the saw-teeth slide along the ribbings like a ratchet, holding the feet clenched. The bumps on the tendons are angled so that once the ribbings slide in, they lock in place. This takes almost no effort from the bat, so it’s called a “passive digital lock.” The bat can sleep soundly without tiring itself out or falling to the ground. It’s so passive that even dead bats have been known to be hanging. Their grips are so tight that smaller bat species can cling on to even the tiniest ridge on a cave ceiling. Birds might have a similar locking mechanism to keep them perched on top of branches, but scientists still aren’t sure how they use it. And certain mice use a system like this to help them climb. Not all bats can do this, though. Vampire bats, for instance, don’t, but they do have much stronger legs. They eat on the ground or from the backs of their victims, so they need to stay quick and agile on their feet. So what’s the advantage for those bats that do hang? Well, for one thing, you don’t find too many predators on the underside of branches or the roof of a cave. Plus, taking off is also a whole lot easier if you can just release your feet, open your wings and soar. No energy-wasting run-ups needed. As long as you won’t fall to your death, sleeping upside-down sounds kinda fun. Thanks for asking, and thanks to all of our patrons on Patreon who keep these answers coming. If you’d like to submit questions to be answered, or get these quick questions a few days before everyone else, go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe! ♪ Outro ♪

100 thoughts on “Why Don’t Sleeping Bats Fall Down?

  1. So, I've been wondering about this for a while?

    If bats hang upside down when they sleep, does the poop land on their face or back?

  2. What a great question and what an interesting answer. I gotta say it's something I never thought to even ask before.

  3. How do they un-ratchet them? I imagine a deliberate physical action is required, obviously not something that can happen by accident, but what's the "release mechanism"?

  4. I'm sorry, but did Michael just say, "and thanks for all the Patreon supporters who keep the answers coming." Isn't suppose to be these question coming? Just a thought

  5. And now for the follow-up question – how do bats avoid having all the blood rush to their heads while sleeping upside down? Special heart-pumping mechanism? Capillary action? Tell us!

  6. I still don't understand why clenching our fist makes our muscle sore, when our muscle's natural resting state is contracting.

  7. Why do my ears get itchy?

    It occurs mostly when I have the cold and I makes me want to pull my hair off to make it stop.

    Of course I am asking about that itch that makes no sense to be there- no ear wax, no foreign object (like a bug- yuck) just a tingling sensation deep inside the ear

  8. hi Scishow, im laying in bed with a serious cold or whatever…and i was wondering…
    why is it called a cold, if our body temperature rises?
    and is it true,if youre in a cold room, you can catch a cold? like whats the dealioo…isnt it from bacteria?

  9. If you ask common people they will say bats drink blood, but in reality there are more than a thousand bat species and only vampire bats do that.

  10. Just a lil notice to ppl who gets bats inside They wont wake up if the light is on turn it off so they can go outside and nomnom on them pesky bugs 🙂 Backstory: I tend to get quite a few bats inside during summer they usually lie flat against the wall rarely on roof (probably just surface difference) but if i don't make it dark they just hang there several days after 2 days i realize this and shut of computer and other light sources as sun went down happy bat flapped off and never returned. this is one of many cases but i learned first time to make sure they can get darkness to flappity flap away

  11. I wonder it they have a cardiovascular system to prevent blood pooling in their heads while they sleep. It could be a non issue with an animal this size though.

  12. do bats feel uncomfortable when sleeping next to each other, & do they have the same muscle protein that keeps them from acting out in their sleep just like us humans/mammals?

  13. So how does their blood stay pumping regularly throughout their bodies when hanging upside down instead of rushing to their heads and upper body?

  14. so.. how often do they fall to their death while sleeping? And wouldn't the blood go to their brain? how do they deal with that?

  15. Still people don't care about them because they are vulnerable to the white nose syndrome, pollution, insecticide, disturbance (the crew of expendable 2 killed around 20 000 bats)

  16. How do bats not die from the intense blood rush to their heads? A human hanging upside-down would pass out and die after a while.

  17. Actually the question they didn't address is: Does the blood go to their heads as it would us and why don't they have this problem? Size of the little critters I assume.

  18. I think you could theoretically build a bat suit with this idea that could support a human hanging upside down. Like if it had support strings to keep your feet at a 90 degree angle in special bat-like shoes, and the strings could go all around your body within the suit to support the pull. Could it be done?

  19. QQ: Why do some homosexual men develop an accent which makes everyone aware of their sexual preferences? Just what about being homosexual and a man makes some people sound like they do with an accent which no other demographic appears to have?

  20. QUESTION FOR YOU: why when we stay upside down we feel the blood going to the head, but when we stand up we don't feel the blood going to the toes?

  21. Doesn't the blood being pulled down by gravity mess with their head's or something, it's weird that they would find it comfortable.

  22. I believe as human if we hang upside down too long, high blood pressure would form in our head, and if the blood vessel were to burst, STROKE

  23. So how long until us climbers can get proper blood control when upside down and ratcheting tendons for our hands? I have been waiting for that upgrade to come out for almost a few years now it feels like.

  24. I heard sloths have something similar. It helps protect from human hunters since even if they are shot they stay hanging in the tree.

  25. 2:15 why is my next thought 'yeah, hanging in a cocoon before you die' like it's a natural addition. WTF of morbid mind of mine?

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