• Question: how can crokodiles hold there breath under the water for up to 45 minutes

    Asked by to Andrei, Ekbal, Gemma, Helen, Ruth on 24 Jun 2014. This question was also asked by .
    • Photo: Ekbal Hussain

      Ekbal Hussain answered on 24 Jun 2014:

      Hi Renniec,

      Another excellent question. I don’t know much about this but I’ll try and answer your question.

      Crocodiles, being reptiles, are cold blooded. So they need a lot less energy. Underwater the crocodiles don’t usually move much. And so they use a lot less oxygen. Moving muscles use up a lot more oxygen than ones that don’t move. It works for people too, you can generally hold your breathe underwater for longer if you don’t move.

      So crocodiles don’t actually do anything special. They just hold their breath for longer by not moving much.

      Hope that answers your question.
      Ekbal

    • Photo: Helen Gath

      Helen Gath answered on 25 Jun 2014:

      Hi Rennie, I really like your question, and even though Ekbal gave a great answer I was very curious to read about it myself. In doing so, I found a few extra facts I though I would share.

      I shall try and summarise it as simply as possible;

      * Humans have two blood circulatory systems in the body. One for freshly oxygenated blood, collected from the lungs and distributed around the body. The second carries de-oxygenated (low in oxygen) blood which the body has been used. It collects ‘used blood’ and returns it to the lungs for a ‘re-fill’ of oxygen.
      *Crocodiles don’t do this. They have a mixed circulatory system; oxygenated and de-oxygenated blood travel together in the same channels.
      * Why is this important? Well if the croc is underwater it can’t use its lungs – it doesn’t breathe. This means there is little point pumping blood via the lungs to collect O2, so the bloodstream is diverted away. Even though it’s oxygen poor, a little bit more use can be made out of it…’squeeze the last drops’ so to speak!. All about prioritization. The heart actually closes ceraitn valves (a bit like closing a door) slightly to restrict blood flow to the lungs. It does this in response to the nostrils being closed off when submerged.

      * Another way they can get the most out of the oxygen left over in the body is to change the chemical reaction process. Usually our cells respire aerobically to produce energy. Nut they can also respire anaerobically when there is limited oxygen supply. This method is not as efficient, a bit like you using your left hand if you’re naturally right handed, but you still get the job done.

      * Overall, crocodilians slow their metabolism right down so they expend little energy, and therefore don’t need as much fresh oxygen as normal.

      Hope you found that interesting and not too complicated 🙂

Comments

  • Photo: Thon

    Thon commented on :

    Greetings from the Animal Behaviour Zone. ^_^

    Ekbal is pretty much on the ball, here. When underwater, crocodiles are pretty sedentary (they don’t move much), which helps them save oxygen. In a similar way, deep-diving mammals prefer to sink, rather than swim down. The more you move, the more oxygen you use, and the less time you have underwater.

    While cold-blooded animals can get into pretty serious trouble if they get too cold, crocodiles are pretty resilient. If they’re in serious trouble, they can allow their temperature to drop by quite a lot, giving them far more time underwater.

    But crocodiles DO have something special about them too. When staying underwater for long periods, their blood supply starts shutting down to non-essential areas. Kind of like ours does when we get too cold. Even better for the crocs, their blood is great with oxygen, taking it up quickly, holding on to it, and then releasing it really quickly where it’s needed.