In honor of Halloween this month, QUEST offers up a short story on bats. But these are not your screeching, swarming, bloodsucking Hollywood movie bats. No... just like you can choose to make a cute, happy jack-o-lantern or a scary jack-o-lantern, you can also choose to do a story about cute fruit-eating bats instead of their less attractive cousins.
So we visited zookeeper Andrea Dougall at the Oakland Zoo to learn about their Malayan and Island Flying Fox. Both are a type of fruit bat, and I couldn’t readily see the difference between them. There are many fascinating things that Andrea taught us about these bats that we couldn't fit into our two minute segment (and honestly, this producer wouldn't mind making a half hour special on these critters!). For instance, they have a lot of blood vessels in their wing tissue, so they make excellent thermo-regulators. If the bat is cold, he wraps himself up in his wings so that the heat from his blood vessels can keep him warm. Likewise, when it's hot out the bats flap their wings to cool off.
When Andrea told us that bats are the only mammals that can have sustained flight by flapping their wings, someone said "but what about the flying squirrel?" Nope-- they glide.
These bats don't actually swallow the fruit that they eat, instead they chew it into small pieces, push it up against the roof of their mouth to ring out the juice, which they then swallow, and spit out the leftovers. This is something that Andrea reminded me of when I told her I'd like to take one of these cute critters home as a pet... the amount of rotten fruit pulp that you have to pick up is really unappealing. Plus, of course, it would be illegal.
Perhaps the most intriguing thing to me is the simple fact that these animals spend all of their time hanging upside down. I asked Andrea about that too-- how is it possible that they wouldn't experience some sort of leg fatigue and let go of their grip? She told me what's in the scientific literature on other kinds of bats (and we're assuming it applies to fruit bats as well). The deal is that the tendon of the muscle that flexes the claw passes through a tough sheath that consists of 19-50 rings, oriented at an angle so that the inside surface is ridged. So there's some ratchet-action going on in the sheath that holds the claw in a grasping position even after the muscle has relaxed, and it's the tension on that tendon from the body weight that holds the ratchet in place. When the bat wants to move, the tension is released and therefore the claw releases its hold. So basically, the clenched position is the "at rest" position, and the releasing of the foot is the part that takes energy.