they like the headrush
Their body are adopted to cling upside down.
Because they can.
they sleep upside down beacuse yhey feel safer like that
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Why do bats sleep upside down?
Because they need to put their feet up. Since bats are the only mammals who can fly, with wingspans ranging from 6" to 6', they failed to make great strides in the walking-about, or in the standing departments. Their legs and feet are simply not strong enough to support these functions for great lengths of time. For this very reason, bats, when in their bat caves, or roosting in trees, take the weight off of their tired limbs by hanging upside down. Their breast-feeding babes, born live, as are all mammal offspring, have no choice but to hang in limbo with mom. Together, they reap the benefits of downward gravitational pull. Bats also invert our common beliefs regarding their eyesight. The bat, a nocturnal creature, hunts its prey at night, and rests up (or down, as is the case) for the evening's events by day. One would be incorrect in assuming that the bat has keen night vision, to assist it in its feeding frenzy. Not so. The bat employs an echo system, whereby it tosses out a high-frequency sound, one inaubible to the human ear, which in turn strikes a target, and then bounces back to the bat, thereby letting it know what lies ahead. Were it not for the bat's radar, we would hear even more bumps in the night than we already do.
Bats hang upside down all the time except when they urinate and
defecate. To the question why they hang upside down?
An simple answer is that they have evolved in that way. Hanging upside
down is advantageous to them that why that behavior is retained in
the course of evolution. Then 'What are the advantages of haning
There are two main advantages.
1. Bats are nocturnal animals. They go in search of food during the
night time. Their night time activity protects them from many of the
day active predators. In the night, bats have to protect themselves
only from a limited number of night active predators (like cats,
snakes, owls, night jars etc). A simple and best way to stay in the
ceiling. The best way to stay in the ceiling is to cling on to the
roof of the ceilings. where bats can not be reached easily by their
2. The food resources for them are limited. From what ever little
food they get they have to efficiently budget their total energy for
maintaining their basal metabolism, flying, reprodution etc. Birds
being powerful fliers, have well developed chest and wing muscles and
spend more energy to take off from the ground - against the
Bats avoid spending most of their energy for the taking off by hanging
upside down in high raised ceilings. As they drop down from the
ceiling they start flying. This could be an "intelligent" adaptive
strategy to conserve energy. Instead of taking off from the ground
level (which needs lots of energy to lift the body against the
gravity) "evolution" has tried a different strategy in bats - to live
hanging upside down (to conserve energy)!
From a wildlife bioligist colleague:
"They need to drop into flight so this position sets them up for that.
Their feet are designed to grab and hold but their forelimbs are wings and
have very little holding capacity. The feet work so well at holding on that
a bat can die and will remain hanging by its feet.
...because the forelimbs are adapted for flight the back limbs have to carry
the load during rest. Gravity being the way it is, hanging by the feet is
the only option. Using the thumb claws they can climb effectively and
maneuver while not flying but the thumbs can't hold the full body weight for
any length of time without the feet helping."
Bats always sleep upside down hanging from a high and secluded spot. The biological characteristics of bats make it necessary for them to sleep in this fashion. Bats cannot launch themselves into flight from the ground, like birds do. This is because their wings are not as powerful as that of the birds and they cannot produce the necessary lift for starting a flight. The hind legs of bats are also not strong or developed making it possible for them to run and gain the momentum for flight.
Hanging upside down gives bats an ideal position to take off into a flight when necessary. They can just let go and on their fall through the air they will get the necessary momentum for taking off into flight.
Hanging upside down also hides the bats from predators. Besides, they don't have to exert any energy to hang upside down because of the unique way their talons are formed. It is just their weight on the talons that keep it closed around the surface where they are locked. As long as the bats are relaxing in this position, the talons cannot open and the bats will not fall off.