What did bats evolve from?
|Pipistrelle: The Tragus in the ears is easy to see here.|
Head: Bat heads often look a bit bizarre: The ears, which are noticeably large in relation to the head size - especially those of the "long ears" -, the small front button eyes, the grim mouth with the pointed teeth and finally the nose of the so aptly named "horseshoe bats" are all adaptations for insect hunting by echolocation:
- The big ones Ears must be able to pick up the echo of the ultrasonic calls and also be able to hear the slightest crawl of running insects. A vertical peg in front of the auricle, the so-called Tragus, apparently advantageously changes the incoming acoustic signal.
- The small eyes need not - like the big owl or cat eyes - be nocturnal; they are completely sufficient for spatial orientation during the day.
- The predatordenture is just right for insect prey and is shown so often to animal photographers because, apart from the "horseshoe bats", all bats have to open their mouths to locate ultrasound.
- The exceptionally shaped horseshoesnoses of the bat species of the same name finally enable their owners to call through the nostrils, i.e. with their mouths closed.
The question remains why some species have small ears and others larger ones. There are two reasons for this: Species that hunt crawling prey in the small air space of closed vegetation must have finer hearing and therefore larger ears than pure air hunters; and small bats among the hunters in the foliage probably have the same absolute ear size as larger species with the same hunting habits, because the same ear size relative to their body size would be absolutely too small to hear the little crawling.
Poor: Unlike birds, whose fingers have receded and are usually no longer visible from the outside, bats fly with their hands. Only the thumb has retained its original, short shape; the second finger consists of only one limb, the third one of three limbs, the fourth and fifth fingers each two limbs. The second and fifth metacarpal bones are greatly elongated, and the ulna (Ulna) has been lost so that the forearm is only a bone, the spoke (Radius) consists.
As with birds, the wing shape reveals the ability to fly: Long, narrow wings are characteristic of fast fliers in open terrain such as the noctule bat, which easily reaches 50 km / h, long, wide wings are typical for slow hunters, also in open air space and short, wide wings for the slower, more agile flyers in denser vegetation.
Legs: Typical for bats is hanging upside down: a quick start or a quick escape is only possible by dropping it. The so-called smooth-nosed bats (family Vespertilionidae) rest and keep their hibernation lying down because they move running and jumping and can also fly up with a short jump in the air; In the unprotected state of daytime sleep thargy, however, they are safer from predators hanging on a wall or ceiling than on the floor or in open crevices. The rarer horseshoe bats (Rhinolophidae) however, they are always helpless on the ground, as they cannot even lift their bodies and consequently cannot fly up; these bats are always found hanging.
Attaching to walls is made easier by the fact that the feet point backwards, not forwards as in other mammals. The claws of the feet are bent solely by the weight of the animal, so that it can get stuck in (winter) sleep and even in death. A bony spur protruding inward from the ankle towards the tail (Calcar) tightens the tail skin. Above the spur, the legs are usually included in the flight membrane, they stretch the tail flight membrane or fold it together.
Tail: With the exception of the bulldog bat, the tail of European bats is almost completely integrated into the flight membrane, which it stretches in flight.
Flying skin (Patagium): The double membrane between the shoulder, fingertips and tail is - apart from part of the tail membrane - hairless and very elastic and firm.
Hair: Bats do not have woolly hair, so only one type of hair. The person skilled in the art can recognize some genera and even species from the structure. The peritoneum is lighter than the back fur. The coat of young bats is usually darker and more dull than that of old bats. Color differences between males and females (Dichromatism) does not exist - unlike with birds.
Sexual characteristics: The mammary glands of female bats lie more laterally in the armpit area and are easy to recognize in mothers. The two-colored bat, however, has two pairs of teats and horseshoe bat bats also have a pair of adhesive teats on the lower abdomen.
In the males, the penis is always clearly visible because it is not withdrawn into the body, and in the mating season of some species also the testes and epididymis.
Familys: There are two groups of European bats: the "smooth-nosed" family and the "horseshoe bat". For an anatomical comparison, the "bulldog bat" is also listed here, which is only represented by one species in southern Europe. The following features are typical:
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