Bats are the only mammals that possess true, flapping wings and the ability to fly (as opposed colugos, for example, which glide). Bats’ wing membrane (the patagium), an extension of the skin of the back and belly, provides a high degree of manoeuvrability in flight. Bat Animal Wingspans range from over 1.5m (5ft) in the large flying fox to as little as 15cm (6in) in the hog-nosed bat.
Over half the species echolocate (see below) to capture prey and to navigate at night. Bat Animal Chiroptera is a huge order that comprises nearly a quarter of all mammal species and is exceeded only by rodents in and temperate terms of species numbers.
Bats are common in tropical are too cold to habitats worldwide but are not found in environments that are too cold to support a source of food, such as the polar regions.
Perhaps the most distinctive feature of bats is their wings, which are formed from a double layer of skin stretched between the side of the body and the 4 elongated fingers on each hand. Blood vessels and nerves run between these 2 layers.
Extra support is required for the arms to be used as wings, and this is provided by features such as fused vertebrae, flattened ribs, and a strong collarbone. The sternum (breastbone) has a central ridge to which the large muscles used in the downward stroke of the wing are attached.
A short, clawed thumb is present in most species at the point where the fingers join, and a cartilaginous spur (the calcar) on the inside of the ankle joint assists in spreading the tail membrane.
Bat Animal All microchiropterans echolocate. When used in flight, this navigation system makes them formidable hunters. Sounds (“clicks” are produced in the larynx, emitted through the nose or mouth, and directed or focused by the nose leaf (if present).
Once the clicks have reflected off an object, the returning echo is picked up via the bat’s sensitive ears. The time it takes to receive the echo reveals the size and location of anything in the bat’s path.
USING SOUND TO FIND PREY
Bat Animal of the insect-eating bats use echolocation to find airborne prey. When searching for food, such as mosquitoes and moths, the bat emits a series of clicks, Bat Animal represented by red bars on this diagram. As the bat approaches its prey the time between “clicks” shortens. This helps the bat to pinpoint its target.
EQUIPPED FOR ECHOLOCATION
Bat Animal Although bats’ eyes are well developed, hearing and the sense of smell are more important than sight. Many microchiropterans, such as this neotropical fruit bat, also have a large nose leaf which assists echolocation.
The function of the tragus (a lobe in the front of the ear) is uncertain; it may improve the accuracy of echolocation. Megachiropteran bats generally do not echolocate and have larger eyes (for detecting prey) and smaller ears.
FEEDING ON FRUIT
Bat Animal Most fruit-eating bats use their senses of sight and smell to find food and so lack facial ornaments used in echolocation. This epauletted fruit bat is eating a mango; a group of these bats in a plantation can cause considerable damage.
As fruit bats require a constant supply of ripe fruit, they are found mostly in tropical areas. Fruit bats often feed in groups and fly long distances in search of food.
Foraging and diet
Many bats eat insects: some species forage for them among shrubs and trees, while others skim the surface of the forest canopy to catch higher- flying insects. A single bat may eat hundreds of mosquitoes in one night (thereby lessening the incidence of malaria in other animals).
Other bats eat fruit, and some use their long tongue to feed on pollen and nectar. Vampire bats use their sharp teeth to make a small incision in the skin of an animal while it sleeps and then drink the blood. Carnivorous bats prey on lizards and frogs, fish-eating bats use the hooked claws on their powerful feet to capture fish (see below).
FEEDING ON BLOOD
Vampire bats are well adapted to feed on blood. They have sharp incisors to cut into flesh, and produce saliva that prevents the R blood from clotting. This white winged vampire bat commonly feeds on the blood of chickens.
Bats often gather in great numbers at a single site, which may be a cave, the roof of an old building, or a hollow tree. All roosting sites must provide a resting place that offers protection from predators, the heat of the sun, the low temperatures of winter (hibernating roosts), and rain.
Bamboo bats are small enough to roost in the hollow stems of a plant, while some species of leaf-nosed bats bite into leaf stems so that the leaf droops downwards, forming a tent around them.
Why bats gather in such large numbers is not fully understood; however, at the end of hibernation, bats living in colonies often weigh more than species that do not.
Bats, the only mammals that can fly, have structural adaptations that allow them to make up-and-down movements of their wings (n the same way as birds). The open wings of this New World leaf-nosed bat reveal the extent of the wing membranes.
A PLACE TO REST
Bats, such as these fruit bats, commonly roost in caves during the day, emerging at dusk to feed. Some species use the same roost for many years and gather in groups of many thousads.
Despite being rich in terms of species, bats face a huge variety of threats. Globally, one of the most serious is habitat loss, particularly in forested regions. Fruit-eating bats are also persecuted as pests, and are killed by colliding with power lines, while insect-eating bats are threatened by white nose disease-a potentially deadly fungal pathogen that first came to light in North America in 2006.
Bats are now routinely fitted with microchips and radio collars that allow them to be tracked. This fruit bat (below) will broadcast for several months, showing exactly where it roosts and feeds.
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