WHAT ARE BATS?
As freaky looking as they are, bats are mammals - like us! They are often mistakenly called 'flying rodents' or 'flying rats', but despite their obvious, superficial similarities they are not directly related to rodents, and much less to birds, and strangely do not have any closely related orders. Furthermore, their uniqueness can be demonstrated by the fact their closest living genetic relatives are thought to be carnivorans, certain hoofed animals, such as alpacas and hippopotamuses, and sea mammals, such as dolphins!
Bats do not flap their entire forelimbs, as birds do, but instead flap their spread-out digits, which are very long and covered with a thin membrane or patagium.
Bats represent about 20% of all classified mammal species worldwide, with about 1,240 bat species divided into two suborders: the less specialized and largely fruit-eating 'megachiroptera', or flying foxes, and the more highly specialized and echolocating 'microchiroptera'.
What do bats eat?
Bats are present throughout most of the world, performing vital ecological roles of pollinating flowers and dispersing fruit seeds.
Many tropical plant species depend entirely on bats for the distribution of their seeds.
Bats are also very important in eating insect pests, reducing the need for pesticides.
How big are bats?
The smallest bat is the Kitti's hog-nosed bat, measuring 29–34 mm (1.14–1.34 in) in length, 15 cm (5.91 in) across the wings and 2–2.6 g (0.07–0.09 oz) in mass. It is also arguably the smallest living species of mammal, with the Etruscan shrew being the other contender.
The largest species of bat are a few species of Pteropus and the giant golden-crowned flying fox with a weight up to 1.6 kg (4 lb) and wingspan up to 1.7 m (5 ft 7 in).
How do bats see in the dark?
Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. By comparing the outgoing pulse with the returning echoes, the brain and auditory nervous system can produce detailed images of the bat's surroundings. This allows bats to detect, localize and even classify their prey in complete darkness.
At 130 decibels in intensity, bat calls are some of the most intense, airborne animal sounds. To clearly distinguish returning information, bats must be able to separate their calls from the echoes they receive. Microbats use two distinct approaches.
1. Low duty cycle echolocation: Bats can separate their calls and returning echoes by time. Bats that use this approach time their short calls to finish before echoes return. This is important because these bats contract their middle ear muscles when emitting a call so they can avoid deafening themselves.
The time interval between call and echo allows them to relax these muscles so they can clearly hear the returning echo. The delay of the returning echoes provides the bat with the ability to estimate range to their prey.
2. High duty cycle echolocation: Bats emit a continuous call and separate pulse and echo in frequency. The ears of these bats are sharply tuned to a specific frequency range. They emit calls outside of this range to avoid self-deafening. They then receive echoes back at the finely tuned frequency range by taking advantage of the Doppler shift of their motion in flight.
The Doppler shift of the returning echoes yields information relating to the motion and location of the bat's prey. These bats must deal with changes in the Doppler shift due to changes in their flight speed. They have adapted to change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range.
For related articles click onto the following links:
INSECT EATING BIRDS
LIGHT POLLUTION AND THE DECLINE IN BAT POPULATIONS
WHAT ARE BATS?
WHICH PLANTS CAN ATTRACT BATS INTO THE GARDEN