Microbat

From Freepedia

Microbats

Image:Big-eared-townsend-fledermaus.jpg
Big eared Townsend Bat, Corynorhinus townsendii

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Chiroptera
Suborder:	Microchiroptera Dobson, 1875

Superfamilies

Emballonuroidea
Rhinopomatoidea
Rhinolophoidea
Vespertilionoidea
Molossoidea
Nataloidea
Noctilionoidea

The microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). Other English names are "insectivorous bats", "echolocating bats", "small bats" or "true bats". All these names are somewhat inaccurate, because not all microbats feed on insects, and some of them are larger than small megabats.

The distinctions between microbats and megabats are:

Microbats use echolocation, whereas megabats do not.
Microbats lack the claw at the second toe of the forelimb.
The ears of microbats don't form a closed ring, but the edges are separated from each other at the base of the ear.
Microbats lack the underfur; they have only guard hairs or are naked.

Most microbats feed on insects. Some of the larger species hunt birds, lizards, frogs or even fish. Microbats that feed on the blood of large mammals (vampire bats) exist in South America. Microbats are 4 to 16 cm long.

Echolocation

Bats are the most famous examples for echolocation among animals. Only the microbats (and not the megabats) are able to orient this way. The echolocation system of bats is often called biosonar.

The ultrasounds emerge in the larynx and are expelled through the nose or the open mouth. They have a frequency of 20,000 to 100,000 hertz and are inaudible for the human ear. Due to the high frequency the sounds are concentrated to a narrow beam. Some species have a funnel-shaped nose in order to improve the beam. The range of this beam is up to 5 m.

Sound Sample: Ultrasonic bat calls ▶(?)

There are 800 species of microbats, each of them with a different behaviour pattern. Therefore there are great differences between the echolocation systems of the single species. The following is not valid for all microbats, but for most of them.

Every 150 milliseconds an ultrasound is expelled. That resembles roughly the period of a wing flap or a breath. The sound is reflected by surrounding objects and reaches the bat's ear. The bat is able to determine the distance of objects from the time between expelling and hearing the sound. The sounds may come in shorter intervals, when the bat is going to land or approaching to an obstacle.

Echolocation is not used only for avoiding collisions with objects, but also for hunting the prey. The prey is seized with the mouth, in the case of large prey sometimes with the wings.

Experiments with bats showed that a bat is able to "hear" a wire as thin as 0.08 mm. The echolocation also enables the bat to analyse the surface of an object, so it won't confuse a prey with a plastic object.

Some moths have developed a protection against bats. They are able to hear the bat's ultrasounds and flee as soon as they notice these sounds, or stop beating their wings for a period of time to deprive the bat of the characteristic echo signature of moving wings which it may home in on. To counteract this, the bat may cease producing the ultrasound bursts as it nears its prey, and can thus avoid detection.