Suborder Microchiroptera

• Of the two suborders of bats, these are the bats most people around the world are more familiar with, as they are found practically everywhere.

• They are a much more diverse group than the 'Megabats'.

• There are 17 families, 135 genera and over 759 species (Robson 2002).

• There are microchiropterans that have evolved to feed on insects, fish, fruit, nectar, blood and even other bats.

• Most live in colonies in dark places where they roost upside down.

• They tend to be much smaller (sometimes tiny), have tails (with the flying membrane stretching between the legs and tail), use echolocation, are broadly insectivorous and have only one claw on the forelimbs (Robson 2002).

• The saying 'blind as a bat' is a reflection of the fact that many species have small eyes and that they tend to rely on another sense to make their way around.

• This other sense involves emitting high frequency calls from the throat, and projecting out the mouth or nose to detect the 'ultrasounds' as they reflect off other objects (echolocation).

• They use this echolocation sense both to navigate in the dark and to locate their prey.

• Many people around the world fear these bats for various reasons. Many of these reasons are unfounded, but one has to admit that when examined in the hand, they often have rather grotesque faces with various foldings in the skin. These convolutions may aid in making and collecting their ultrasonic calls (Strahan 1998).

Suborder Megachiroptera

• This larger family of bats has a  total of over 40 genera and over 160 species.

• The largest, an Asian species has a wingspan of one and a half metres (Strahan 1998).

• Like the Microchroptera, these animals usually roost communally, hanging upside down.

• Unlike their smaller relatives however, they tend not to sleep in dark places, but roost hanging off trees.

• And unlike the smaller bats they tend not to have tails, and have two claws on their forelimbs (Robson 2002).

• Also unlike their smaller relatives, they tend to feed not so much on insects, but on fruit and/or nectar.

• Because of this difference in diet, much about their biology is also quite different.

• They generally don't have echolocation; only one African species can echolocate, but even this is actually performed in a different way from the Microchiropteran bats, with the clicking of the tongue, much like swiftlets (Robson 2002).

• The lack of echolocation means Megabats do not have the strange convoluted folds of the smaller insect bats, and thus tend to have much simpler and more attractive fox or dog like faces.

• Instead, they have much better developed senses of sight and smell, and these are used in locating fragrant flowers and ripening fruit.

• Their diet of flowers and large fruits means they are largely restricted to the more tropical forests of the world.

• Of these warmer regions, they are only found in the 'Old World' of Africa, Asia and Australasia.

• They are notably missing from the 'new world', where some of the smaller Microchiropteran have filled in similar niches and are even locally known as 'fruit bats' (Emmons and Feer 1990).

Evolution of the Chiropterans

• Arguments that have risen about the evolutionary history of flying fox in the last few decades, for their was some evidence suggesting the Megachiropteran bats may be more closely related to primates than the Microchiropteran bats (Pettigrew 1988).

Rainforest Bats

• The scientific name for bats (Chiroptera) originates from the Greek words of kheir (meaning hand) and pteron (meaning wing).

• They are warm-blooded and have fur or hair, and feed their young with milk.

Distribution:

• Queensland is home to a recorded 52 species of bats (out of 92 species in Australia).
• Present and past distributions of bats indicate that they originated in tropical forests. They probably reached Australia about 26 million years ago when land connections existed between some of the islands between New Guinea and north Queensland.
• In general, tropical non-hibernating bats are restricted to north of the Tropic of Capricorn. Colonisation of temperate climates depends on the ability to hibernate during seasonal food shortages such as winter.

Flight:

• They are the only mammals capable of sustained flight.
• Bats’ forelimbs have undergone dramatic changes during their evolution to allow them to function as wings. They have the same basic parts as the human hand and arm, only in very different proportions. Their upper arm is shorter, their forearm is longer, and all the toes except the thumb are greatly elongated.
• Their wing consists of a thin membrane with a leading edge extending from the shoulder to the base of the thumb and to the tips of the second and third toes and a trailing edge extending from between the tips of the third, fourth and fifth toes to the ankle. The thumb is free of the wing membrane and bears a claw for use in crawling, support and grooming.
• Muscles that pull the forearm towards the chest mainly power flight and, to provide a surface for attachment of these large muscles, the breastbone is keel-shaped, as in flying birds.

Temperature Control:

• As most bats are small, they have relatively large body surface areas from which body heat can be lost by radiation. Their extended wings can act as radiators. Warm surroundings reduce heat loss too. Humid tropical conditions and lots of drinking water prevent potential water loss problems.
• Bats may become torpid (dormant) in cold regions when resting by switching off their internal thermostat and letting their body temperature drop to that of their surroundings. This reduces the animal’s rate of energy consumption as its metabolism slows and less heat is lost by radiation to the environment.

Energy and Metabolism:

• A bat must ingest larger quantities of food than a terrestrial mammal of similar size as much more energy is spent in flying than in other modes of locomotion.
• The rate of metabolism may be as little as one percent of the rates when flying and the heart rate may be correspondingly slower. As this state also requires some energy, a store of fat laid down in the body of the bat in the time just prior to hibernation is needed.

Breeding:

• Bats have two alternative reproduction cycles associated with hibernation. The first is the storage of sperm in the female reproductive tract from autumn to spring. This allows the female to fertilise an ovum as soon as hibernation ends. The second method is for an ovum, usually fertilised in autumn, to develop to an early embryonic stage and then remain at ease until spring, when development continues.
• Gestation period is between 50 and 240 days – relatively long for small mammals.
• The period of maternal dependence is also long – 3 to 10 weeks.
• Usually one young is born each breeding season.
• It is blind (except in fruit bats) and hairless.
• Females suckle their young from two nipples, one under each armpit. In some groups there is a false (non-lactating) nipple in each groin, onto which the young may attach itself by its teeth.

Additional Information:

• Bats have been considered as objects of mystery, superstition, fear and worship. They are important in medical research when studying problems like hypothermia, survival in extreme environments, and topics of comparative anatomy, embryology, histology and cytology.
• Bats make a practical contribution to the environment in the form of tree pollination and insect control. Flying foxes are the primary agents for pollination of many Australian hardwood forests.
• Many bat species need protection if they are to be maintained in a sufficiently large area, in numbers high enough for reproduction. Australia protects bats by law.
• Bats are second only in number to the rodents: about 40 percent of living mammal species are rodents, and about 20 percent are bats.

Additional Information:
Tolga Bat Hospital