The Sunday News
Know Your Wildlife Tsitsi Maponga Assistant Curator ‑ Mammalogy Department
Ndebele — ululwane
Shona — chiremwaremwa
BATS are mammals of the Order Chiroptera whose forelimbs form webbed wings making them the only mammals capable of true flight.
Like all mammals, bats nourish their young ones with milk from the mammary glands. The order Chiroptera is the second largest group of mammals after the rodents, representing about 20 percent of all classified mammal species worldwide.
Bats are useful animals and the best protection for them is for us to learn more about them.
There are about 1240 bat species in the world and these are divided into two suborders:
Megachiroptera (fruit bats) and Microchiroptera (insect eaters).
Not all mega-chiroptera bats are larger than micro-chiroptera bats. The major distinctions between the two suborders are:
(1) Micro-bats use echolocation with the exception of Rousettus genus, mega-bats do not.
(2) Micro-bats lack the claw at the second finger of the forelimb.
(3) The ears of micro-bats do not close to form a ring, the edges are separated from each other at the base of the ear.
(4) Micro-bats lack under fur, they are either naked or have guard hairs.
(5) Mega-bats eat fruits, nectar or pollen most micro-bats eat insects.
(6) Mega-bats have well-developed visual cortices and show good visual acuity while micro-bats rely on echolocation for navigation and finding prey.
The body of the bat is mouse like and usually covered with fine fur. The face varies greatly from one species to another. Many species have complex appendages on the snout and projections or false ears in front of the true ears. The ears themselves are often very large and convoluted. The wings of bats are much thinner than those of birds, allowing bats to manoeuvre quickly and more accurately than birds. They are also delicate and rip easily.
However, the tissue of the bats membrane is able to regrow such that small tears can heal quickly.
Flight has enabled bats to become one of the most widely distributed groups of mammals in the world.
Bats are found in almost every habitat available on earth. Different species select different habitats during different seasons. Bats habitat normally range from seaside to mountains and even deserts. These hand-winged mammals’ habitat has two requirements mainly the roosting place where they spend the day in hibernation and places for foraging especially near a source of water. Bats roosts can be found in hollows, crevices, foliages and even human-made structures, and “tents” that the bats construct by biting leaves.
Most insect eaters are nocturnal and are active at twilight. The social structure of bats varies from one species to another. Some bats lead a solitary life while others roost in caves colonised by more than a million bats. The fission-fusion social structure is fairly common among several species of bats.
The term fusion refers to a large number of bats that congregate in one roosting area especially in caves and individual bats switching roosts with others and often ending up in different trees and with different roostmates. Most bats rest, sleep and hibernate in an upside-down position. They hang on to branches with their feet. The advantage of this is that the energy they spend hanging on is greatly reduced.
Fission refers to splitting from the main group, foraging in small groups during the day.
Also, bats cannot launch themselves into air from the ground, so roosting upside down puts them in an ideal position for takeoff.
Most bats have a breeding season, which is in the spring for species living in a temperate climate. They may have one to two litters in a season depending on the species and environmental conditions such as availability of food and roost sites.
Female bats nurse their young until they are nearly adult size, because a young bat cannot forage on its own until its wings are fully developed.
Female bats use a variety of strategies to control the timing of pregnancy and the birth of the young to make delivery coincide with maximum food availability. These strategies include delayed fertilisation and delayed implantation. The gestation period ranges from 40 days to six months. Bats enjoy a relatively old age, some reaching the age of 20 and in some documented case of a little brown bat (Myotis lucifugus) to 30.
Certainly they attain a longer lifespan than other mammals of similar size such as rodents that live for only one or two years.
Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. This allows bats to detect, localize and even classify their prey in complete darkness. Bats also communicate with one another in a variety of ways. Some of the bats communication calls are audible to the human ear. Scent marks are also important in bats.
Scent is used to communicate reproductive status and individual identity. Many species have scent glands near their faces or their wings. Bats also communicate with visual display often during courtship.
Roles of bats in the ecosystem
Bats are important pollinators and seed dispersers. Many tropical plant species depend entirely on bats for the distribution of their seeds. Also the insect eating bats help in the control of pests. Bats are important as they consume insect pests reducing the need for pesticides. Moreover bats guano (faeces) is rich in nutrients and is used to fertilise crops. The guano can be obtained from caves where bats aggregate in large numbers.
Bats are vulnerable to predators as they roost during the day or emerge in large groups in the early evening. Predators like snakes or hawks often wait near the entrances of caves at dusk attacking bats as they leave the roost. Juvenile bats are also at risk as they cannot fly yet and may fall to the ground.