Mammal diversity: monotremes, marsupials, bats and rodents

Bats are the only mammals adapted to true flight: the forelimbs have become wings, with a thin skin membrane stretched between the fingers and the sides of the body, forming the lifting surface. The first finger and the hind feet are free, and bats hang by them from cave walls or trees. Bats have weak eyes but fly at night without hitting anything and catch insects: they emit intermittent ultrasound from mouth and nose, the sound returns from an obstacle or prey like an echo, and the ear receives it, so the animal locates objects. In one night a bat eats a great many mosquitoes and harmful insects, so their shelters should not be destroyed. Rodents have no canines, and have large, sharp incisors; they gnaw hard food with the incisors and crush it with the cheek teeth. Because the back of an incisor lacks enamel, the tooth wears and sharpens itself and keeps growing throughout life. Members of this order live almost everywhere and multiply fast, breeding several times a year, so their numbers can surge and cause harm. In settlements live mice and rats, in deserts ground squirrels, in the foothills the porcupine (its body covered with long quills). Most rodents are pests: mice and rats gnaw grain and goods, and rats can spread diseases such as plague. Muskrats, nutria, marmots and ground squirrels are hunted for fur; muskrat and nutria came from America. Menzbier’s marmot of the Western Tian Shan is in the Red Book because it has declined. Safety: do not touch bats or rodents (they can spread disease) or dead rodents; do not go near marmot or ground-squirrel burrows – tell adults.