Bats are the only flying mammals. They give birth to live young and nourish them with milk. Bats are nocturnal; they are most active at night and sleep during the day hanging upside-down. They are found in all types of habitats all around the world except at the poles.

There are over 900 different species of bats. The smallest bat is the bumblebee bat (with a wingspan of 6 inches=15cm, weighing less than a penny); the biggest bat is the flying fox bat (with a wingspan of 6 feet=1.8m, weighing 2 pounds=1kg). During the cold winter, some bats migrate to a warmer area. Some bats (like the brown bat) hibernate during the cold of winter, sleeping very deeply until warm weather arrives.
------Classification ----
Bats belong to the class Mammalia (mammals) and the order Chiroptera (bats). There are two types of bats that differ in their diet and in the way they sense and obtain food. Bats are divided into:
---- Microchiropterans----
These bats use echolocation to find insects and small animals to eat. While flying, these bats send out high-pitched sounds that bounce off other objects. The bat listens for the bounced sound, and can determine where objects are located. People cannot hear these high-pitched sounds.
Some Microchiropterans are the vampire bat and the frog-eating bat. The vampire bat is the only bat (and the only mammal) that eats only blood. It makes a small hole with its two very sharp incisor teeth and laps up the blood, which doesn't clot because of anti-coagulants in the bat's saliva.
----- Megachiropterans ---- These large bats use the sense of smell to find their food, fruit and/or nectar. Some Megachiropterans are the fruit bat and the blossom bat.