There are estimated to be about 1,100 species of bats worldwide, accounting for about 20 percent of all mammal species.

Most microbats are active at night or at twilight.

Many bats migrate, while others pass into torpor in cold weather but rouse themselves and feed when warm spells permit insect activity. Yet others retreat to caves for winter and hibernate for six months.

The social structure of bats varies, with some bats leading a solitary life and others living in caves colonized by more than a million bats. The fission-fusion social structure is seen among several species of bats. "Fusion" refers to the grouping of large numbers of bats in one roosting area and "fission" is the breaking apart and mixing of subgroups, with individual bats switching roosts with others and often ending up in different trees and with different roost mates.

Bat Conservation - http://www.batcon.org/home/default.asp