The Bumblebee Bat
According to the Animal Diversity Web Thailand's bumblebee bat (a.k.a. Kitti's hognosed bat or Craseonycteris thonglongyai) competes with the Etruscan pygmy shrew for the title of world's smallest mammal. At issue is whether skull size or mass defines "smallest"; shrews are lighter but the bumblebee's skull is smaller at 11mm.
These bats are so-named since they're about the size of a bumblebee, weigh about as much as a dime, and have the ability to hover like hummingbirds. Their roosting habitat consists of the hot upper chambers of caves in limestone hills. They are most active at dusk when they fly around the tops of bamboo clumps and teak trees to feed on insects.
Craseonycteris thonglongyai is a colonial animal, roosting in groups in caves (Macdonald, 1984). However, an individual within a group is solitary. Though close to others in its group, it hangs alone, rather than clustering tightly. It is most active at dusk, at which time it flies around the tops of bamboo clumps and teak trees (Nowak and Paradiso, 1983).
The bumblebee bat is endangered and rare, a CITES list animal. The total population is estimated at two hundred individuals.
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