Claim: Bats are mammals.

Bats are mammals of the order Chiroptera -LRB- -LSB- kaɪˈrɒptərə -RSB- from the χείρ - cheir , `` hand '' and πτερόν - pteron , `` wing '' -RRB- whose forelimbs form webbed wings , making them the only mammals naturally capable of true and sustained flight . By contrast , other mammals said to fly , such as flying squirrels , gliding possums , and colugos , can only glide for short distances . Bats are less efficient at flying than birds , but are more manoeuvrable , using their very long spread-out digits which are covered with a thin membrane or patagium .   Bats are the second largest order of mammals -LRB- after the rodents -RRB- , representing about 20 % of all classified mammal species worldwide , with about 1,240 bat species divided into two suborders : the less specialized and largely fruit-eating megabats , or flying foxes , and the highly specialized and echolocating microbats . About 70 % of bat species are insectivores . Most of the rest are frugivores , or fruit eaters . A few species , such as the fish-eating bat , feed from animals other than insects , with the vampire bats being hematophagous , or feeding on blood .   Bats are present throughout most of the world , with the exception of extremely cold regions . They perform the vital ecological roles of pollinating flowers and dispersing fruit seeds ; many tropical plant species depend entirely on bats for the distribution of their seeds . Bats are economically important , as they consume insect pests , reducing the need for pesticides . The smallest bat is the Kitti 's hog-nosed bat , measuring 29 - in length , 15 cm across the wings and 2 - in mass . It is also arguably the smallest extant species of mammal , with the Etruscan shrew being the other contender . The largest species of bat are a few species of Pteropus -LRB- fruit bats or flying foxes -RRB- and the giant golden-crowned flying fox with a weight up to 1.6 kg and wingspan up to 1.7 m.   The Mexican free-tailed bat is the fastest flying animal in horizontal flight .