Bat prevent them from spending too much time in unfamiliar places, and decrease predation. In some species, pregnant individuals may not use torpor. The smallest bat is Kitti's hog-nosed bat ("Craseonycteris thonglongyai"), which is long with a wingspan and weighs . It is also arguably the smallest extant species of mammal, next to the Etruscan shrew. The largest bats are a few species of "Pteropus" megabats and the giant golden-crowned flying fox, ("Acerodon jubatus"), which can weigh with a wingspan of . Larger bats tend to use lower frequencies and smaller bats higher for echolocation; high-frequency echolocation is better at detecting
Animal echolocation transition (14 Ma), with the divergence of odontocetes and mysticetes occurring with the former, and the speciation of delphinioidae with the latter. There is a strong connection between these proteins, the ocean restructuring events, and the echolocation evolution. One specific type of echolocation, narrow-band high frequency (NBHF) clicks, evolved at least four times in groups of odontocetes, including the pygmy sperm whale (Kogiidae) and porpoise (Phocoenidae) families, "Pontoporia blainvillei", the genus "Cephalorhynchus", and part of the genus "Lagenorhynchus". These high frequency clicks likely evolved as adaptation of predator avoidance, as they inhabit areas that have many killer whales and the