Animal echolocation in the external ear. There are two hypotheses about the evolution of echolocation in bats. The first suggests that laryngeal echolocation evolved twice in Chiroptera, once in the Yangochiroptera and once in the horseshoe bats (Rhinolophidae). The second proposes that laryngeal echolocation had a single origin in Chiroptera, was subsequently lost in the family Pteropodidae (all megabats), and later evolved as a system of tongue-clicking in the genus "Rousettus". Individual bat species echolocate within specific frequency ranges that suit their environment and prey types. This has sometimes been used by researchers to identify bats flying in an area simply by
Do not feed the animals animals aggressively seeking out food from people, sometimes resulting in injury. Zoos generally discourage visitors from giving any food to the animals. Some zoos, particularly petting zoos, do the opposite and actively encourage people to get involved with the feeding of the animals. This, however, is strictly monitored and usually involves set food available from the zookeepers or vending machines, as well as a careful choice of which animals to feed, and the provision of hand-washing facilities to avoid spreading disease. Domestic animals such as sheep and goats are often permitted to be fed, as are giraffes. In national parks