Free-Tailed Bats and Mastiff Bats: Molossidae

Like many insect-eating bats, molossids eat many insects that humans consider to be pests. The one hundred million Mexican free-tailed bats that live in Texas in the summer eat an estimated 1,000 tons (907 metric tons) of insects each night, many of which destroy crops. In California and other areas, farmers build bats houses to attract these bats so they will eat the pests. People also collect the bat droppings (guano; GWAH-no) of molossid bats that live in large colonies, using the guano as a fertilizer as it is rich in nitrogen. Some species of these bats have also been associated with spreading disease, such as rabies. Rabies is a viral infection that attacks the nervous system and can be deadly.

People have caused the decrease in population of molossids by destroying and disturbing their natural habitat. These bats have also been harmed through eating insects that have come into contact with pesticides, chemicals designed to control pests.