Free-Tailed Bats and Mastiff Bats: Molossidae

Molossids (mol-LOSS-ids; members of the family Molossidae) range widely in size from small to moderately large bats. They have a forearm length of approximately 1.1 to 3.4 inches (2.7 to 8.5 centimeters), and weigh from 0.2 to 3.8 ounces (5 to 167 grams). Free-tailed bats are named for their thick tail that extends far beyond the tail membrane (thin layer of skin). The mastiff bats are named after their facial resemblance to the mastiff dog.

Some species of molossids have a distinctive wrinkled upper lip, while others have a smooth upper lip. Muzzles of all these bats are generally short and wide and often have wide, fleshy lips that may have folds or creases. Many have a distinctive pad over their noses. The upper surface of this pad often has small horn-like projections. Ears of free-tailed bats are relatively short and thick, often joined across the forehead and point directly forward. The eyes of these bats are relatively small, while the lips are large. All species have long and narrow wings that are thick and, along with the tail, are covered in a leathery membrane. Molossids also have short, strong legs and broad feet. On the outer toes of each foot are curved bristles that the bat uses for grooming its fur.

Molossids generally have short, velvety fur. One group of bats in this family is called the hairless bats because their hair is so short that the animal appears to be naked. Some species have a crest of hairs on the top of the head that stands upright. Fur color may be gray, tan, black, or brown. Many species have two color phases, or types, a reddish one and brownish or blackish color phase.