Velvety Free-Tailed Bat

Photo of the Velvety Free-tailed Bat, Murci��lago Casero

PallasMastiff Bat, Velvety Free-tailed Bat, House Bat (Eng.), Murciago Casero, Murciago Mast Com (Sp.), Molossus molossus fortis (Sci.); native, Puerto Rico and the US and British Virgin Islands.

Photo 2005 Museum of Antigua & Barbuda. Information compiled by Alan Mowbray, Interpretive Media Writer, EYNF/LEF

General Information

Pallas’ Mastiff Bat (Molossus molossus fortis), also called Velvety Free-tailed Bat and House Bat is of the Order Chiroptera; Family Molossidae; Genus Molussus; a small genus with 20 or less known species. Members of this family have tails extending well beyond the edge of the tail membrane. All have short, dense fur and emanate a musky odor. Molossidae bats range from Mexico to Argentina, including the Caribbean islands, and the Florida Keys.


Molossus molossus fortis is a medium sized bat, weighing just 0.5 ounces (15 grams), with a forearm measuring 2 1/3 to 2 5/8 inches (59 to 61 millimeters), and high aspect ratio wings that are very long and narrow, facilitating fast and efficient flight. Their long and narrow wings require them to gain speed before flight to attain lift; they must drop vertically from their perch before they extend their wings. Molossus molussus fortis has reddish-brown to black fur and a tail that protrudes free from the tail membrane. Although similar in appearance to the Mexican free-tailed bat (Tadarida brasiliensis), the Pallasmastiff bat has ears that lay forward and are joined at the base.


Pallas’ Mastiff Bat adults are insectivores with a diet consisting primarily of mosquitoes and other airborne insects. Like most bat species, Molossus molossus are crepuscular, becoming active at twilight or just before sunrise. It is one of the first bats to emerge at dusk and one of the last to return to the roost at dawn.


Pallas’ mastiff bats are known to roost in hollow trees and snags, palm fronds, rock crevices, and caves, in hardwood forests. They will also find roosts in houses.

Where to look for this animal in the EYNF

Bats will typically emerge at twilight near the El Portal or Big Tree Nature trails in the Forest’s recreation area.