Ghost-faced Bat
Order Chiroptera : Family Mormoopidae : Mormoops megalophylla Peters

Description. A medium-sized, reddish-brown or dark brown bat with conspicuous, leaflike appendages on chin; ears short, rounded, united across forehead; lower part of ear forming a copious pocket below eye; tail projecting dorsally from near middle of interfemoral membrane; crown of head highly arched; skull markedly shortened, cranium high and abruptly arched. Dental formula: I 2/2, C 1/1, Pm 2/3, M 3/3 X 2 = 34. External measurements average: total length, 90 mm; tail, 26 mm; foot, 10 mm; length of forearm, 54 mm.

Distribution in Texas. Known from the Apache Mountains (Culberson County), southern Trans-Pecos, southern escarpment of the Edwards Plateau, and extreme South Texas.

Habits. This is a colonial, cave-dwelling bat whose distribution is closely correlated with the distribution of caves, crevices, and abandoned mine tunnels which serve as daytime roosts. A colony of about 6,000 individuals was found in Frio Cave near Concan in February and March, 1955. This cave may serve Mormoops chiefly as a winter retreat because from April through August none has been found there. In contrast, records from Trans-Pecos Texas are from these warmer months of the year, suggesting the possibility of seasonal migration between the two regions. Such movements have yet to be substantiated, however. At Frio Cave the population begins building up in September, and by mid-November it approaches maximum size. Smaller colonies of Mormoops inhabit Haby Cave and Valdina Farms Sinkhole in Medina County and Webb Cave in Kinney County. They have also been taken in a railroad tunnel near Comstock in Val Verde County. Members of a Mormoops colony roost singly, spread out over the ceiling of the cave about 15 cm apart. There are no compact clusters as one finds with most cave-dwelling bats.

Mormoops also may roost in buildings. Four Texas specimens were captured in the Junior High School at Edinburg. Students found them hanging from the rough plaster ceiling in one of the halls. The bats apparently entered the building through open windows at night. One specimen was captured in February, the others in January.

Their food appears to consist entirely of insects which are captured in flight. The stomachs of two Mormoops from Big Bend National Park were entirely filled with moths. Mormoops probably forages relatively high above the ground in areas unobstructed by tall vegetation. The bat is a strong, swift flier that hits a mist net with considerable force, although few of them have been caught in such nets. In Yucatan, however, Mormoops have been captured in mist nets set "in or near forests," and in southern Chiapas, Mexico, they have been taken in nets set across a tree-bordered, shallow stream where about a dozen species of bats came to drink.

Little data on the breeding habits of Mormoops in Texas are available. In Big Bend National Park two pregnant females, each containing a single embryo, were captured in mid-June. Lactating females have been captured there from mid-June to early August. In Coahuilla and Nuevo Leon, two Mexican states bordering Texas, gravid females have been captured in March, April, and May. Each gravid female contained a single embryo. Based on data collected in Central America and Mexico, it seems that in this species mating begins in late December. Sexually mature females taken between January and June are likely to be gravid or lactating; no gravid females have been reported from late June through January. Thus, it appears that the period of reproduction is confined to late winter and early spring, even in the tropics, and that each reproductively active female gives birth to only one offspring each year.

Photo credit: Merlin D. Tuttle, Bat Conservation International.