Mormoops megalophylla Peters 1864
Order Chiroptera : Family Mormoopidae
DESCRIPTION. A medium-sized, reddish-brown or dark-brown bat with conspicuous, leaf-like 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 × 2 = 34. Averages for external measurements: total length, 90 mm; tail, 26 mm; foot, 10 mm; length of forearm, 54 mm. Weight, 15–16 g.
DISTRIBUTION. In Texas this bat is known from the Trans-Pecos, southern edge of the Edwards Plateau, and South Texas Plains. It is typically found in lowland areas, especially desert scrub and riverine habitats, as at Big Bend Ranch, but it also has been captured in the mountainous country of the Apache, Davis, Chinati, Chisos, and Elephant Mountains and in the Sierra Vieja range. It is a common winter (1 November to 15 March) resident of caves along the extreme southern edge of the Edwards Plateau, although its occurrence at specific localities is highly variable and unpredictable. Mormoops megalophylla has been collected at Frio Cave (Uvalde County), Webb Cave (Kinney County), Haby Cave (Bexar County), and Valdina Farms Sinkhole (Medina County) in December through March, May, September, and November, suggesting that it uses the Edwards Plateau caves as a winter retreat. Many apparently suitable caves near those listed above are not used, although they are occupied by bats often associated with Mormoops. In contrast to the winter records from the Edwards Plateau, those from the Trans-Pecos tend to be from the warmer months of the year (March to October). This is suggestive of seasonal migration between the two regions, although such movements have yet to be substantiated.
SUBSPECIES. Mormoops m. megalophylla.
HABITS. Ghost-faced bats typically roost in caves, tunnels, and mine shafts, but they also have been found in old buildings. In addition to the caves listed above, these bats have been taken in a railroad tunnel near Comstock in Val Verde County. Specimens also were captured in January and February in the junior high school at Edinburg. Students found them hanging from the rough plaster ceiling in one of the halls.
Once out of the roost, individuals fly quickly to foraging sites along arroyos and canyons. These bats are relatively strong, fast fliers, and they travel at high altitudes to foraging areas. Foraging may occur over standing water, and these bats often are collected using mist nets positioned over ponds of water along arroyos and canyons. Clyde Jones and his graduate students at Texas Tech University captured many ghost-faced bats under such conditions in Big Bend Ranch State Park (Presidio County) and along Limpia Creek in the Davis Mountains (Jeff Davis County).
Although they may congregate in large numbers at a roosting site (as many as 500,000 individuals), these bats do not form the compact clusters typical of many other species; rather, they tend to space themselves approximately 15 cm apart across the roost ceiling. Therefore, larger sites are required to house great numbers of these bats. Other species that often cohabit roosting sites with Mormoops megalophylla, and that generally greatly outnumber them, include the cave myotis (Myotis velifer) and the Brazilian free-tailed bat (Tadarida brasiliensis).
Few data on the breeding habits of the ghost-faced bat in Texas are available. In Big Bend National Park, two pregnant females, each containing a single embryo, were captured in mid-June. At Big Bend Ranch State Park, 30 pregnant females were taken from 29 April to 9 June, and each contained only a single embryo. Lactating females have been captured there from mid-June to early August. In Coahuila 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.
Their food appears to consist entirely of insects that are captured in flight. The stomachs of two individuals from Big Bend National Park were entirely filled with moths. At Big Bend Ranch State Park, the stomachs of 45 individuals included moths (100% occurrence), beetles (4.4%), true bugs (4.4%), and net-winged insects (2.2%). The bats begin returning to their caves and roosting sites, on average, about 7 hours after they first leave.
POPULATION STATUS. Common, year-round resident. The ghost-faced bat is probably not as rare within its geographic range as previously thought. At Big Bend Ranch State Park in Presidio County, at Big Bend National park in Brewster County, and at collecting sites in the Davis Mountains, it was one of the most common bats collected.
CONSERVATION STATUS. The ghost-faced bat's status is listed by the IUCN as least concern because of its wide distribution and occurrence in protected areas; however, it is thought to be in a decreasing population trend. It is not on the federal or state lists of concerned species. The wintering cave populations, along the southern edge of the Edwards Plateau, roost at just a few sites and could be susceptible to disturbance and disruption. All cave-dwelling bats are vulnerable because large segments of a regional population often roost at a single site where they are susceptible to disruption, disturbance, and extirpation.
From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016. Courtesy of the University of Texas Press.