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The Mammals of Texas -
Online Edition Mexican Long-nosed Bat
Habits. This is a colonial, cave dwelling bat that usually inhabits deep caverns. The only known colony of these bats in the United States is found in a large cave on Mt. Emory in Big Bend National Park. The number of bats using the cave fluctuates widely from year to year with yearly estimates of population numbers ranging from zero to 13,650. Reasons for this instability are unknown, but it may be that this colony forms only in years when over-population or low food supply in Mexico force the bats to move northward. This bat has recently been classified as endangered by the U.S. Fish and Wildlife Service. At the Emory Peak cave, L. nivalis forms a large cluster with half-grown young and adults intermingled. Adult males and females may be present. They share the cave with a large colony of big-eared bats (Plecotus); each colony roosts in a different part of the cave, but not more than 6 m apart. The air in this cave in considerably cooler in summer than that outside, and a distinct breeze blows through it at all times. The cave is not used in winter; the inhabitants migrate to Mexico. This bat has a strong, musky odor similar to that of the Brazilian free-tailed bat. L. nivalis feeds on the nectar and pollen of flowers, especially those of the century plant (Agave sp.). The seasonal occurrence of L. nivalis in Texas is probably related to food availability as their presence seems to coincide with the blooming of century plants in June. These plants open their flowers at night and attract bats with copious amounts of nectar. As the bats feed, their fur gets coated with pollen grains. When they fly to another plant in search of more food, they transfer the pollen to a new flower, assisting in cross-fertilization of the plants. This mutual relationship is so strong that both the bats and the century plants cannot survive without the other. As the flower stalks of the agaves die by late summer, the bats disappear as there is nothing left for them to eat. The breeding season is restricted to April, May, and June. Females give birth to one young annually. The young are born in Mexico, prior to the bats’ arrival in Texas, and are weaned in July to August, which is the peak of the rainy season and the peak of flower abundance. Photo credit: Merlin D. Tuttle, Bat Conservation International. |
Description. A medium-sized bat with
short ears, no tail, and a distinct nasal leaf; forearm
furred above at elbow; upperparts drab brown, the hairs
white basally; underparts pale drab, tips of hairs
silvery. Dental formula: I 2/2, C 1/1, Pm 2/3, M 2/2 X 2
= 30. External measurements average: total length, 83 mm;
foot, 17 mm; ear, 15 mm; forearm, 58 mm. Weight, 24 g.