Mexican Long-nosed Bat

Leptonycteris nivalis

Description

The Mexican long-nosed bat, Leptonycteris nivalis, is 2.75-3.5 in (7-9 cm) long and weighs 0.6-1 oz (18-30 g). The bat has a long tongue, reaching up to 3 in (7.6 cm), and an elongated muzzle. The fur is normally yellowish-brown or grayish above and cinnamon below. Though similar in appearance to the endangered lesser long-nosed bat (L. curasoae yerbabuenae ), the Mexican bat has finer hair, extending above and beyond the tail membrane, as well as different cranial and dental characteristics.

Behavior

The migration pattern of this species is associated with the flowering of agaves, the giant saguaro, and the organ pipe cacti. This bat feeds on the nectar and pollen of paniculate agaves (century plants) and large cacti—a phenomenon known as chiropterophily. These plants and the bats seem to be mutually dependent. The plants require the bats as pollinators, and if the plants are destroyed the bat population declines.

The muzzles and tongues of long-nosed bats are highly adapted to deep insertion into flowers and collection of pollen particles. Paniculate agaves produce accessible and showy night-blooming flowers with pollen that is rich in protein. The bat also feeds on soft and juicy fruits at the southern end of its range.

Habitat

The Mexican long-nosed bat inhabits caves, tunnels, and mines along its migration route, often returning to the same chambers over several years. Adapted for life in arid country, it is found feeding in arid scrub in the northern part of its range. In the southern part of its range, it is sometimes found at high elevations on wooded mountains. While thousands of individuals were once seen at some roosting sites, such large aggregations are now rare.

Distribution

The Mexican long-nosed bat is known from southwestern New Mexico and Texas south through much of Mexico and into Guatemala. The presence in New Mexico is based on two specimens collected during 1963 and 1967 in Hidalgo County. The reported occurrence in Guatemala is based on specimens collected in the late nineteenth century. The species is known to have formed very large roosting colonies, sometimes as many as 10,000 individuals, but surveys no longer find colonies of this size. The only Mexican long-nosed bat roost site currently in use in the United States is a cave in Big Bend National Park, Brewster County, Texas. Surveys estimated 10,650 bats in 1967 but only about 1,000 bats in 1983. Surveys of all historically known sites in Mexico have found bats in 15 localities— most in relatively low numbers. An abandoned mine in the state of Nuevo Leon utilized as a roost by 10,000 individuals in 1938 was empty in 1983. The ceiling of another mine in Nuevo Leon was covered by newborn young in 1967, but contained only a single bat in 1983. The largest group found during the 1983 survey consisted of 30-40 individuals in a cave near Morelos (in the state of Coahuila) that formerly supported a large colony during the 1950s and 1960s. As of 1994 when the recovery plan for the Mexican long-nosed bat was released by the U.S. Fish and Wildlife Service (FWS), the 1983 figures were the latest available for the species.

Threats

Well-known caves have been the roosting habitat of this species, and human visitation has been a direct cause of their decline. Additionally, as this bat is highly dependent on specific plants for food, any decline in these food plants can prove devastating. Unfortunately, the continued survival of these food plants in their historic quantities is in doubt, especially in Mexico. Human exploitation for food, fiber, and alcoholic beverages, and land clearing for agricultural use are destroying large numbers of plants. Some paniculate agave plants are being intensively harvested by "moonshiners" for tequila production. As plants are destroyed, the bat population suffers and the overall fecundity of paniculate agave declines.

Although the bat is not carnivorous, there is the mistaken but widespread belief across Mexico that all bats feed on the blood of livestock and humans. As a result of this, vandals have entered caves and killed bats, including such harmless species as the Mexican long-nosed. Recreational spelunking has also caused the bat to abandon roosting sites.

Conservation and Recovery

The 1994 species recovery plan has the goal of downlisting the species to threatened, possibly as early as 2014 if recovery criteria are met. These criteria call for there to be at least six populations and for the supporting habitat to be protected; for the six populations to be maintained for 10 consecutive years; and for information to indicate that the populations and their supporting habitat will continue to be maintained. To achieve recovery goals, the plan outlines major actions needed, including the development of effective roosting and foraging habitat protection; the implementation of increased public education programs; and the monitoring of colonies and populations through the range. The plan also calls for applicable ecological studies into demography, feeding ecology, and roost use. The Mexican long-nosed bad has a recovery priority of 5; according to the FWS's criteria, this indicates a species with a high degree of threats and a low potential for recovery.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

References

Howell, D. J., and N. Hodgkin. 1976. "Feeding Adaptations in the Hairs and Tongues of Nectar-Feeding Bats." Journal of Morphology 148: 329-336.

U. S. Fish and Wildlife Service. 1994. "Mexican Long-Nosed Bat Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.

Wislon, D. E. 1985. "Status Report: Leptonycteris nivalis (Sassure), Mexican Long-Nosed Bat." Report to U. S. Fish and Wildlife Service, Albuquerque.