Lesser Long-nosed Bat

Leptonycteris curasoae yerbabuenae

Description

Lesser long-nosed bat, Leptonycteris curasoae yerbabuenae, also commonly known as Sanborn's long-nosed bat, is 2.75-3.5 in (7-9 cm) long and weighs 0.5-1 oz (18-30 g). It has a long tongue, reaching up to 3 in (7.6 cm), and an elongated muzzle. Its fur is yellowish brown or grayish above and cinnamon brown below. Though very similar to the Mexican long-nosed bat (L. nivalis ), the lesser long-nosed bat has shorter, denser fur, as well as different cranial and dental characteristics. This species has shorter, denser eplage while Mexican long-nosed bat has longer, finer hair extending above the tail membrane.

This bat has also been classified as L. yerbabuenae and L. sanborni yerbabuenae.

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. The plants and bats are mutually dependent. These plants need the bats as pollinators, and if the plants are destroyed the bat population suffers. The muzzles and tongues of the lesser long-nosed bats are highly adapted for 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. In the southern portion of its range, the lesser long-nosed bat feeds on soft and juicy fruits.

Habitat

This bat inhabits caves, tunnels, and mines, often returning to the same chambers over several years. It is found in arid scrub in the northern part of its range. In the southern portion of its range it is found at high elevations.

Distribution

The lesser long-nosed bat is known from central Arizona and southwestern New Mexico, through Mexico to El Salvador. The species is known to have formed very large roosting colonies, sometimes as many as 20,000 individuals, but recent surveys have not found such large colonies. Historically, this bat was once more common in the United States than the related Mexican long-nosed bat. Colossal Cave in Pima County, Arizona, known to contain as many as 20,000 roosting lesser long-nosed bats during the 1950s, is no longer inhabited. A 1974 survey of all localities in the United States from which this species was known was only able to locate 135 individuals.

This bat currently occurs in very small numbers across its U.S. range. Recent surveys of known sites in Arizona and New Mexico found the bat in only one location, a cave on private property in Santa Cruz County, Arizona, containing about 500 individuals. Reports of bats feeding at artificial hummingbird feeders in Cochise County, Arizona suggest the existence of two additional populations there.

Surveys over the early 1980s covered all sites in Mexico from which the lesser long-nosed bat was known. Only three roosting populations were found; a small number was found in two locations; at a third cave near the coast of Jalisco, as many as 15,000 L. curasoae were located. An unconfirmed 1987 report counted as many as 3,000 lesser long-nosed bats in the Santa Rita Mountains, close to where the largest colony was sighted in 1985. There were also reports of 800-1,000 bats at Sonora, Mexico, in May 1986. The record of L. curasoae in El Salvador dates from a single specimen found in 1972.

Threats

Human disturbance has been the main cause of the decline of the lesser long-nosed bat. In addition, since it is dependent on specific plants for food, any decline of these plants is devastating to bat populations.

Unfortunately, the continued survival of this bat's food plants in their historic numbers is in doubt, especially in Mexico. Human exploitation of plants for food, fiber, and alcoholic beverages, and the clearing of land for agricultural and livestock purposes has destroyed large numbers of these 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. Recreational spelunkers have also caused bats to abandon roosting sites.

Conservation and Recovery

Habitat protection is the most important objective for recovery. Caves and abandoned mines need to be preserved for roosting sites, and protected from vandals. The breeding site on private land in Pima County needs to be relieved of human disturbance. Stricter law enforcement against moonshiners who pilfer the agave plants is required; reestablishing the agave and columnar cacti populations will increase the bats' chances of survival.

A former roosting site for this bat has been renovated in Pima County, and some bats have returned to use it. Other caves in the area could also be restored to the bats' requirements.

One population of bats was discovered on a U.S. Army base in Fort Huachuca, Arizona in 1989. The Endangered Species Act requires the army base to manage controlled burning of the bats' habitat, and restrict training exercises, firing range activities, and recreational access to the caves and mines on the base.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103
http://southwest.fws.gov/

References

U.S. Fish and Wildlife Service. 1988. "Determination of Endangered Status for Two Long-nosed Bats." Federal Register 53: 38456-38460.

U. S. Fish and Wildlife Service. 1988. "Two Long-nosed Bats." Endangered Species Technical Bulletin. Vol. XIII, Nos. 9-10. pp. 5.

Wilson, D. E. 1985. "Status Report: Leptonycteris sanborni Hoffmeister, Sanborn's Long-Nosed Bat." Report to the U.S. Fish and Wildlife Service, Albuquerque.