Volume 34
Issue 4
Mexican long-nosed bat
Mexican long-nosed bat (Leptonycteris nivalis) Credit: Merlin D. Tuttle

The Mexican long-nosed bat (Leptonycteris nivalis) is a nectar-feeding bat native to Mexico and the United States. Its characteristic elongated muzzle makes it well-adapted to feeding on nectar and protein-rich pollen. Its tongue, which can be extended up to 3 inches, allows it to reach deep down into flowers. Mexican long-nosed bats are the largest nectar-feeding bats in the New World; they are very strong, highly maneuverable fliers, and somewhat like hummingbirds, they are able to pause in flight to feed on the showy flowers of plants, such as the agave or century (Agave spp.) plant.

The Mexican long-nosed bat is classified as endangered in both the U.S. and Mexico. In order to understand this bats life history and recent decline, one must understand its feeding ecology. Although movement patterns are not precisely known, this migratory species is thought to move from central Mexico into northern Mexico each year, with part of the population crossing the border into Texas and New Mexico. This migratory pathway follows a nectar corridor as the bats migrate to follow the blooming periods of a number of agave and cacti species found in the regions desert scrub habitats.

The Mexican long-nosed bat and a similar-looking species, the lesser long-nosed bat (Leptonycteris yerbabuenae), are the main pollinators of several agave species, including Agave angustifolia (one of the mezcal species), A. salmiana (pulque plant) and A. tequilana (tequila plant), and are renowned for their association with the tequila and mezcal that humans make from the agaves.

agave fields
The Mexican long-nosed bat feeds on the nectar of the agave plant.
Credit: Credit Alfredo Flores-Zaher

While both bats feed on agave, the species coexist only in a small overlapping area. The Mexican long-nosed bat prefers higher, cooler places in parts of New Mexico, Texas and Mexico, whereas, the lesser long-nosed bat generally inhabits lower elevations in New Mexico, Arizona, Mexico and parts of Central America. Agave plants are the primary source of nectar for Mexican long-nosed bats, and although population declines are not entirely understood, some think they might be connected to a loss of food resources, through both changing land use and wild agave harvesting.

A loss of roosting sites is another factor thought to impact the populations of Mexican long-nosed bats. For day roosting, the bats depend on cool caves, crevices, abandoned mines, tunnels and old buildings. There is only one known mating site for this species: in the central Mexican state of Morelos. In this cave, males and females gather during the winter, and in March females start migrating north. Females are then believed to give birth to one or two young each year. The young are born in northern Mexico during April, May and early June, then move further north with their mothers, following the blooming periods of the agaves and cacti. In Big Bend National Park in Texas, agaves begin blooming in mid-May at lower elevations and early June at higher altitudes. The bats arrive in Texas about a month after the flowering of agaves has begun and spend most of the summer there, before following the later-blooming agaves southward in late summer or early fall. Few adult males have been recorded in Texas and northern Mexico, as males and females segregate geographically, with males rarely appearing in the most northerly part of the species range. From late October to February, adult males and females congregate in the same cave in Morelos again to mate.

Mexican long-nosed bat
Mexican long-nosed bat (Leptonycteris nivalis)
Credit: Leonora Torres Knoop

Many aspects of Mexican long-nosed bat biology remain a mystery to scientists and conservationists alike. Because of the species migratory nature and a lack of knowledge about its roosting sites, it is very difficult for conservationists to get accurate population estimates. To try to answer some of these questions, BCI is working with Dr. Rodrigo Medellin, coordinator of the Program for Conservation of Mexican Bats (PCMM) to search for additional mating sites for this species in central Mexico. While the search continues, BCI and the PCMM are working with community partners in Morelos to protect the only known breeding site for the species. BCI is also investing in identifying and protecting vital agave fields along the nectar corridor that Mexican long-nosed bats rely on for survival. While these are all important steps, a revised long-term recovery plan, with committed partners in both Mexico and the United States, is desperately needed. BCI is currently building an international collaborative team to come together to revise the science and commit to actions to help save this species.