Is The Lesser Long-Nosed Bat Endangered? New Colonies Discovered But Border Wall and Migration Pose Hazards
Listed as endangered in 1988, the lesser long-nosed bat (Leptonycteris curassoae yerbabuenae), is one of the few species of bat to undertake long distance migration. Lesser long-nosed bats feed on nectar, pollen and columnar cactus fruit. Roosting occurs in hot, humid caves, with thousands of other bats of the same and other species which conserves heat and prevents dehydration.
Lesser Long-Nosed Bat Migration
The subspecies of lesser long-nosed bat found in the United States and northern Mexico migrates between the southern United States and Mexico. Along that migratory route, food in the form of cactus flower and agave nectar must be found. Migratory corridors must also contain stopover shelters for the bats along the way.
In addition, within this bat subspecies there appear to be two distinct subpopulations, one which migrates from northern Mexico to summer maternity roosts in the United States and the other, which migrates further south into southern and central Mexico utilizing winter maternity roosts. This means that the two subpopulations are not likely to interbreed.
Lesser Long-nosed Bat Migratory Routes Threatened
Very little is known about transient roosting sites used by the lesser long-nosed bat during migration. There is some speculation that roosts may be found in Nayarit and Sinaloa in Mexico but drug traffickers and the remoteness of the areas have prevented thorough surveys.
It is also possible that these very issues may also be protecting the lesser long-nosed bats by reducing other activities in the area. This is in contrast to some parts of Mexico which have seen serious losses of bat populations in efforts to reduce vampire bat (Desmodus rotundus) numbers.
Other threats along the bats’ migratory route include agricultural, recreational and urban development which encroaches on critical habitat. The popularity of the agave plant (Agave sp) in the food, tequila and decorative plant industries are posing another problem. Agave is often harvested before it has been allowed to bloom, meaning no nectar is available for the lesser long-nosed bats.
US Border Wall May Threaten Maternal Roosts in the United States
One of the largest populations of lesser long-nosed bats in the United States is found in the Cabeza Prieta Reserve. The construction and ongoing noise and light pollution from surveillance towers being placed in this reserve pose a serious threat to this bat colony.
Should the Lesser Long-Nosed Bat Be Listed Under the Endangered Species Act?
The finding of new colonies of lesser long-nosed bats was good news. Since then, however, several roosting sites have been abandoned, particularly along the border between the US and Mexico, where both the movement of illegal aliens and the increased US enforcement efforts have created disturbances.
The separation of the lesser long-nosed bats into two breeding populations reduces the chance of intermixing. The two populations must therefore be evaluated separately for risks. The numbers of bats in the southern population have little, if any, effect on the US population.
Because the lesser long-nosed bat is highly colonial any disruption at one of the major roosting sites could result in huge losses from a single incident. Anything from mining cave collapse to wildlfires could wipe out a critical roost and its inhabitants.
With only three known maternity roosts and three late summer roosts present in the US, a loss of any of these sites may have significant impact on the species. Thus, despite the increase in numbers of lesser long-nosed bats during recent surveys, the potential threats are significant and listing under the Endangered Species Act is justified.