In Big Bend National Park, Texas, the summer population of L. nivalis is smaller than it used to be. A similar trend is occurring in Arizona, where L. sanborni no longer occupies many of the caves that formerly held colonies. In central Mexico there are still large populations of L. sanborni , but L. nivalis never was abundant and no large colonies are known. Furthermore, several caves known to house considerable numbers of these bats in the past now contain only small colonies or lack bats altogether. Unfortunately, it is not often easy to assess the causes of vulnerability of certain species, especially for secretive animals like bats.
Habitat destruction is likely the major factor affecting long-nosed bats.
They are specialized nectar feeders and disappearance of their food plants could explain the decline in their populations. The fragility of the mutualistic relationships is magnified in the case of the long-nosed bats because of their migratory habits. These bats depend not only on the plants in a given region, but on a continuous supply of food along their migratory routes. Pesticides frequently are cited as a major threat to bats, but they are unlikely to seriously threaten nectar-feeding species. A possibility that has not been evaluated is that local cattlemen, in a misguided attempt to control numbers of vampire bats in Mexico, have destroyed colonies of cave-dwelling bats indiscriminately.