Leptonycteris nivalis

Prior to 1962 (Davis and Carter 1962), specimens of Leptonycteris yerbabuenae were reported as L. nivalis.

Widely distributed but relatively rare in Mexico; also occurs in a few areas in southwestern Texas and southwestern New Mexico; recent population size and trend are not well documented; known primary threats include disturbance of cave roosts by humans and loss/degradation of foraging habitat/food resources (e.g., wild agave) as a result of human activities.

Range includes northern and central Mexico, southwestern Texas, and southwestern New Mexico, generally at elevations of about 500 to 3,000+ meters. Most occurrences in Mexico are at elevations of 1,000-2,200 meters, but this bat been captured at an elevation of 3,780 meters (see Arita 1991), and the type specimen reportedly was caught near snow line at 17,816 feet (5,747 meters) on Mt. Orizaba, in Veracruz, Mexico (USFWS 1994). In Texas, the species has been captured in Big Bend National Park (Brewster County) and the Chinati Mountains (Presidio County); Emory Peak Cave in the Chisos Mountains (elevation 2,290 meters) hosts the only known roosting population in Texas (Ammerman et al. 2012). Two specimens of Leptonycteris taken in Hidalgo County, New Mexico (in 1963 and 1967), were determined to be L. nivalis. The presence of this species in New Mexico was reconfirmed in Hidalgo County in 1992 (Hoyt et al. 1994). Populations exist in the Animas and Big Hatchet mountain in New Mexico (P. Cryan, pers. comm., cited by Ammerman et al. 2012). The range has been described as extending into Guatemala and adjacent southern Mexico (Hensley and Wilkins 1988; Simmons, in Wilson and Reeder 2005), but specimens collected from those areas were assigned to L. yerbabuenae by Arita and Humphrey (1988) and Arita (1991). Simmons (in Wilson and Reeder 2005) described the range of L. nivalis as including southeastern Arizona, but no actual records for Arizona are known.

The number of occurrences or subpopulations has not been determined using standardized/meaningful criteria; if based on regularly occupied roost sites, the number probably exceeds 20 and may not exceed 80. Arita and Humphrey (1988) and Arita (1991) mapped 43 confirmed collection sites for L. nivalis in Mexico, though not all of these necessarily represent roost sites. Just a few roosting sites exist in the United States, but there could be additional sites that have not yet been detected.

Primary threats include disturbance of roosts, loss of food sources through clearing of land for agriculture and human exploitation of agaves (e.g., for production of alcoholic beverages), and direct killing by humans (USFWS 1987, USFWS 1988, USFWS 1994). Other threats may include negative effects of ingestion of pesticides applied to plants, competition for roosts and nectar, natural catastrophes, disease, and predation; however, these are not believed to be major limiting factors, though some of them could become significant for populations reduced to small size by other factors (see USFWS 1994).

These bats are sensitive to disturbance in their roosting sites (they often quickly take flight upon human entry; Wilson 1985, Wilson et al. 1985) and, in general, roosting caves are becoming increasingly subject to human destruction and disturbance. Human disturbance and destruction of roost sites is a common occurrence in Mexico. The availability of roost sites free from disturbance may be a significant limiting factor.

A major problem for bats all over Mexico is that uninformed citizens frequently destroy all bats in a roost, believing them to be vampire bats (USFWS 1994).

The only known mating site for the species, Cueva del Diablo located in Tepoztlan, Morelos, Mexico, is threatened by residential development for tourism (Emma P. Gomez-Ruiz and Thomas E. Lacher, pers. comm., 2015).

Foraging habitat can be degraded or destroyed by harvesting of agave (an important food resource). It has been estimated that bootleg mescal makers are eliminating between 500,000 and 1,200,000 wild paniculate agave a year in Sonora alone. Agave plant parts are harvested just before they bloom; this prevents flowering and can prevent reproduction by the affected plant (an agave plant grows for 10 to 20 years, flowers only once, then dies). However, there are few places in Sonora or elsewhere in Mexico where wild Agave harvesting has eliminated a significant percentage of nectar-producing genets, and plants harvested by indigenous people generally produce vegetative offshoots that may eventually produce flowers (Nabhan and Fleming 1993). Populations of unharvested plants persist in many areas that are not easily accessible to humans. The negative impact of agave harvest probably is not as great as was previously believed. On the other hand, reduced pollination resulting from decreased bat populations may eventually lead to a reduction in agave distribution and abundance.

Preliminary data suggest that Agave is the main food source for L. nivalis in Coahuila and Nuevo Leon (Emma Gomez and Thomas Lacher, unpublished data). Human exploitation of wild agaves in the northern range needs to be evaluated to quantify this potential threat. Agaves are used extracting the nectar, and during intense drought periods the plants are harvested to feed cattle.

Some foraging habitat has been degraded or destroyed by expansion of agriculture and other land uses. Large areas of both the Sierra Madre Oriental and Sierra Madre Occidental and the Mexican Plateau have been converted to agriculture or rangeland.

Land clearing is a threat in northern Mexico, especially with recent plans for shale gas extraction and wind farm development (Emma P. Gomez-Ruiz and Thomas E. Lacher, pers. comm., 2015). Wind farming being developed in Coahuila and Nuevo Leon represents a risk, especially in areas where L. nivalis is known to occur during the summer migration. Evidence suggests that mainly pregnant females migrate to the North (maternity caves have only been reported in the North); wind turbine fatalities of pregnant females may pose a high risk to population stability (a better understanding of this risk is needed) (Emma P. Gomez-Ruiz and Thomas E. Lacher, pers. comm., 2015).

Changes in precipitation levels and timing have an effect on blooming events of Agave spp. (Emma P. Gomez-Ruiz and Thomas E. Lacher, pers. comm., 2015), so ongoing climate change potentially will affect this species.

This species may experience predation from owls, hawks, snakes, and mammals, but natural levels of predation likely are inconsequential to the overall status of the species. However, increased populations of domestic and feral cats and other predators near human habitations may affect the survival of colonies, particularly maternity colonies (USFWS 1994).