|Scientific Name:||Leptonycteris nivalis (Saussure, 1860)|
Ischnoglossa nivalis Saussure, 1860
|Taxonomic Notes:||Prior to 1962 specimens of Leptonycteris yerbabuenae were reported as L. nivalis. See Van Den Bussche (1992) for an analysis of phylogenetic relationships of phyllostomid bats based on restriction-site variation in the ribosomal-DNA gene complex.|
|Red List Category & Criteria:||Endangered A2c ver 3.1|
|Contributor(s):||Reid, F. & Arroyo-Cabrales, J.|
Greater Long-nosed Bat is widespread geographically, but the number of occurrences or subpopulations and population size have dramatically decreased in some sites. Several caves in central Mexico were known to contain considerable numbers in the past but now contain only small colonies or none at all, a similar situation occurs at the major colony in Texas (USFWS 2000). Major threats include disturbance of roosts (individuals often quickly take flight upon human entry, Wilson 1985), loss of food sources through clearing of land for agriculture and human exploitation of agaves. All these threats have proved to be significant factors in its decline. A population reduction is suspected to have been greater than 50% over the past three generations (15-18 years, Pacifici et al. 2013) as a direct result of local extinctions and habitat loss. More data and population monitoring are required for this species, and a reassessment is recommended as soon as additional information becomes available.
|Previously published Red List assessments:|
|Range Description:||This species is known from southeast Arizona, south New Mexico and southwest Texas (USA) to south Mexico and Guatemala (Simmons 2005). However, there is no evidence of this species being present south of Guerrero, Mexico (R. Medellín unpubl. data), and its southern limit of distribution should be adjusted to central Guerrero, Mexico, to reflect this fact. It generally occurs from lowlands to 3,500 m asl (mostly 1,000 to 2,200 m asl, Reid 1997).|
The range includes medium to high elevations in northern and central Mexico, southwestern Texas (southern Brewster and Presidio counties), and southwestern New Mexico, at elevations of about 500 to 3,500 m asl. Most occurrences in Mexico are at elevations of 1,000 to 2,200 m asl, but this bat been captured at an elevation of 3,780 m asl (Arita 1991), and the type specimen was caught near snow line at 17,816 feet (5,747 m asl) on Mt. Orizaba, in Veracruz, Mexico (USFWS 2000). In Texas, this species is known from the Big Bend National Park and Chinati Mountain area. 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). This species formerly was thought to occupy a much larger area, extending into southern Mexico and Guatemala, but specimens collected from those areas have been assigned to L. yerbabuenae (Arita and Humphrey 1988). The only colonial roost in the U.S. is a cave at Emory Peak, at an elevation of 2,290 m asl, in the Chisos Mountains, Texas. Simmons (2005) described the range of L. nivalis as extending to southern Mexico and Guatemala, and she also included southeastern Arizona in the range. However, no actual records for Arizona are known, and Arita (1991) showed the range as extending only as far south as Puebla and northern Guerrero.
Native:Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This bat is uncommon or rare (Reid 1997). The number of occurrences or subpopulations is unknown but probably exceeds 20; Arita (1991) mapped a few dozen collection sites in Mexico. One known colonial roosting site exists in the United States, which has shown large declines in the past (Matthews and Moseley 1990), but there could be one or more additional sites that have not yet been detected. The number of occurrences or subpopulations with good viability is unknown but likely there are not very many. Several caves in central Mexico were known to contain considerable numbers in the past but now contain only small colonies or none at all (see USFWS 2000). It is probably declining in number of occurrences or subpopulations and in overall population size, but the rate of decline is unknown and better information is need. The only mating roost has been declining but is now protected.|
There is a single known U.S. roost at Emory Peak (a cave in Big Bend National Park, Texas), which fluctuates widely from year to year (zero to 10,000+ individuals): 10,650 bats in 1967, 5,000 in 1968, 3,900 in 1969, zero in 1970, 8,025 in 1971, 1,000 in 1983, 4,942-5,990 in 1988, over 5,000 in 1991, zero in 1992, and 2,859 in 1993 (Matthews and Moseley 1990, see USFWS 2000). No significant trend can be ascertained from these data, which are the best available for the species. Reasons for the fluctuations are not understood, but they could reflect annual variations in food resources in different parts of the range (USFWS 2000). Fluctuation may be in part due to some counts being made before or after the main period of bat occupation of the cave (Cockrum and Petryszyn 1991). The Texas subpopulation may be a "spill-over" colony present during years of high population or reduced food supply.
Sánchez and Medellín (2007) estimated the colony at Cueva del Diablo, Morelos, central Mexico, at 3,000 individuals, while López (2010) estimated the same colony at 4,000. Both estimates were done visually under the supervision of the same individual (R. Medellin) and during the winter months, the only time of the year this species remains in the area. Arita and Prado rated this species as widespread and scarce in Mexico. See Arita (1993) for general information on conservation status and population size in Mexico.
The long-term trend is unclear. The extent of occurrence (EOO) and area of occupancy (AOO) probably have not changed much, but the habitat quality, the number of occurrences or subpopulations and population size may have dramatically decreased in some sites during the last three decades. Wilson et al. (1985) found that this species was either completely absent or present in reduced numbers in known roosts. The number of bats found represented only a fraction of the total reported in previous studies. For example, in an abandoned mine in Nuevo Leon, Mexico, where an estimated population of 10,000 was observed in 1938, no individuals of L. nivalis were found in 1983 (Wilson 1985). Another mine in Nuevo Leon had a ceiling covered with newborn bats in 1967, but only one bat was found in 1983. A few other roosts had reduced numbers of bats compared to findings during previous surveys. These changes could indicate a decline in the overall population, but they might reflect movement of bats among different roosting sites in different years, or they could result from seasonal changes in bat distribution (survey dates varied).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Habitats include desert scrub, open conifer-oak woodlands and pine forests in the Upper Sonoran and Transition Life Zones, generally arid areas where agave plants are present (USFWS 2000). This species usually favours higher and cooler regions than L. yerbabuenae (Arita 1991). Roosting habitat requirements are not well known. It usually roosts in large groups (up to 10,000) in caves or mines, occasionally found in buildings, hollow trees or culverts. It emerges well after sunset and feeds on pollen and nectar, principally of agaves and various cacti. Pseudobombax, Ceiba, Ipomoea, Calliandra, Pinus, and grasses are also important food sources in Central Mexico (Gardner 1977). Fruit and insects are sometimes taken; 173 samples contained insect parts in central México (Sánchez and Medellín 2007). Northern subpopulations migrate south in winter; numbers found in caves fluctuate greatly from year to year, indicating eruptive movements in addition to seasonal migration. A single young is born in May or June (Hensley and Wilkins 1988, Reid 1997).|
|Generation Length (years):||5-6|
|Use and Trade:||This species is not used.|
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. 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 subpopulations reduced to small size by other factors (see USFWS 2000).
These bats are sensitive to disturbance in their roosting sites (they often quickly take flight upon human entry; Wilson 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. Special precautions should be taken when mine and cave surveys are conducted. In June and July when the young are very small, disturbance can cause them to lose their grasp on the rock and fall to their death. During hibernation, disturbance will cause an increase in metabolism; this use of fat reserves may cause starvation prior to spring (New Mexico Department of Game and Fish 1996). 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.
Foraging habitat can be degraded or destroyed by harvesting of agave (an important food resource). Although it has been estimated that bootleg mescal makers are eliminating between 500,00 and 1,200,000 wild paniculate agave a year in Sonora alone, there is no clear support for such a statement. 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.
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.
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 2000).
|Conservation Actions:||A protected subpopulation exists at Emory Peak, Big Bend National Park, Texas (USFWS 2000). Further regular surveys are needed to determine important roost sites, abundance and trends. Conservation of this bat will require maintenance of relatively large areas of wild Agave. Identification and protection of currently and formerly occupied roost sites and protection of foraging habitat in at least several areas throughout the range are important conservation needs. Subpopulations need to be defined, and movement patterns need to be better understood. Accurate censusing methods need to be developed. This species is the focus of a specific conservation program by the government and the University of Mexico (UNAM). The only mating roost known in the state of Morelos, central Mexico is now secured as a sanctuary and with the aid of the local land owners the situation is improving dramatically. In Mexico the species is listed as threatened under NOM - 059 - SEMARNAT - 2015, and is a priority species of the Mexican Bat Conservation Program and of the Commission of Protected Areas of the Mexican Federal Government.|
|Citation:||Medellín, R. 2016. Leptonycteris nivalis. The IUCN Red List of Threatened Species 2016: e.T11697A22126172.Downloaded on 20 September 2018.|
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