|Scientific Name:||Myotis leibii|
|Species Authority:||(Audubon & Bachman, 1842)|
|Taxonomic Notes:||Formerly, M. ciliolabrum was included as a subspecies of M. leibii (or M. subulatus). Based chiefly on cranial measurements, van Zyll de Jong (1985) recognized western populations of what had been known as M. subulatus as a species (M. ciliolabrum) distinct from eastern populations, for which the appropriate name is M. leibii. Electrophoretic data support the conclusion that the two taxa are specifically distinct (Herd 1987). Wilson and Ruff (1999) regarded M. ciliolabrum and M. leibii as separate species. Koopman (1993) did not recognize M. ciliolabrum as a species distinct from M. leibii, but Simmons (2005) did. Monotypic (Best and Jennings 1997).
In a phylogenetic study based on mtDNA data, M. leibii was included within clades containing both M. californicus and M. ciliolabrum (Rodriguez and Ammerman 2004). Further data from M. leibii are necessary to validate its phylogenetic relationship to M. ciliolabrum and M. californicus (Rodriguez and Ammerman 2004). Comparisons among outgroups (M. yumanensis, M. lucifugus, and M. evotis) found sufficient support for specific status of M. leibii, but sequence divergence between M. evotis and the leibii group was small (2.9%) and within the intraspecific range. Further sampling of M. evotis is necessary to establish the level of divergence between M. evotis, as well as other long-eared Myotis, and the leibii group (Rodriguez and Ammerman 2004).
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Arroyo-Cabrales, J. & Álvarez-Castañeda, S.T.|
|Reviewer(s):||Medellín, R. & Schipper, J.|
This species is listed as Least Concern in view of its wide distribution, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.
|Range Description:||The range extends from New England, southeastern Ontario, and southwestern Quebec south and west to southeastern Oklahoma, Arkansas, northern Alabama, northern Georgia, and northwestern South Carolina (Menzel et al. 2003). Within this range, the distribution is very spotty, and the bulk of the occurrences and largest populations are in New York, Pennsylvania, West Virginia, and western Virginia. Hall's (1981) map should be taken as potential range; there are no records of this species ever occurring in some parts of the indicated distribution (e.g., Illinois; Jim Herkert pers. comm.). This species is apparently extirpated in Connecticut and Ohio (where known from only one specimen). Elevational range extends to at least 700-800 meters in several states and to at least 1,125 meters in Kentucky (Best and Jennings 1997).|
Native:Canada (Ontario, Québec); United States (Alabama, Arizona, Connecticut, Delaware, Georgia, Kentucky, Maine, Maryland, Massachusetts, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, West Virginia)
|Range Map:||Click here to open the map viewer and explore range.|
Approximately 80% of the known occurrences are of poor estimated viability; just 7% are believed to have good or excellent viability. In most instances, surveys yield very few individuals of this species in any particular location.
Most occurrences have been counted only within the past decade or two and are not revisited regularly, making the assessment of population trend difficult. Many biologists believe that this species is basically stable, having declined little in recent times, but that it is vulnerable, especially in its cave hibernacula. The population at one site in Arkansas has increased in recent years, probably due to reduced winter disturbance following the installation of a cave gate.
|Habitat and Ecology:||
This species is most often detected during hibernation. In recent years, it has been counted at approximately 125 hibernacula. Recent surveys have greatly increased the number of localities above those known historically; the number of hibernacula may be significantly larger than currently known. Intensive cave and mine surveys have been undertaken in most states where the species occurs, but some sites probably remain unsearched in most states.
The total count for all hibernacula is approximately 3,000 individuals, with roughly 60% of the total number from just two sites in New York. Some of the occurrences probably have not been surveyed completely, and some individuals are undoubtedly missed within some sites because they are hibernating in portions of mines or caves that cannot be reached or easily observed.
This bat always has been considered to be relatively rare (Barbour and Davis 1969). Numbers are reduced in a few sites where older counts are available, and a few historical sites are apparently no longer occupied, but whether these observation reflect declines or changes in distribution is unknown. In Vermont, Myotis leibii has been consistently found in very small numbers and often not detected at all during periodic surveys of various hibernacula dating back to 1934 (Trombulak et al. 2001).
Habitat is mostly hilly or mountainous areas, in or near deciduous or evergreen forest, sometimes in mostly open farmland. In Pennsylvania, Mohr (1976) found this species mostly in heavy hemlock forests in the foothills of mountains that rise to 2,000 feet (600 meters). Unpublished data from the Kentucky Heritage Program indicate that summer roosts include caves, coal mines, buildings, and bridges over rivers (in expansion joints). Warm-season roosts include buildings, towers, hollow trees, spaces beneath the loose bark of trees, cliff crevices, and bridges. Tuttle (1964) reported two individuals found in April in Tennessee under a large flat rock at the edge of a quarry surrounded by woods and cow pastures. In Ontario, about 12 of these bats were found in July behind the door of a shed that was kept open (i.e., positioned against the wall) (Hitchcock 1955). They have been seen resting in limestone caves in West Virginia in spring and summer (Krutzsch 1966).
By far most records come from observations of bats hibernating in winter in caves and mine tunnels. Hibernation occurs in solution and fissure caves and mine tunnels (including coal, iron, copper, and talc mines). Situations near the entrance where the air is relatively cold and dry seem to be preferred (Barbour and Davis 1969), though sometimes deeper locations are used (Schwartz and Schwartz 1981). Roost sites often are deep in crevices, or under rocks on the cave floor, where the bats can be very difficult to find (Davis 1955, Krutzsch 1966, Martin et al. 1966). These bats are usually found singly or occasionally in small clusters, but many may be packed in a crevice; often they hang among other species (Marin et al. 1966). In tight places the body may be horizontal, even belly down. On cave walls, the forearms are somewhat extended rather than parallel to the body axis. Dunn and Hall (1989) noted that 52% of Pennsylvania hibernacula were small caves of less than 150 m (500 feet) in length. Like many other bat species, this one typically forages over ponds and streams.
Some mines may be threatened by closure or collapse. Ceiling collapse may kill bats outright or, more significantly, alter cave microhabitat enough to make it unsuitable. A few cave occurrences are threatened or have been reduced in quality due to commercialization for tourism.
Threats to summer sites are unknown, but are likely to be moderate due to alteration of riparian habitats. Conversion of forested habitats to agricultural and residential uses has decreased the amount of preferred habitat in some areas, but the bats do make use of bridges and various other non-natural roost sites.
Improper gating of caves to protect bats may result in site abandonment. For example, the large colony of M. leibii at Fourth Chute Cave, Quebec, was driven out by blocking the flow of cold air (Mohr 1976). In contrast, gating of cave entrances in other locations (e.g., Aitkin Cave, Pennsylvania) has led to increases in M. leibii populations. With its small numbers and spotty distribution, isolated colonies of M. leibii are particularly vulnerable to extirpation by chance events, especially when concentrated during winter months. On the other hand, in contrast to certain other bats that assemble in vast numbers in relatively few sites, the population of M. leibii as a whole is not vulnerable to localized events.
This bat tends to hibernate near cave entrances; hence it may be vulnerable to freezing in abnormally severe winters. THREATS TO BATS IN GENERAL: Perhaps the most serious threat to cave-dwelling bats is human disturbance during hibernation. Very low levels of noise, light, and heat from lanterns are sufficient to awaken hibernating bats, which then expend energy moving about and deplete critical reserves of body fat. When disturbance is repeated, bats (especially juveniles) are likely to perish. "By the end of the winter energy reserves may be insufficient to meet the demands of the first feeding forays, when emerging insects may be scattered and scarce, or the bats may be too weak to make long flights to their summer territories" (Mohr 1976). Such disturbance is equally lethal, whether caused by vandals, well-meaning spelunkers, or bat researchers. Intentional killing of bats in caves by clubbing, stoning, burning, bombing, etc. has been a significant cause of mortality. Documented examples are numerous (e.g. Tuttle 1979). Bats are sometimes exterminated from commercial caves, or if not, leave or move to suboptimal habitats due to increased disturbance. Poisoning by pesticides, heavy metals, and other environmental contaminants has been and may remain a significant threat. Destruction of roost and foraging habitat by reservoir inundation, strip mining (especially limestone), deforestation, drainage of wetlands, development, etc., and pollution or siltation of waterways with consequent decline in insect production are additional potential adverse impacts (Tuttle 1979). Hundreds of thousands of bats have been destroyed by natural flooding of caves.
There is a strong conservation easement held by The Nature Conservancy (TNC) on the second largest occurrence. TNC has a management agreement giving limited protection to the largest occurrence and one occurrence with apparently good viability is on National Park Service land in Arkansas. Several occurrences with fair to poor estimated viability in various states are either owned by TNC or are on Federal land.
Summer surveys throughout the species known range should be a high priority for inventory work. Winter hibernacula surveys should continue with emphasis on searching sites which have not been surveyed, improving counts in sites which have not been completely or thoroughly surveyed, and monitoring some portion of the known sites on a regular basis (perhaps every other year as recommended for Myotis sodalis sites) to establish baseline population trend data.
|Citation:||Arroyo-Cabrales, J. & Álvarez-Castañeda, S.T. 2008. Myotis leibii. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 28 August 2015.|
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