Northern myotis (Myotis septentrionalis), also referred to as the northern long-eared bat, is one of three different species with a similar common name. Long-eared myotis (Myotis evotis) occur in western North America and brown long-eared bats (Plecotus auritus) occur in Europe. Records previously referring to Keen's myotis (Myotis keenii) in New York and eastern North America, are now known to be northern myotis which was first recognized as a distinct species, rather than a subspecies of Keen's Myotis, in 1979 (Van Zyll De Jong 1979).
Northern myotis were relatively common in New York prior to the first appearance of white-nose syndrome (WNS) in 2006. They have since declined dramatically with only an estimated 2% of the pre-WNS population numbers remaining in 2012 (NYSDEC 2012). The northern myotis is now one of the least commonly encountered species during winter hibernacula surveys (NYSDEC unpublished data).
Northern myotis have declined approximately 99% since white-nose syndrome began in New York in 2006 through 2015. Similar declines have occurred in the northeastern part of their range (Turner et al. 2011; U.S. Fish and Wildlife Service 2013). Numbers dropped from 911 to only 18 individuals counted among 36 hibernacula sites repeatedly surveyed from 2007-2012 (NYSDEC 2012). These numbers do not represent complete counts of the statewide population, however, since this species may roost individually and in crevices prohibiting a complete count of the remaining population.
The long-term trends were presumed to be stable or increasing prior to the appearance of white-nose syndrome in 2006 (C. Herzog pers. comm.).
The northern myotis is primarily associated with uplands and mature interior forests. Populations in New York and the eastern U.S. are threatened by white-nose syndrome. Due to the potential for continued rangewide declines from white-nose syndrome, the northern myotis has been listed as Threatened under the Endangered Species Act (U.S. Fish and Wildlife Service 2015). Other threats to this species include incompatible forest management practices, development, habitat fragmentation, and environmental toxins.
By far the largest threat to northern myotis in New York is white-nose syndrome (WNS) which was first discovered among bats in a cave in Schoharie County, New York in 2006. White-nose syndrome is caused by a fungus Pseudogymnoascus destructans (previously Geomyces destructans) that is often visible on the bats' muzzle and wings (Blehert et al. 2009). The fungus may invade hair follicles and cause lesions under the skin (Blehert et al. 2009). Bats wake from hibernation to groom and consequently burn fat reserves that are needed to survive the winter and they become emaciated (Blehert et al. 2009). Extensive damage to their wing membranes and dehydration may also be contributing factors to mortality (U.S. Fish and Wildlife Service 2013).
Some forest management practices may not be compatible with this species. Since northern myotis are adapted to exploit mature interior forest, harvests that remove significant canopy cover can reduce habitat for this species. The 90-day finding on the petition to list the northern myotis under the Endangered Species Act cited direct and indirect effects of logging as a threat to this species (U.S. Fish and Wildlife Service 2011). Direct mortality could occur when felled live trees contain colonies or roosting individuals and timber management may reduce or fragment the mature interior forest habitat required by this species. Similarly, development can also fragment forests making them unsuitable for this species.
Bats may be particularly sensitive to environmental toxins including those found in herbicides and pesticides. Although no studies have targeted northern myotis directly, elevated levels of persistent organic pollutants including especially PCBs, DDT, Chlordanes, and PBDEs have been found in a similar species, the little brown bat, in the Hudson River Valley in New York (Kannan et al. 2010). The levels found in the bats were only 1 to 3 times less than lethal concentrations reported from previous studies (Kannan et al. 2010). Lesser toxin levels may be expected in northern myotis since little brown bats typically consume a greater percentage of prey with an aquatic life stage. Bats are highly susceptible to DDT residue and this chemical was widely used as a pesticide to control bat infestations in houses in the 1940s (USGS 2013). It was widely used as an agricultural pesticide in the 1950s and 60s until its agricultural use was banned in 1972. Since DDT is highly persistent (soil half-life is 2-15 years, aquatic half-life is about 150 years) (NPIC 1999), it can pose a threat to bats when there is exposure to trace residues in the environment (USGS 2013). Extensive applications of insecticides and some bio control methods, such as Btk, could also pose an indirect risk to northern myotis by reducing availability of prey.
If proper precautions are not used, cavers and researchers entering hibernacula may cause disturbance that rouses bat colonies or transport the fungus that causes WNS on their clothing (NatureServe 2013). Other potential threats may include climate change, commercial cave development, flooding and hibernacula collapse; habitat loss and fragmentation from development, hydraulic fracturing, and construction of new wind facilities; and direct mortality from wind facilities (U.S. Fish and Wildlife Service 2013).
Gating mines and caves can prevent human entry while allowing the bats unobstructed access. Following proper specifications and monitoring bat populations before and after gate installation are important, however, as gating can affect the airflow and temperature in the cave, making areas of the cave uninhabitable for certain species (U.S. Fish and Wildlife Service 2013). Buildup of debris at cave entrance gates may have the same effect (U.S. Fish and Wildlife Service 2013). Retaining large trees and unfragmented blocks of late-seral stage forests of mixed age classes may be important for this species. Harvests that substantially reduce the forest canopy may not be compatible with habitat management for this species.
Retaining snags and dying trees can provide summer roosting habitat for northern myotis. Retaining overhead canopy, mature trees, and minimizing fragmentation of mature patches may also be important.
Research is needed to document summer roost locations in New York and to determine the extent of local populations. Ongoing winter hibernacula surveys are needed to monitor trends of the remaining populations.
Conservation needs have not yet been assessed for this species in New York. The current distribution of northern myotis in the state, as well as identification of summer locations with the highest local abundances are needed prior to determining specific management and conservation needs.
Northern myotis are typically associated with mature interior forest (Carroll et al. 2002) and tend to avoid woodlands with significant edge habitat (Yates and Muzika 2006). Northern myotis may most often be found in cluttered or densely forested areas including in uplands and at streams or vernal pools (Brooks and Ford 2005). Northern myotis may use small openings or canopy gaps as well. In one study in northwestern South Carolina, detection of northern myotis was best predicted in mature stands but also in areas with sparse vegetation (Loeb and O'Keefe 2006). Some research suggests that northern myotis forage on forested ridges and hillsides rather than in riparian or floodplain forests (Harvey et al. 1999). Captures from NY suggest that northern myotis may also be found using younger forest types (NYSDEC unpublished data). Northern myotis select day roosts in dead or live trees under loose bark, or in cavities and crevices, and may sometimes use caves as night roosts (U.S. Fish and Wildlife Service 2013). They may also roost in buildings or behind shutters. A variety of tree species are used for roosting. The structural complexity of surrounding habitat and availability of roost trees may be important factors in roost selection (Carter and Feldhamer 2005). Roosts of female bats tend to be large diameter, tall trees, and in at least some areas, located within a less dense canopy (Sasse and Pekins 1996). Northern myotis hibernates in caves and mines where the air temperature is constant, preferring cooler areas with high humidity (U.S. Fish and Wildlife Service 2013).
During summer the northern myotis occurs in a patchy distribution and may be found throughout most of the state including Long Island. It is unknown whether the statewide distribution has declined since WNS began. Winter surveys prior to the start of WNS had recorded this species in all regions of the state where mines and caves have been surveyed.
The northern Myotis is widespread throughout much of Canada and the eastern half of the United States. Prior to the onset of WNS it was more common in the northern parts of its range. Whether or not its distribution has changed since the start of WNS is unknown.
The northern myotis is a medium-sized brown bat with ears that when flattened extend at least 3 mm beyond the tip of its nose. It has a long pointed tragus. It weighs 6-9 g (0.2-0.3 oz) and has a wingspan of 23-26 cm (9-10 in). Its pelage is medium to dark brown on the back and gray to tawny brown underneath.
Northern myotis can be distinguished from other Myotis species by their longer ears, longer pointed tragus, larger wing area, and longer tail. They may also be distinguished acoustically, by analyzing echolocations recorded with a bat detector. Occasionally spectrograms, or visual representations of sound frequencies, of their echolocations could appear similar to some other Myotis species especially small-footed (M. leibii) and Indiana bats (M. sodalis) in the northeast.
Adults may be easiest to identify.
Northern myotis are nocturnal with periods of heightened activity at pre-dawn and dusk. They maintain large home ranges (although perhaps smaller than some other bat species) to meet their daily energy and resting needs. On study in West Virginia found mean home ranges among females to be 65 ha (range 18-98 ha) (Owen et al. 2003). Northern myotis may roost in small colonies or individually and they switch roosts often (Sasse and Pekins 1996; Carter and Feldhamer 2005).
Northern myotis are short-distance migrants. They have been documented traveling up to 168 miles from hibernacula to summer colonies (Griffin 1945). They have also been documented to move between hibernacula during the winter (U.S. Fish and Wildlife Service 2013).
Genetic research has indicated that there may be male-biased dispersal and site fidelity in females for this species as is common in mammals (Arnold 2007). This means that females often return to the same areas to raise pups and males travel farther than females to find mates. There also appear to be unbalanced sex ratios in favor of males in some regions (NatureServe 2013).
The northern myotis, like most bats, breeds in the fall; they swarm and mate near the cave entrance. Females store sperm over the winter until ovulation occurs in the spring which coincides with emergence from winter hibernacula. Females give birth to one young approximately 50-60 days later (Baker 1983).
Northern myotis obtain insect prey by capturing them out of the air (aerial hawking) and by gleaning them from vegetation. Locating insects by passive detection and gleaning may allow the northern myotis to obtain a wider variety of insect prey than is typically available to echolocating bats (Faure et al. 1993; Caceres and Barclay 2000). Northern myotis typically forage in forests under the canopy but above the understory, or in small openings, or along streams (U.S. Fish and Wildlife Service 2011).
Northern myotis have a varied diet. They appear to feed primarily on moths, beetles, and flies although other insect orders are consumed as well, and there are regional differences in major prey items. The diet of northern myotis consisted primarily of beetles (Coleoptera 42%) and moths (Lepidoptera 31%) in one study in West Virginia (Carter et al. 2003). Moths (49%) and beetles (38%) were also the primary prey species found in a larger study in the central Appalachians, with lesser amounts of flies (Diptera) and true bugs (Hemiptera) consumed as well (Dodd et al. 2012). In Indiana, northern myotis preyed primarily on flies (38%) but also beetles (25%) and moths (21%) (Whitaker 2004). Dodd et al. (2012) found that overall, 55% of prey was classified as microlepidoptera, indicating the value of tiny often overlooked moths to this species. Data concerning prey selection are not available specifically for New York.
Northern myotis are active at dusk during the spring and summer but they are difficult to distinguish from other Myotis species in flight.
The time of year you would expect to find Northern Long-eared Bat present, active, and reproducing in New York.
Northern Long-eared Bat
Myotis septentrionalis (Trovessart, 1897)
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Sasse, D. B. and P. J. Pekins. 1996. Summer roosting ecology of northern long-eared bats (Myotis septentrionalis) in the White Mountain National Forest. Pp. 91-101 in Proceedings of the Bats and Forests Symposium of the British Columbia Ministry of Forests, Victoria, BC, Canada.
Turner, G. G., D. Reeder and J. T. Coleman. 2011. A Five-year Assessment of Mortality and Geographic Spread of White-Nose Syndrome in North American Bats, with a Look at the Future. Update of White-Nose Syndrome in Bats. Bat Research News 52:13-27.
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Yates, M. and R. Muzika. 2006. Effect of forest structure and fragmentation on site occupancy of bat species in Missouri Ozark forests. Journal of Wildlife Management 70:1238-1248.
This guide was authored by: Kelly A. Perkins
Information for this guide was last updated on: March 8, 2019
Please cite this page as:
New York Natural Heritage Program. 2021. Online Conservation Guide for Myotis septentrionalis. Available from: https://guides.nynhp.org/northern-long-eared-bat/. Accessed September 24, 2021.