Northern Long-Eared Bat

The U.S. Fish and Wildlife Service (USFWS) published a final rule reclassifying the northern long-eared bat (Myotis septentrionalis) from threatened to endangered under the Endangered Species Act. The rule took effect on March 31, 2023. The northern long-eared bat is known to occur throughout much of New York State, including Oyster Bay in Nassau County and the entirety of Suffolk County. As per the Final Rule, the USFWS is committed to reducing the impacts of disease and protecting the survivors to recover the population. Because of the importance of the Long Island sub-population, the NYS Department of Conservation is currently developing region-specific guidance.

The northern long-eared bat is about 3 to 3.7 inches long with a wingspan of 9 to 10 inches. It is distinguished by its long ears, particularly compared to other bats in its genus, Myotis. It emerges at dusk to fly primarily through the understory of forest areas, feeding mostly on moths, flies, leafhoppers, caddisflies and beetles. It catches these insects while in flight using echolocation or by using gleaning behavior, catching motionless insects from vegetation.

Long Island’s northern long-eared bat population is considered one of a few source sub-populations to one day replenish the species throughout its native range (“Bats Prove a Bellwether for a Changing Habitat Paradigm” East End Beacon July 2023 | Vol 7 Issue 7). The main threat to northern long-eared bat is white-nose syndrome (a disease caused by a fungal pathogen) and has caused a precipitous decline in bat numbers (in many cases, 90-100 percent) where the disease has occurred (81FR1900 Endangered and Threatened Wildlife and Plants; 4(d) Rule for the Northern Long-Eared Bat published on 1/14/2016) . Declines in the numbers of northern long-eared bats are expected to continue as WNS extends across the species’ range. Because Long Island lacks caves and the bats have adapted by not hibernating in large numbers, Long Island is one of the few places in which the northern long-eared bat population is more robust. Researchers from SUNY Albany have found that the bats on eastern Long Island hibernate in small groupings of five to six, instead of groups of hundreds, so the fungus is less easily transmitted (“Bats Prove a Bellwether for a Changing Habitat Paradigm” East End Beacon July 2023 | Vol 7 Issue 7). Small groups of hibernating bats are also more likely to find insects to feed on if they awaken during hibernation.

Wind energy mortality, effects from climate change, and habitat loss also influence the northern long-eared bat’s viability. As per the USFWS Species Status Report (2022), “Habitat loss may include loss of suitable roosting or foraging habitat, resulting in longer flights between suitable roosting and foraging habitats due to habitat fragmentation, fragmentation of maternity colony networks, and direct injury or mortality.” The northern long-eared bat is assumed to be present in any forested habitat in Suffolk County (meaning a land owner cannot prove absence). According to biologists, the northern long-eared bat seeks out trees with cracks and crevices (i.e., black locust, shagbark hickory, and old oaks) for day roosting, and any trees with snags or cavities for maternity roosts. Given the low reproductive potential of northern long-eared bats (one pup per female per year), death of adult females or pups during tree felling (or erasing their habitat altogether with a large housing or commercial development) will continue to erode the long-term viability of Long Island’s sub-population.

Artificial lighting results in the loss of habitat for the northern long-eared bat. “Installation of temporary or permanent lighting can introduce barriers to movement, sever foraging areas, discourage emergence or precipitate roost abandonment. Roost adjacent lighting may modify microclimatic conditions (i.e., humidity or temperature) or cause disturbance, which may precipitate roost abandonment.” (White-nose Syndrome Conservation and Recovery Working Group 2018).

The report Use of Forested Habitat Adjacent to Highways by Northern Long-Eared Bats (Foster et al. 2019) prepared for The New England Transportation Consortium further outlines how artificial light reduces the habitat of the northern long-eared bat (NLEB): 
“Artificial light can affect roosting and foraging behavior. Bats will delay leaving roosts that are near lights (Downs et al. 2003), which reduces foraging opportunities (Jones and Rydell 1994). Light near roosts also leads to lighter and smaller juvenile bats due to delayed parturition and slower growth rates (Boldogh et al. 2007). Road lighting deters slow-flying, forested-adapted species such as NLEB (Rydell 1992, Blake et al. 1994, Stone et al. 2009). Older sodium lights and new LED lights deter forest species even at low light intensities (>3.6 lux) (Stone et al. 2012). Bats will reverse flight direction when they perceive low intensity light sources (0.6–3.2 lux) (Kuijper et al. 2008). Street lights are usually between 10–60 lux (Gaston et al. 2012), thus dimming lights to acceptable levels for bats may not be feasible. Open space foraging bats can benefit from lights with improved foraging efficiency, as insects exhibit positive phototaxis resulting in higher insect abundances around light sources (Rydell 1992, Blake et al. 1994). However, this concentrating effect on insects reduces insect prey in dark foraging areas thus decreasing prey abundance and foraging success for light phobic genera such as Myotis spp. (Eisenbeis 2006, Evens 2012). While the effects of lights on Northern Long-Eared Bat (NLEB) have not been directly assessed, NLEB is a forest-dependent species (light adverse) whose primary prey, moths, are highly phototaxic, thus it stands to reason that NLEB foraging success may be greatly reduced in lighted landscapes.” (page 7)

Blake, D., Hutson, A. M., Racey, P. A., Rydell, J., & Speakman, J. R. (1994). Use of lamplit roads by foraging bats in southern England. Journal of Zoology, 234(3), 453-462.

Boldogh, S., Dobrosi, D., & Samu, P. (2007). The effects of the illumination of buildings on house-dwelling bats and its conservation consequences. Acta Chiropterologica, 9(2), 527- 534.

Downs, N. C., Beaton, V., Guest, J., Polanski, J., Robinson, S. L., & Racey, P. A. (2003). The effects of illuminating the roost entrance on the emergence behaviour of Pipistrellus pygmaeus. Biological Conservation, 111(2), 247–252. 3207(02)00298-7

Eisenbeis, G. 2006. Artificial night lighting and insects: attraction of insects to streetlamps in a rural setting in Germany. In Rich, C. and Longcore, T. eds Ecological consequences of artificial night lighting: 345–364. Washington, Island Press.

Evens, N. 2012. Shedding light on bat activity: artificial lighting has species-specific effects on British bats. Doctoral dissertation.

Foster, Jeffrey, et al. Use of Forested Habitat Adjacent to Highways by Northern Long-Eared Bats (and other Bats). No. NETC 15-1, NETCR117. New England Transportation Consortium, 2019.

Gaston, K. J., Davies, T. W., Bennie, J., & Hopkins, J. (2012). Reducing the ecological consequences of night‐time light pollution: options and developments. Journal of Applied Ecology, 49(6), 1256-1266. Jones, G., & Rydell, J. (1994). Foraging strategy and predation risk as factors influencing emergence time in echolocating bats. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 346(1318), 445-455.

Kuijper, D. P., Schut, J., van Dullemen, D., Toorman, H., Goossens, N., Ouwehand, J., & Limpens, H. J. G. A. (2008). Experimental evidence of light disturbance along the commuting routes of pond bats (Myotis dasycneme). Lutra, 51(1), 37.

Rydell, J. (1992). Exploitation of insects around streetlamps by bats in Sweden. Functional Ecology, 744-750.

Stone, E. L., Jones, G., & Harris, S. (2009). Street lighting disturbs commuting bats. Current Biology, 19(13), 1123–1127.

Stone, E. L., Jones, G., & Harris, S. (2012). Conserving energy at a cost to biodiversity? Impacts of LED lighting on bats. Global Change Biology, 18(8), 2458–2465.

U.S. Fish and Wildlife Service. 2022. Species Status Assessment Report for the Northern longeared bat (Myotis septentrionalis), Version 1.2. August 2022. Bloomington, MN.

White-nose Syndrome Conservation and Recovery Working Group, 2018. Acceptable Management Practices for Bat Species Inhabiting Transportation Infrastructure. A product of the White-nose Syndrome National Plan ( 49 pp.