Gray Bat

The gray bat (Myotis grisescens) is a medium-sized insectivorous bat with an overall length of about 3.5 inches and a wingspan of 10 to 11 inches. As the name implies, gray bats have gray fur, but the hair often bleaches to reddish-brown by early summer. The gray bat occurs in limestone karst areas, meaning a landscape marked by caves, sinkholes, springs and other features, of the southeastern and midwestern United States. It is estimated that more than 95% of the species range-wide population hibernate in only 15 caves. The gray bat was added to the U.S. List of Endangered and Threatened Wildlife and Plants on April 28, 1976.

Threats

At the time of listing, the main historical threats to the gray bat were human disturbance to roosting bats, environmental contamination, impoundment of waterways and roost modification or destruction. Such roost modifications include cave entrance or mine sealing and other modifications of the internal environment and entrances. The species is also negatively impacted by cave commercialization, improper gating and natural calamities, like cave-ins and flood events. Emerging threats, like interactions with wind turbines and climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change have been added as potential threats, since gray bats were first federally listed. 

Gray bats are particularly sensitive to human disturbance via cave entry and exploration. Unlike some Myotis species in the midwest and southeast, like the Indiana, northern long-eared and little brown bat species, that typically roost high up in dead-standing trees and out of reach of humans, gray bats roost on the ceilings of caves and rear young in places where humans can disturb them with their presence through physical touch, noise and artificial lighting. To help recover gray bat populations, the 1982 Gray Bat Recovery Plan primarily focused on developing a plan to permanently protect important summer and winter caves from human disturbance. As a result, many gray bat sites were permanently protected through long-term voluntary landowner agreements, like stewardship plans, conservation easements, habitat management plans or memorandum of agreements, that protect sites in perpetuity. Protections typically involve posting signage that asks people not to enter caves when bats could be present. These protection measures can also involve more extreme measures, like building permanent gate structures at the opening of the cave or installing fencing around a cave to prevent human entry. While limiting public access through the use of gating is sometimes unpopular with recreational caving communities and the wider public, it has led to a steady increase in recovery of many gray bat and other bat populations. Some populations that reside within unprotected sites continue to suffer from repeated human disturbance, but overall, the threat from human disturbance has been greatly reduced since the 1970s.  

Surveys conducted since 2009 indicate that gray bats do not appear to be susceptible to white-nose syndrome to the same degree as other affected Myotis. No mass mortalities have been documented, although to our knowledge, no studies have attempted to determine if sub-lethal impacts occur in gray bats as a result of white-nose syndrome. Based on the very few observed and confirmed white-nose syndrome affected gray bats and stable population numbers, gray bats appear to be resistant to the disease despite sharing hibernacula with other highly vulnerable species.

Efforts to prevent extinction?

Due to the diligent and hard work of many federal and state agencies and partners, 32 of 46, or 70%, of biologically significant summering roost sites across the gray bat’s range are considered permanently protected. Additionally, of the 15 major hibernacula, 14 are considered permanently protected. Thus, a significant proportion of the gray bat range-wide population is now protected from disturbance in its winter and summer habitat.  

It is not advisable to enter gated caves, mines or sites with a sign at the entrance which indicates it is used by endangered bats. These gates and signs are in place to protect bat colonies that are sensitive to human disturbance. Disturbance during the summer before the young can fly can result in thousands of flightless young becoming dislodged and falling to their deaths. Every arousal during hibernation is energetically expensive. Fat reserves required to sustain the bats are utilized to some extent during each winter arousal. Too many arousals during hibernation can exhaust a bat’s?limited energy reserves and cause them to starve. The best thing the public can do to help bats is to admire them from afar, when they can be seen flying across the sky at sunset.  

Conservation efforts also include protecting woodlands surrounding caves and wooded riparian riparian
Definition of riparian habitat or riparian areas.

Learn more about riparian corridors along streams near caves where gray bats forage. Removal of woodlands adjacent to water bodies and along riparian corridors may degrade and adversely affect gray bat foraging habitat.