Myotis grisescens is widely distributed in the southeastern United States of America. The distribution of gray bats within their range has always been patchy. Gray bats inhabit the cave regions of northern Arkansas, Missouri, Kentucky, Tennessee, and Alabama. There are also occasional colonies in northwestern Florida, western Georgia, southwestern Kansas, southern Indiana, southern and southwestern Illinois, northeastern Oklahoma, northeastern Mississippi, western Virginia, and possibly western North Carolina.

Biogeographic Regions: nearctic (Native )

endemic to a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range extends from southeastern Kansas and central Oklahoma east to western Virginia and western North Carolina, and from Missouri, Illinois, and Indiana south to southern Alabama and northwestern Florida (Decher and Choate 1995); occurs primarily in the cave region of Missouri, Arkansas, Kentucky, Tennessee, and Alabama. Summer and winter ranges are essentially the same.

M. grisecens is the largest member of its genus in the eastern United States. They weigh between 7 and 16 g and are 75 to 101 mm in length. Forearm length ranges between 40 and 46 mm. Gray bats can be distinguished from all other eastern bats by their uni-colored dorsal fur (all others have bi- or tri-colored dorsal fur). They are also the only species of Myotis in which the wing membrane connects to the foot at the ankle as opposed to connecting at the base of the first toe.

Gray bats are dark gray in color directly after they molt in July or August. Between molts, they bleach to a russet color. This difference in fur color is most apparent in females during the reproductive season (May or June).

Range mass: 7 to 16 g.

Range length: 75 to 101 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Length: 10 cm

Weight: 9 grams

Most likely to be confused with M. lucifugus, M. sodalis, M. austroriparius, and M. septentrionalis. Distinguished from these by uniform-colored dorsal fur from base to tip (all others have contrasting shades, bi- or tri-colored dorsal fur) and by attachment of wing membrane at ankle, not at base of toe (Barbour and Davis 1969, Tuttle 1978).

• Terrestrial

Gray bats are restricted entirely to areas with caves or cave-like habitats. These caves are in limestone karst areas of the southeastern United States. Gray bats do not inhabit barns or other similar structures. This leads to extremely restricted nesting opportunities. Due to their requirement of unique cave types, Gray bats can only use 0.1% of available caves in the winter and 2.4% in the summer.

Ninety-five percent of the total Gray bat population hibernates in only eight or nine caves. Two are located in Tennessee, three in Missouri, one in Kentucky, one in Alabama, and one in Arkansas. The Arkansas hibernation cave houses about 250,000 Gray bats. The winter caves utilized by Gray bats have deep, vertical passages with large rooms that function as cold air traps. The temperature of these caves ranges between 6 and 11 degrees Celsius (42 and 52 degrees Fahrenheit).

As they are for the winter sites, gray bats are highly selective for caves providing specific temperature and roost conditions in the summer. These caves are warm, ranging between 14 and 25 degrees Celsius (57 and 77 degrees Fahrenheit). As an alternative to finding a cave within this temperature range, they can roost in caves with small rooms or dorms that trap the body heat of the roosting bats. Summer colonies of gray bats occupy a home range that often contains several roosting caves scattered along as much as 81 kilometers of river or lake shore. Banding studies have indicated that gray bats prefer summer caves that have a feeding area (river or other reservoir of water) not over 2 kilometers away. Despite this, they have been known to fly as far as 19 kilometers from the colony to feed.

Habitat Regions: temperate ; terrestrial

Other Habitat Features: riparian

Comments: Roost sites are nearly exclusively restricted to caves throughout the year (Hall and Wilson 1966, Barbour and Davis 1969, Tuttle 1976), though only a few percent of available caves are suitable (Tuttle 1979). Winter roosts are in deep vertical caves with domed halls. Large summer colonies utilize caves that trap warm air and provide restricted rooms or domed ceilings; maternity caves often have a stream flowing through them and are separate from the caves used in summer by males.

Occasionally non-cave roost sites are used. Hays and Bingman (1964) reported a colony in a storm sewer in Pittsburg, Kansas and, in 1988, a maternity colony was discovered using a storm sewer in Kansas (Decher and Choate 1988). Harvey and McDaniel (1988) located a maternity colony in a storm sewer in downtown Newark, Independence County, Arkansas. There are occasional reports of mines (Sealander 1979, Thom 1981, Brack et al. 1984, Harvey 1988) and buildings (Gunier and Elder 1971) being used as roost sites.

Winter caves are deep and vertical and provide a large volume of air below the lowest entrance that acts as a cold air trap (Tuttle 1976). Cold air flows in and is trapped during successive winters, providing mean annual temperatures 6 degrees C or more below the above-ground mean annual temperature (Tuttle 1978). Winter cave temperatures range from 6 to 11 degrees C (Tuttle 1979).

In the summer, maternity colonies prefer caves that act as warm air traps or that provide restricted rooms or domed ceilings that are capable of trapping the combined body heat from thousands of clustered individuals (Tuttle 1975, Tuttle and Stevenson 1977). Cave temperatures range from 14 to 24 C. Undisturbed summer colonies may contain up to 250,000 bats, and average 10,000 to 25,000 (Tuttle 1979). Summer caves are nearly always located within 1 km of a river or reservoir over which the bats forage (Tuttle 1979).

Tuttle (1979) showed that forested areas along the banks of streams and lakes provide important protection for adults and young. Young often feed and take shelter in forest areas near the entrance to cave roosts (Tuttle 1979). Do not feed in areas along rivers or reservoirs where the forest has been cleared (LaVal et al. 1977; Tuttle and Stevenson, in prep.).

Yearlings and adult males segregate into nomadic summer colonies that tend to roost in caves within a few kilometers of ones selected by adult females (Layne 1978).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Wintering caves often are hundreds of kilometers from summer range; Tuttle (1976) reported one-way migration distances of 17-525 kilometers. In some areas the same caves are used in winter and summer; in other areas (e.g., Missouri, Arkansas) many caves used in summer are vacant in winter. Most Florida breeders migrate north to hibernate in cooler caves of northern Alabama and central Tennessee; migration occurs mostly in September-October, some as late as November or December (Layne 1978), females preceding males. Females depart wintering caves in late March and early April, males in late April and May. Evidence suggests that bats migrate in small flocks (Barbour and Davis 1969). Small caves may be used as rest stops (Smith and Parmalee 1954).

M. grisescens forages over streams and reservoirs where they consume night-flying aquatic insects. Like all microchiropterans, gray bats rely on echolocation to locate their food.

Most foraging occurs within 5 meters of the water surface over which they are feeding.

Until most recently, studies focusing on the diet of gray bats were not preformed. Data on this subject are therefore preliminary. Whether gray bats are opportunistic or selective feeders is still in debate. Recent studies suggest that this species feeds selectively, but more information is needed.

Originally it was thought that gray bats fed primarily on mayflies. M. grisescens has been seen feeding in large swarms of mayflies, but this insect has not been turning up in fecal analysis in the proportion that might have been expected. It is possible that mayflies are wholly digested, thus not often seen in the fecal records.

Analysis of gray bat feces has shown that thes bats most often select moths, flies, and beetles as prey when these species are present.

Other prey includes spiders, bugs, leafhoppers, scorpionflies, lacewings, dragonflies, stoneflies, grasshoppers, thrips and wasps. Various insects occur sporadically in fecal pellet analysis.

Animal Foods: insects; terrestrial non-insect arthropods

Primary Diet: carnivore (Insectivore )

Comments: Feeds mostly upon flying insects, including mayflies (Choroterpes spp., STENOCRON spp.) and beetles (Tuttle et al., Lacki et al. 1995); diet may vary with local resources and habitat.

Foraging is generally parallel to streams, over the water at heights of 2 to 3 m (LaVal et al. 1977). Caire et al. (1989) stated that this bats is apparently adapted to forest foraging and rarely is collected in the open or over streams; geographic variation? The energy demands on adult females are tremendous during lactation, and individual females sometimes feed continuously for seven or more hours per night (Tuttle and Stevenson).

One bat can catch up to 3,000 insects in one night. Because of this, they play an important role in the checks and balances of nature as the primary controllers of night-flying aquatic insects.

Gray bats may fall prey to howks, owls, skunks, foxes, mice, snakes, and housecats. Anti-predator adaptations include avoiding crowded cave entrances and flying more rapidly when exiting and entering the cave.

Known Predators:

• hawks (Accipitridae)
• owls (Strigiformes)
• snakes (Serpentes)
• domestic cats (Felis silvestris)
• mice (Myomorpha)
• skunks (Mephitinae)
• swift foxes (Vulpes velox)
• gray foxes (Urocyon cinereoargenteus)
• red foxes (Vulpes vulpes)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 6 - 20

Comments: About 95% of entire known population hibernates in eight or nine caves, over half in one cave.

>1,000,000 individuals

Comments: Total population was estimated at 1.5 million in the early 1980s. About 10,000 are thought to occur in Florida in summer, a few hundred in winter (Wenner, Gore, cited by Humphrey 1992). Five gated maternity caves in Oklahoma each include 10,000 or 20,000 bats (Hensley 2003).

Forage in loose groups, but become territorial when insect numbers decrease; territories seem to be controlled by reproductively-active females (Tuttle et al.).

Each summer colony occupies a traditional home range that often contains several roosting caves scattered along as much as 70 kilometers of river or reservoir borders. Individuals forage along rivers or shoreline up to 20 km from their roosts (LaVal et al. 1977, Tuttle and Stevenson 1977).

Elder and Gunier (1981) determined that the mean annual survival rate is about 70% in males and 73% in females. Stevenson and Tuttle (1981) found that the after-first-year survival rate is about 55 to 85% in relatively undisturbed colonies, and 57 to 66% in disturbed colonies. The oldest bat recovered was about 16 years old, but Stevenson and Tuttle (1981) believe that maximum longevity could be 39 years. Mortality is especially high in spring migration when fat reserves and food supply are low (Tuttle and Stevenson 1977).

As in all mammals, there are a variety of means of communication. Bats use vocalizations to communicate with each other while they are in their roosts. Mothers and infants use tactile and vocal communication. There are probably some scent cues which help mothers to recognize their young.

Echolocation is used primarily to locate food. However, communication also occurs between predator and prey through echolocation. Some insects (particularly moths) can receive the sonar pulses from the bats and fly erratically to avoid being eaten.

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; acoustic ; echolocation

Comments: Females enter hibernation in fall after mating, followed by males and juveniles several weeks later (most females are hibernating by early October, most others are in hibernatation by early November). Adult females emerge from hibernation late March-early April. Others emerge mid-April to mid-May (Tuttle 1976). Forages at night.

After entering the winter cave, female Gray Bats are inseminated by sexually active male bats. The females exhibit delayed fertilization. After copulating, the females hold the sperm through hibernation. Fertilization between the sperm and ova occurs when the female emerges from hibernation. Females do not reach sexual maturity until they are two years old. For their size, bats are among the world’s slowest reproducing mammal.

 One offspring per sexually mature female is born in June when the colonies have migrated to their summer ranges. The period between birth and weaning is two months. During these two months there is segregation between members of the colony. The adult females and their newborns roost in maternity caves. The adult males and yearlings of both sexes roost in bachelor caves. By August, all the juveniles are flying (most are capable of flight 20-25 days after birth) and general mixing and dispersal of the colony occurs over the summer range. The growth rates of young vary with the temperature at the maternity roosts. It has been discovered that young in warmer roost situations grow more rapidly. (U.S. Fish and Wildlife Service, 1992; U.S. Fish and Wildlife Service Division of Endangered Species, 1991)

Development - Life Cycle: colonial growth

The maximum lifespan for gray bats is 14-15 years.

Typical lifespan

Status: wild: 14 to 15 years.

Information on the mating system of these animals is sparse. They are reportedly polygynous.

Mating System: polygynous

Breeding in this species occurs shortly after the bats enter their hiberation caves. After entering the winter cave, the female gray bat is inseminated. Females exhibit delayed fertilization. After copulating, a female holds the sperm through hibernation. Fertilization of ova occurs when the female emerges from hibernation.

Females do not reach sexual maturity until they are two years old. For their size, bats are among the world’s slowest reproducing mammal.

Females give birth to a single offspring in June, after migration to the summer caves has taken place. The period between birth and weaning is two months. During these two months there is segregation between members of the colony. The adult females and their newborns roost in maternity caves. The adult males and yearlings of both sexes roost in bachelor caves.

By August, all the juveniles are flying (most are capable of flight 20-25 days after birth) and general mixing and dispersal of the colony occurs over the summer range.

The growth rates of young vary with the temperature at the maternity roosts. It has been discovered that young in warmer roost situations grow more rapidly.

Breeding interval: These animals breed once per year.

Breeding season: Breeding occurs in the fall, when the bats enter their winter caves.

Range number of offspring: 1 to 1.

Average weaning age: 60 days.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); viviparous ; sperm-storing ; delayed fertilization

Average birth mass: 2.9 g.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)

Sex: male: 456 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 456 days.

As in all mammals, the mother provides milk to her growing young. Neonate gray bats are altricial. The mother attends to her young in a nursery cave. This is especially interesting, because the mother can locate her own offspring among the hundreds of baby bats which may be in the cave.

Parental Investment: altricial ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Mating occurs in September-October. Adult females store sperm through the winter and become pregnant soon after emergence from hibernation (Gutherie and Jeffers 1938). One young is born late in May or in early June (reported as mid-June for Oklahoma; flying as early as late June or early July). In Florida, young are weaned in mid-July (Layne 1978). Larger colonies are more successful in raising young. Most young are able to fly in 20-35 days, depending on colony size (may include up to 100,000+). First breeds in second year (Layne 1978).

Tuttle (1975) showed that growth rates of non-volant young are positively correlated with colony size, probably because increasing numbers of bats clustering together reduce the thermoregulatory cost per individual (Herreid 1963, 1967). In larger colonies, most young begin to fly from 20 to 25 days after birth, while in smaller colonies, or where colonies have been reduced due to disturbance, this time is increased to 30 to 35 days (Tuttle 1976). In severely reduced colonies, the young sometimes die before achieving flight (Tuttle in Brady et al. 1982). For newly volant young, growth rates and survival are inversely proportional to the distance from their roost to the nearest over-water foraging habitat (Tuttle 1976). Although mothers continue to nurse young for a period after the young are flying, juveniles are apparently left to learn how to hunt on their own (Tuttle and Stevenson).

M. grisescens is considered endangered by both the United States Fish and Wildlife service, according to the Endangered Species Act, and the IUCN Red List. Although CITES does not list this species of bat on Appendix I, II, or III, it is difficult to see why.

Gray bats began encountering problems in prehistorical times when tribes of Native Americans began camping and living in the entrances of caves. The smoke from their fires likely suffocated the bats. It is also thought that they were placed in stews by Native Americans.

Guano was extracted from nearly every substantial gray bat cave in the south during the Civil War. This guano was used for gunpowder, not for fertilizer, as is commonly thought. It is thought that gray bat colonies suffered some of their largest losses during the Civil War. Studies of guano deposits in formerly occupied caves shows that gray bats (a highly resilient species) were able to prosper once again in spite of these losses.

Currently, the biggest threat to gray bat populations appears to be human disturbance at hibernation and maternity colonies. The bats in the maternity colonies do not tolerate disturbance, especially when flightless newborn young are present. Thousands of baby bats may be dropped to their deaths or abandoned by panicked parents. A colony will even completely abandon a cave in the presence of excessive disturbance. This is particularly bad because so few caves are habitable for gray bats. Starvation in the winter can also be a problem. When bats are aroused during hibernation, their important fat reserves are used up more quickly. If the disturbance is intense or frequent enough the bats may starve to death.

Despite once being one of the most abundant mammals of the southeastern United States, M. grisescens has been listed as an endangered species since 1976. In 1970 the population was estimated at 2.25 million bats after a census of 120 caves. However, a census in 1976 of 22 of the 120 caves found that these colonies had declined by an average of 54 percent each.

Other factors that influence the decline of Gray Bat populations are: vandalism, cave commercialization, toxins (like organochlorine pesticides, PCB’s, and lead), natural causes like cave-ins and flooding (killing bats and destroying important habitat), loss of caves by inundation by man-made impoundments, and reduction of insect prey over streams that have been degragaded by excessive pollution and siltation. (Arkansas Game and Fish Commission, 199; Clawson and Clark, 1989)

Improper gating at cave entrances also presents a problem. Gates must allow the airflow, temperature, humidity, and amount of light entering the cave to be the same as it was prior to the gate installment. Although steel bar gates do provide excellent protection from humans, these gates may be detrimental to bats by giving predators a place to perch and wait for bats to emerge. It has also been found that bats prefer to use un-gated entrances. The alternative, if possible, would be to put up a chain link fence topped with barbedwire around the cave. This would prevent humans from entering the bats' caves, and allow the bats to fly OVER the gate, rather than through it. This would also protect them from predators perched on the gates.

Due to protective increases at high priority colony sites, declines in M. grisescens populations have been halted in some locations, and others exhibit an increase in population. Currently there are about 1.5 million gray bats in existence. Important conservation measures that have been taken to aid in the stabilization of the population, especially the acquisition of caves by the U.S. Fish and Wildlife Service. This organization is currently in control of Blowing Wind Cave in northern Alabama. This is the most important summer cave for gray bats known. Fern Cave is the largest hibernaculum for gray bats and is also under the protection of the U.S. Fish and Wildlife Service.

Additional conservation measures are needed to help M. grisescens. The purchase and protection through proper gating and restricted use of other gray bat caves is very important. Education of spelunkers and other cave visitors who may unintentionally disturb the bats is key, as well as the continuation of federal efforts to reduce pesticide use (or at least limit their lifetime in the environment).

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Myotis grisescens mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.

US Federal List: endangered

CITES: no special status

IUCN Red List of Threatened Species: near threatened

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Occurs mainly in the cave region of the eastern and central U.S.; highly vulnerable to disturbance; only a few caves contain most of the individuals; as a result of ongoing cave protection efforts, the total population is increasing.

Global Short Term Trend: Relatively stable (=10% change)

Comments: Cave protection efforts have led to recent population increases. By 1991, the rangewide population was stable and perhaps growing, apparently due to successful cave protection efforts (End. Sp. Tech. Bull. 16(6):9; Figg 1991). Since 1981, the maternity colony population in Oklahoma has increased from 56,000 to almost 150,000 (Grigsby et al. 1993, Hensley 2003).

The recovery plan criteria for change from endangered status to threatened status is documentation of permanent protection of 90% of Priority 1 hibernacula and documentation of stable or increasing populations at 75% of Priority 1 maternity caves during a period of five years; recent studies indicate that these criteria have been met (Harvey and Currie 2002).

Global Long Term Trend: Decline of 30-70%

Comments: Abundance declined by at least 50% from the 1960s to the early 1980s (Brady et al. 1982). The number of occupied caves has substantially decreased. In Missouri, 26 of 66 caves used historically by this species and surveyed in 1994 showed no evidence of recent use (see Figg and Bessken 1995). See Layne (1978) for information on decline in Florida.

Degree of Threat: AB

Comments: Cave disturbance has been the major factor in the decline. Cave protection efforts have greatly reduced this threat.

White-nose syndrome has been detected in this species, and this emerging disesase must be regarded as the major threat and one that could cause large, rapid declines.

The use of forestry insecticides and crop pesticides in areas adjacent to riparian corridors where gray bats forage may reduce the prey base or kill bats that ingest contaminated insects (Northern Prairie Wildlife Research Center). Some maternity and hibernating colonies are susceptible to human disturbance (Northern Prairie Wildlife Research Center).

Decline began with cave disturbance associated with saltpeter production during the Civil War. Some of the largest colonies were lost as a result of cave commercialization. Some caves were improperly gated.

The species is especially vulnerable due to its high fidelity to particular favored caves, and it is very sensitive to disturbance, including the mere presence of humans with lights; disturbance may result in bats moving to less favorable roosting places.

Other threats include pesticides, deforestation, and impoundment of waterways (and subsequent cave inundation).

Restoration Potential: The factors that make the gray bat vulnerable also make cave protection feasible. Since the majority of the population utilizes relatively few caves, protection of these sites should aid gray bat recovery (Resetarits, pers. comm., 1982). The ability to control factors such as water pollution, siltation, deforestation, and pesticide use will influence the ability of the gray bat to recover. As of 1992, the potential for recovery was very good. Some caves have had spectacular increases in gray bat populations due to proper gating and signs. In some instances, protecting caves that been abandoned has resulted in re-occupation (Currie, pers. comm., 1992).

Preserve Selection and Design Considerations: Winter roosts (hibernacula), summer maternity colonies, and bachelor caves should be protected. Migratory (temporary) roosts may also merit protection if they are permanent. Buffer zones of forest should be maintained and forested corridors to prime forage areas over river sand reservoirs protected. Steps should be taken to reduce pollution of waterways, siltation, or use of pesticides near caves (Resetarits, pers. comm., 1982).

Management Requirements: Major management concerns include reducing human disturbance at the cave site. Properly designed physical barriers are critical. Improperly constructed gates can alter the air flow, trap debris, and block the entrance by not allowing enough flight space (Brady et al. 1982). Temperature and humidity are directly related to the number of entrances to a cave. Most hibernating bats require exceptionally cold caves for hibernation and unusually warm caves for summer. Improperly constructed physical barriers can alter the exchange of air with the outside environment, which may cause significant changes in interior temperatures and humidity, causing the bats to abandon the cave (Currie, pers. comm., 1992). Improperly constructed gates may also subject the bats to severe predation as they attempt to pass through the gates (Tuttle 1977). Gray bats have accepted all properly designed gates but will not accept full gates (i.e., gates that completely fill the entrance). Wildlife managers should consult with members of the Gray Bat Recovery Team. Tuttle (1977) and Tuttle and Stevenson (1977) provided details on acceptable types of physical barriers. See also White and Seginak (1987) for information on gate design.

Public education and elimination of trails leading to cave entrances are important (Tuttle 1979, Brady et al. 1982). Signs may be appropriate at caves that are rarely visited or in conjunction with physical barriers. They should be located so that they are visible to people but do not impede flying bats or air flow. Brady et al. (1982) gave suggestions on the wording of signs. Signs may not be appropriate if they would attract people to an entrance that they otherwise would not have seen. Educating the public about the benefits of bats and communicating with local spelunkers and researchers should help reduce unintentional disturbance. Most people do not find caves if there is no trail leading to the entrance. Covering trails or preventing boat access will also reduce human disturbance.

Of importance are restoration of degraded foraging habitat and protection against environmental disturbance. Human disturbance at the cave site is a major cause of population decline (Barbour and Davis 1969, Tuttle 1979). Disturbance at maternity caves can result in thousands of flightless young being dislodged and falling to their deaths (Tuttle 1979). Caves used by nusery colonies should not be entered from late April through at least mid-July, particularly late May through early July (Brady et al. 1982); if a cave must be entered during this period, it should be restricted to a one-hour visit immediately following the evening emergence of adults (Layne 1978). Disturbance during the winter causes partial or complete arousal from hibernation. Brady et al. (1982) pointed out that a number of human disturbances during winter can exhaust the bats' limited energy reserves and result in a high mortality rate. Tuttle (in Brady et al. 1982) found that weight loss among gray bats during the first hour after arousal was 0.48 grams, compared to a normal hibernation loss of 0.01 grams per day.

Pesticides represent a major threat to the gray bat (Clark et al. 1978, 1980, 1982). At least one colony has been destroyed because of pesticide poisoning (Clark 1983). Dieldrin is a daughter product of aldrin and is sprayed in corn fields to control cutworms (larvae of Noctuidae moths; Clark et al. 1978). Bats consume moths with dieldrin and juvenile gray bats receive concentrated amounts through the female's milk. The rapid fat utilization in juveniles because of the stress of flight initiation can cause fatal concentrations in brain tissues (Clark et al. 1978). Dieldrin was banned in 1974, but provisions were made to use existing stocks. Clark et al. (1980) documented deaths in gray bats from heptachlor residues reflecting a change by local farmers from aldrin to heptachlor as stocks of aldrin have become depleted. Guano analyses can be used to identify major contaminants affecting bat populations.

Destruction of food, foraging habitats, and caves is also a management concern. Mayfly larvae are susceptible to aquatic pollution, turbidity, and siltation caused by strip mines in the watershed or farming practices (Fremling 1968, Tuttle 1979). Deforestation of the watershed reduces foraging habitat (LaVal et al. 1977, Tuttle and Stevenson in prep.). Young gray bats use the forest near the cave entrance for cover while perfecting flight abilities (Tuttle 1976). Both juveniles and adults use forested areas for protection from predators, specifically screech owls (Tuttle 1979). Impoundment of waterways has submerged important cave sites and made other caves more accessible to humans (Barbour and Davis 1969, LaVal et al. 1977, Tuttle 1979, Brady et al. 1982).

Natural calamities, such as submersion of the cave during a flood or a natural cave-in, also affect gray bat populations (Tuttle 1979). Flood frequency and magnitude can be affected by channelization and other human activities.

A revised and updated edition of The Indiana Bat and Gray Bat Comprehensive plan is in preparation and may be available by fall of 1992 (Clawson, pers. comm.).

Management Research Needs: Research the effects of habitat disturbance, water pollution, and siltation on food sources and the effects of pesticides and deforestation on population trends.

Global Protection: Several to many (4-40) occurrences appropriately protected and managed

Comments: The Tennessee Valley Authority sponsored a recovery project that resulted in the protection of two critical maternity sites: the Hambrick and Nickajack caves in Tennessee. Blowing Wind Cave in northern Alabama, the most important summer cave known for gray bats, has been acquired by the U.S. Fish and Wildlife Service and a gate has been placed across the entrance. Fern Cave, the largest known gray bat hibernaculum, has also been purchased by the Fish and Wildlife Service and is being managed for protection of the bats. The U.S. Fish and Wildlife Service also has acquired and protects additional caves in Alabama. To protect habitat, The Nature Conservancy has established six voluntary protection agreements with private landowners for gray bat maternity sites. The National Park Service restricts human access to six gray bat maternity caves on its lands and monitors them for possible disturbance. The Indiana Bat and Gray Bat Comprehensive Plan contains a detailed list of caves that have been protected or are currently being managed.

Needs: Occupied caves should be protected from human disturbance.

A buffer of undisturbed vegetation should be left around the entrances of caves inhabited by gray bats; wooded travel corridors between roosting and foraging sites should be protected; the use of herbicides and pesticides in areas adjacent to foraging and roost sites should be carefully controlled and monitored for unanticipated adverse effects (Alabama Forestry Commission).

They do not adversely affect humans. Gray Bats are great!

Insectivorous bats remove millions of insects a night, aiding in the control of these populations. Also, because of their roosting habits, inhabiting a small number of specific caves for long periods of time, these bats produce huge piles of feces on the floors of caves. Historically, this guano was used to make gunpowder during the civil war. Also, native americans used to eat these bats in stews.

Positive Impacts: food ; body parts are source of valuable material; produces fertilizer; controls pest population

Stewardship Overview: Stewardship needs include : (1) land protection agreements for important caves (consult U.S. Fish and Wildlife Recovery Plan), (2) gating, fencing, and/or posting of cave entrances (consult U.S. Fish and Wildlife and members of the Gray Bat Recovery Team), (3) protection and restoration of foraging habitat, and (4) monitoring of populations (consult U.S. Fish and Wildlife).

Comments: Monotypic (Decher and Choate 1995).