Eastern small-footed bats became a larger focus for research after fossils were discovered in the Cumberland Cave in Maryland in 1972 and Big Bone Cave in Tennessee in 1975. Species which are closely related were discovered in 1908 in caves in Arkansas from the middle to late Pleistocene. Myotis lebii was previously thought to be a subspecies of Myotis cililabrum, which inhabits areas of the western United States. Genetic analysis isolated M. leibii to its current range and determined that it was a separate species.
A 1979 study estimated that just 15 percent of all Myotis individuals in late-summer in Virginia caves are Myotis leibii. It is unclear if this is a true indication of their rarity or if they are often overlooked due to their concealed roosting sites within caves.
Eastern small-footed bats use echolocation to locate prey, typical among insectivores. Search-phase call is first used to locate an insect. While in pursuit, an approach-phase call is emitted. Immediately before consuming prey, they emit a terminal-phase call or feeding buzz. Both the approach-phase (pre-buzz call) and the terminal-phase (buzz call) are used to determine a range on the prey and maintain the location of the prey item. In one study the duration of search-phase calls were 2.8 ms and other studies have recorded calls as long as 5 ms. The minimum frequency is 46.1 KHz and the maximum frequency is 84.5 KHz.
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; echolocation ; chemical
In 2009, eastern small-footed bats were were placed on many conservation lists. In Alabama, Arkansas, Massachusetts, Maryland, Maine, New Hampshire, New Jersey, Oklahoma, Pennsylvania, West Virginia, Virginia, and Vermont they are listed as "critically imperiled". In Georgia, Kentucky, North Carolina, and New York, they is listed as "imperiled". In Connecticut, Massachusetts, Maryland, Missouri, North Carolina, New Jersey, New York, Ohio, Oklahoma, Tennessee, Virginia, West Virginia, and Georgia they are listed as a "species of special concern." In Pennsylvania and Vermont they are listed as "threatened," and are endangered statewide in New Hampshire. On a federal level, they are listed as a species of special concern and is under review by the Endangered Species Act. The state of Michigan gives no special status and the IUCN Red List lists them as least concern with a stable population trend. They are threatened by human activities because of their reliance on forests for foraging. Activties such as logging, wind turbines, agricultural and urban development contribute to foraging habitat destruction. Oil, gas, and mineral development can destroy roosting sites and contaminents can leak into local streams.
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%.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Bats are noted carriers of rabies, which results in a nearly 100% fatality rate if not detected on time. Five out of 45 species of bats has been recorded transmitting rabies to humans in the United States, one of which is suspected to be the eastern small-footed bat. Eastern small-footed bats might also carry Histoplasmosis, a disease caused by the fungus Histoplasma capsulatum. This presents itself with flu-like symptoms and disappears with antifungals and sometimes without need for any treatment. Eastern small-footed bats might also be considered a nuisance because they roost in human structures.
Negative Impacts: injures humans (carries human disease)
Eastern small footed bats prey on beetles and mosquitoes which are pests to humans and agriculture.
Positive Impacts: controls pest population
Eastern small footed bats host the following ectoparasites: mites (Androlaelaps casalis and Cryptonyssus desultorius), chiggers (Leptotrombidium myotis), and ticks (Ornithodorus kelleyi). Females in maternity colonies have an increased probability of exposure to ectoparasites. Females in northern regions of the United States are more likely to carry the Trypanosoma infection originating from the bat bug, Cimex brevis. These bat bugs are common in maternity colonies in Ontario.
Commensal/Parasitic Species:
Eastern small-footed bats are insectivores, specializing in nocturnal flying insects while staying 1 to 3 meters off the ground. Prey include beetles, mosquito, moths, and flies. Occasionally they feed on ants as well. One study of fecal samples during fall swarming found 7 orders, 1 superfamily, and 9 families of insects. The insects were very diverse but moths were consumed most abundantly. When foraging, they fly slowly and often feed over water where nocturnal insects are abundant and sometimes fill their stomach within an hour of the start of their foraging bout. They have also been observed feeding in dense forested areas using a gleaning strategy, which is described as eating insects from plants, rocks, or other surfaces. This type of feeding is considered the most efficient for bats with long-wing loading. Eastern small-footed bats have short, broad wings with rounded wingtips to that improve maneuverability in dense vegetation.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
Eastern small-footed bats are native to the United States and Canada. Despite their wide distribution, they are one of the rarest bats in North America. They range from as far north as Ontario, to as far south as Georgia, and as far west as Oklahoma. This species has been documented in the Ozark Mountains in Arkansas, Missouri and Oklahoma. They are found in the Appalachian mountains north to southeastern Canada and the New England states. In the southern parts of its range, eastern small-footed bats are limited to caves and rocky outcrops in Virginia, North Carolina, South Carolina, Tennessee, Kentucky, Alabama, and northern Georgia.
Biogeographic Regions: nearctic (Native )
Eastern small-footed bats roost during the spring and summer in buildings, bridges, caves, mines, in hollow trees, tunnels, rock crevices, beneath rocks, and in rocky outcrops. They prefer colder and drier hibernacula than other Myotis species, often seeking the coldest locations within a cave to roost and hibernate. They prefer short caves - often less than 150 m in length - and return to the same spot annually. Across combined observed accounts, 125 caves and mines throughout its range host eastern small-footed bats during hibernation. 90% of their habitat is on private land which is vulnerable to alteration. Only 3.8% of U.S. Forest service upland hardwood, bottomland hardwood, and pine-hardwood forests can support them. Required elevation differs by geographic location. In the 1997 Mammalian Species account by Best and Jennings, the elevation in Virginia is reported at 750 m but ranges from 300-750 m in Pennsylvania.
Range elevation: 300 to 750 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: caves
Eastern small-footed bats are estimated to live 6 to 12 years in the wild. This is affected by predation, habitat availability, and exposure to parasites or fungi. The maximum recorded lifespan in captivity was 12 years. In northern regions of their geographic range, males have a higher rate of survival (75%) than females (42%). This could be due to the higher demand on females during reproduction. Maternity colonies are not always present, so there is a large increase in energy output for thermoregulation of both pregnant and lactating females compared to those involved in clustering behaviors.
Eastern small-footed bats live about 6 to 12 years in the wild. This depends on predators, habitat availability, and parasites or fungi. In captivity, the maximum recorded lifespan is 12 years. In northern parts of their range, males are more likely to survive than females. The survival rate for males is 75% and the survival rate for females is 42%. This might be because females have to use more energy during the reproduction process. Females who are pregnant or nursing also use more energy to stay warm if they aren't in a maternity colony.
Range lifespan
Status: captivity: 12 (high) years.
Typical lifespan
Status: wild: 6 to 12 years.
Average lifespan
Status: captivity: 12 years.
Eastern small-footed bats are the smallest of the Myotis genus ranging from 3.5 to 6 grams with a length of 75 to 85 mm and a wing span of 210 to 250 mm. They derive their common name from the fact that they are the only member of the Myotis genus (in Virginia) with feet measuring less than 9 mm. The sexes are similar in coloration and size. Their fur is black at the root with brown shiny tips; this gives them their glossy yellowish-brown appearance. Their underside is a dull grayish-brown. The completely black face mask is its most unique feature. They also have black ears, wings, and interfemoral membranes (a stretch of membrane that extends between the legs to the tail). Females have two mammae (or milk glands). They have a strongly keeled calcar (a protruding piece of cartilage on the hind leg to support the intefemoral membrance) and a pointed tragus (a fleshy projection which extends from the base of the ear) of about 9 mm in length. Their skulls are relatively flat, short, and fragile. Their dental formula is: incisors 2/3, canines 1/1, premolars 3/3, and molars 3/3. Their foreheads slope gradually away from the rostrum lacking the typical prominent forehead of most Myotis species. Their ears are erect and broad at the base and their noses are blunt. Their tails extend beyond the interfemoral membrane.
Eastern small-footed bats are often confused with two other members of the bat family: little brown myotis (Myotis lucifugus) and tri-colored bats (Perimyotis subflavus). Little brown myotis are larger in size and have no mask or keel on the calcar. Tri-colored bats have a blunt tragus, no keel, and a pink coloring on their forearm.
Range mass: 3.5 to 6 g.
Range length: 75 to 85 mm.
Range wingspan: 210 to 250 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
During the summer months, eastern small footed bats are found in cracks and crevices which reduce the chance of predation. Little is known about their specific predators, but bats are often eaten by hawks and owls, snakes, raccoons, and weasels.
Swarming, which is important for mate selection, breeding, and hibernacula selection, occurs from late summer through early fall. Eastern small-footed bats are polygynandrous, so both males and females have many mates.
In the late summer through early fall, many eastern small-footed bats gather together in the same spot. This is important for breeding and for choosing locations to hibernate. Both males and females have multiple mates.
Mating System: polygynandrous (promiscuous)
Maternity colonies have been observed in New Hampshire, Kentucky, North Carolina, South Carolina, and Ontario. These colonies ranged from a 12 to 33 individuals and the roost locations were diverse. Thirteen individuals were found in rock crevices, 20 in guardrail crevices on a concrete bridge, 12 behind a shed door, and others in wood piles and picnic shelters. Little is known about their breeding behavior. However, one study found a maternity colony in an abandoned cabin in North Carolina. This colony consisted of 33 individuals: 22 adult females, 1 non-reproductive adult male, 3 juvenile males, and 7 juvenile females. Female eastern small-footed bats typically have one offspring per year between May and July. Sperm is stored throughout hibernation, where the female is in sub-estrus, from mid-November to March. Mating has also been documented during the winter if a male and a female are aroused from hibernation at the same time. This is when the female releases an egg and delayed fertilization occurs.
During reproduction, males initiate copulation and the female's role is passive. Both sexes are quiet throughout copulation. The male mounts the female and tilts her head back to a 90 degree angle by biting down on the hairs at the base of the skull. The male uses his thumbs to further stabilize his position on the female as he moves his projecting penis below her interfemoral membrane. The interfemoral membrane does not hinder posterior copulation due to the free movement of the penis. After the male has entered the female the penis appears to move rapidly and independently of any movements by the hindquarters.
Newborn eastern small-footed bats weigh 20 to 35% of their mother's weight. This large size is thought to limit the number of offspring to one because another fetus would overexert the mother while foraging. There is a 1:1 sex ratio at birth. When raising young, females choose the site with the highest solar exposure to decrease energy expenditure. Warmer sites provide thermal stability for young when the female goes out on foraging trips.
Breeding interval: Once per year
Breeding season: Fall swarm
Range number of offspring: 1 to 1.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; sperm-storing ; delayed fertilization
Average number of offspring: 1.
Only females care for newborns. They go on foraging trips for food, feed, protect, and teach the young. Mothers leave the newborn soon after birth to look for food. Weaning time is not known.
Parental Investment: female parental care ; pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
The eastern small-footed bat (Myotis leibii) is a species of vesper bat. It can be found in southern Ontario and Quebec in Canada and in mountainous portions of the eastern United States from New England to northern Georgia, and westward to northern Arkansas.[1] It is among the smallest bats in eastern North America[2] and is known for its small feet and black face-mask. Until recently, all North American small-footed Myotis were considered to be "Myotis leibii". The western population is now considered to be a separate species, Myotis ciliolabrum. The Eastern small-footed bat is rare throughout its range, although the species may be locally abundant where suitable habitat exists.[3] Studies suggest white-nose syndrome has caused declines in their populations.[4][5][6] However, most occurrences of this species have only been counted within the past decade or two and are not revisited regularly, making their population status difficult to assess. Additionally, most bat populations in the Eastern U.S. have been monitored using surveys conducted in caves and mines in the winter, but Eastern small-footed bats hibernate in places that make them unlikely to be encountered during these surveys.[3][7] Perhaps as a result, the numbers of Eastern small-footed bats counted in winter tend to be low and they are relatively variable compared to other species of bats. Many biologists believe the species is stable, having declined little in recent times, but that it is vulnerable due to its relatively restricted geographic range and habitat needs.
The eastern small footed bat is between 65 and 95 millimeters in length, has a wingspan of 210 to 250 millimeters, and weighs between 4 and 8 grams (with 4.0-5.25 grams being typical).[8] The bat got its name from its abnormally small hind feet, which are only 7 to 8 millimeters long.[7] A defining characteristic of this bat is its appearance of having a dark facial "mask", created by nearly black ears and muzzle.[7] In most individuals, the ears, wings and interfemoral membrane, (the membrane between the legs and tail) are dark and contrast starkly with the lighter colored fur on the rest of the body.[9] The fur on the dorsal side of their body is dark at the roots, and fades to a light brown at the tips, which gives the bats a signature shiny, chestnut-brown appearance. Like all bats, the eastern small-footed bat has a patagium that connects the body to the forelimbs and tail, aiding in flight. Their head is relatively flat and short, with a forehead that slopes gradually away from the rostrum, a feature that is unique to other individuals in the Myotis species.[7] They have erect ears, which are broad at the base and a short flat nose. Like other Myotis, they have a pointed tragus. They also have a distinctly keeled calcar (cartilagenous rod on the hind legs to support the interfemoral membrane). Their forearm length, which is less than 34 mm, can be used to distinguish them from all other Myotis in Eastern North America. Tail is between 25-45 millimeters in length and protrudes past their interfemoral membrane, and they have a dental formula of 2/3, 1/1, 3/3, 3/3.[7] Eastern small-footed bats are most likely to be confused with the little brown bat (Myotis lucifugus), especially in individuals where the face-mask is less apparent; however, forearm size less than 34mm and presence of a keeled calcar are considered diagnostic.
The range of this species includes Northern Arkansas and southern Missouri, East to the Appalachian Mountains and Ohio River Basin, South into northern Georgia, and North into New England, southern Ontario and Quebec.[10] Distribution is spotty within their entire range, and they are considered to be uncommon. These bats are mostly associated with rock formations in deciduous or coniferous forests. Most observations have been from mountainous areas from 240–1125 meters in elevation, where exposed rock formations are more common. However, the species has also been observed at lower elevation rocky sites.[11] During the spring, summer, and autumn they predominantly roost at emergent rock-outcrops such as cliffs, bluffs, shale barrens, and talus slopes, but also man-made structures, including buildings, joints between segments of cement guard rails, turnpike tunnels, road-cuts, and rip-rap covered dams. The largest populations of Myotis leibii have been found in New York, Pennsylvania, West Virginia and Virginia. (red list) The total count of individuals across all known hibernacula is only 3,000, with roughly 60% of the total number from just two sites in New York.[12] Unfortunately, 90% of their habitat is on private land, which makes it difficult to protect them.[12]
Eastern small-footed bats are believed to feed primarily on flying insects such as beetles, moths, and flies[13][14][15] and are capable of filling their stomachs within an hour of eating.[16] They are nighttime foragers and usually forage in and along wooded areas at and below canopy height, over streams and ponds, and along cliffs. Moths compose nearly half of their diet, and they forage primarily on soft-bodied prey.[17][14] It is believed that the avoidance of hard prey is due to their small, delicate skulls. The food habits of eastern small-footed bats are similar to those of the closely related California Myotis (M. californicus) and western small-footed bat (M. ciliolabrum), as well as other North American Myotis (e.g., little brown bat, (M. lucifugus), and northern bat, (M. septentrionalis).[18][15]
The eastern small-footed bat is most often detected during hibernation, and has been counted at approximately 125 caves and mines.[19] They are one of the last species to enter hibernation in the fall and the first to leave in the spring, with a hibernation period lasting from late November to early April. They have been found in relatively cold caves and mines and can tolerate lower temperatures than other bat species (Whitaker and Hamilton 1998). Unlike most other bat species, they often hibernate in caves and mines that are relatively short (150m) and they are most often found hibernating near the entrance where temperatures sometimes dip below zero and the humidity is low (Barbour and Davis 1969; Merritt 1987; Harvey 1992). Such locations may put them at a greater risk of white nose syndrome, although the species appears to have been less impacted by the disease than some others. Estimates from winter cave and mine surveys suggest the disease caused a 12% decrease in their overall population between 2006 and 2011, which is lower mortality than other species of Myotis experienced at the same sites.[20] Other aspects of their biology make them difficult to count, but also probably offer some protection from WNS. For example, they tend to hibernate individually or in groups of less than 50, and often in small crevices.[16] Bat biologists have speculated that the species also may hibernate outside of caves and mines. Observations of eastern small-footed bats in western Virginia roosting in crevices along sandstone cliff faces in winter support this idea.[21]
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There is little published information about the spring and summer roosting locations of eastern small-footed bats. The first study into the summer roosting habits was only done in 2011 so information is scarce. This study discovered that these bats most commonly use ground level rock roosts in talus slopes, rock fields and vertical cliff faces for their summer roosts.[22] On average they change their roosts every 1.1 days, males travel about 41 meters between consecutive roosts and females around 67 meters. They also found that females roosting sites were closer to ephemeral water sources than male's roosts. Females who have young require roost sites that receive a lot of sunlight in order to keep the pups warm while the mother is away from the roost.[23] Summer roosting habitats were previously considered difficult to find, but several recent studies have shown that the species is relatively easy to locate if survey efforts are focused near appropriate rocky habitats.[3][11][24]
As with many other species of bats, the eastern small-footed bat usually has only one offspring a year, although a few instances of twins have been noted. This k-selected reproductive strategy means that their populations are not capable of withstanding high mortality rates, making them particularly vulnerable to sudden population declines. Mating most often occurs in autumn and the female stores the male's sperm throughout hibernation in the winter. Fertilization occurs in the spring once the females are active again, and gestation occurs between 50–60 days with young being born in late May and early June.[3] Mating has also been noted to occur throughout the hibernation period, if individuals are awake. During the time of breeding, large number of bats come together in a behavior commonly known as "swarming." All bats of this genus are polyandrous, meaning they mate with multiple partners throughout the mating period. This mating behavior allows them to increase the likelihood of copulation, and therefore increase their reproductive success.
Male bats initiate copulation by mounting the female and tilting her hear back 90 degrees. The male then secures his position by biting and pulling back on the hairs at the base of the female's skull. The male then uses his thumbs to further stabilize his position and enters the female under her interfemoral membrane. Both individuals have been noted to be very quiet during copulation. Once the process is over the male dismounts the female and flies away to find another mate.
Newborn bats (called "pups") weight 20–35% of their mother's body weight and are completely dependent on their mother.[10] The young's large body size is believed to lead to high-energy expenditure from the mother, which is what limits her to only having one offspring a year.[23] Adult males and females may use the same rock outcrops, but as is typical for other bats in the genus, the sexes typically roost separately from one another. In Virginia, both sexes appear to roost alone or occasionally in pairs, except females begin to congregate into maternity groups around the time pups are born and likely maintain these "maternity colonies" until pups are weaned.[3][24] Size of maternity colonies is not well studied, but they appear to form smaller groups than other bats in the genus.
The main threat to this species is habitat disturbance, both natural and human caused. They also likely are under threat from white-nose syndrome, pollution (especially water pollution) and human disturbance during hibernation. Very low levels of light, noise and heat are sufficient to wake hibernating bats. Once awake bats begin to expend energy and deplete critical fat reserves needed to survive winter. If disturbances within hibernacula are repeated, bats (especially juveniles) are likely to die. This phenomenon was well documented in other species of bats in eastern North America, such as the Indiana bat (Myotis sodalis) and gray bat (Myotis grisescens).
White-nose syndrome is a fungal infection that attacks bats while they hibernate. In the first 6 years following the discovery of WNS, 7 million bats of 6 different species were estimated to have been killed by the disease. Early estimates of impacts from white-nose syndrome based on bats counted in hibernacula suggested a 12 percent decline in eastern small-footed bat populations.[6] However, changes in capture rates during summer, in West Virginia and New Hampshire, suggested declines from WNS may have been more severe (68-84%) in some regions.[4][5] Due to their dependency on exposed and predominantly non-forested rock outcrops for roosting sites, they may be at risk from "natural" processes such as forest encroachment and establishment of more mesic forest types due to suppression of forest fires. Likewise, the species is likely threatened a host of human activities that impact rocky habitats or the surrounding areas where eastern small-footed bats forage, such as: mining, quarrying, oil and gas drilling and other forms of mineral extraction, logging, highway construction, wind energy and other forms of agricultural, industrial and residential development. However, it is also likely that some of the above activities have created roosting sites by providing exposed rock faces.
The eastern small-footed bat is listed as endangered by the IUCN. Many states in the US in which the bat resides have begun listing it as threatened, and have begun conservation efforts in order to improve its numbers. In Canada, eastern small-footed bats are considered endangered in Ontario, and "threatened or vulnerable" in Quebec. The species is not protected under the US Endangered Species Act, but was a former C2 candidate for listing prior to the abolishment of that category by the U.S. Fish and Wildlife service in 1996.[25] Some states (e.g. Pennsylvania) have given the species legal protection while others have recognized its apparently low numbers and consider the eastern small-footed bat a species of concern. In the report Species of Special Concern in Pennsylvania,[25] the Pennsylvania Biological Survey assigned Myotis leibii the status of "threatened". Other states, such as Virginia, are currently working to get the eastern small-footed Myotis legal protection. Despite these efforts not many conservation projects have been initiated to help the species. Due to their strange hibernation patterns, and the lack of information regarding their spring and summer roosting sites, meaningful conservation efforts are very difficult. The species will not usually use bat boxes like many other bat species, so construction of bat boxes is not an appropriate action to mitigate against habitat disturbance issues. However, the species is known to roost in man-made rocky habitats such as road cuts and rip-rap embankments, suggesting it should be possible to create roost sites for conservation purposes.
The eastern small-footed bat has been recorded living up to the age of 12 years.[8]
The eastern small-footed bat (Myotis leibii) is a species of vesper bat. It can be found in southern Ontario and Quebec in Canada and in mountainous portions of the eastern United States from New England to northern Georgia, and westward to northern Arkansas. It is among the smallest bats in eastern North America and is known for its small feet and black face-mask. Until recently, all North American small-footed Myotis were considered to be "Myotis leibii". The western population is now considered to be a separate species, Myotis ciliolabrum. The Eastern small-footed bat is rare throughout its range, although the species may be locally abundant where suitable habitat exists. Studies suggest white-nose syndrome has caused declines in their populations. However, most occurrences of this species have only been counted within the past decade or two and are not revisited regularly, making their population status difficult to assess. Additionally, most bat populations in the Eastern U.S. have been monitored using surveys conducted in caves and mines in the winter, but Eastern small-footed bats hibernate in places that make them unlikely to be encountered during these surveys. Perhaps as a result, the numbers of Eastern small-footed bats counted in winter tend to be low and they are relatively variable compared to other species of bats. Many biologists believe the species is stable, having declined little in recent times, but that it is vulnerable due to its relatively restricted geographic range and habitat needs.
