Eastern Small-Footed Myotis: Myotis Leibii

Image of a captured eastern small footed bat

Physical Characteristics Of The Eastern Small-Footed Myotis

The Eastern Small-footed myotis (Myotic leibii) bat is named after it’s small feet. The size of the average M. leibii measures as follows:

  • Total Length: 2-84 mm
  • Tail Length: 30-39mm
  • Hind Foot Length: 6-8mm
  • Forearm Length: 30-36mm
  • Wingspread: 212-248mm
  • Adult Weight: 3-8 g

The dorsal fur is pale yellowish-brown to a golden brown, with black ears and a black mask on the face. The bat’s ears are pointed and have a long tragus (prominence on the inner side of the external ear).

The belly hair varies from whitish to pale buff. The hair base is blackish on the back and very dark brown on the wing/tail membranes.

At the edge of the interfemoral membrane, the tail reaches (skin that stretches between the bat’s legs). This membrane’s base and the wing membranes’ undersurfaces are sparsely furred. 1Go To Source guides.nynhp.org -“Eastern Small-footed Myotis Myotis leibii”

Learn More: Small Sized Bats

Eastern Small-Footed Myotis Behavior

The nocturnal Eastern small-footed bats roost during the day and are active at night. They leave their roosting area around dusk during the summer, and they fly in and out of caves and through open fields.

They typically fly 0.3 to 6.0 meters above the ground. In-flight, they are easily distinguishable from other small bats by their unusually slow and fluttering motion.

They have a very powerful homing instinct, even if placed in a different location, returning to the same cave to hibernate. Within the same general area, eastern small-footed bats do not migrate but alter roosting sites. Unless weather forbids foraging, they move roosts daily. This frequent roosting location will have an abundance of insects, water, and foliage.

Males and females have different roosting selection criteria, and these preferences change during the reproductive season, such as women’s desire for more solar-exposed roosts.

Hibernation Habits Of The Eastern Small-Footed Bat

Picture of a roosting eastern small footed myotis bat

During the winter, eastern small-footed bats hibernate. Within their range, in mid-November, they are the last to hibernate and the first species to wake in March. Although they have been observed in groups hibernating, they hibernate alone more often.

Rather than vertically, they hibernate horizontally and hibernate on cave floors sometimes. Their small size makes it possible for them to squeeze into small cracks and crevices that provide predator protection. They prefer to hibernate at the mouths of caves and are often found in caves less than 150 meters long.

The body temperature drops to between 1 to 2 degrees Celsius during hibernaculum, higher during torpor (so that they can withstand temperatures below freezing). This drop-in body temperature decreases their metabolic rate by 95 percent relative to normal energy output.

At -9 degrees Celsius, they rise out of torpor. More often than co-hibernating species, they wake up from torpor, predisposing them to the rapid depletion of winter energy reserves. Despite the estimation that these arousals account for 84 percent of winter energy output, this increased awakening from torpor is synchronized to support immune function. The total body mass lost between December and April is around 16 percent. 2Go To Source animaldiversity.org -“Myotis leibii eastern small-footed myotis”

Eastern Small-Footed Myotis Reproduction Habits

In late summer to early fall, mating occurs with women being able to store sperm through hibernation. Between May and July, each female gives birth to a single pup. Eastern small-footed bats are believed to only give birth to one pup each season due to the newborn’s large size at birth.

Eastern small-footed bats form maternity colonies between 12 and 33 bats, and females take sole responsibility for caring for the offspring. 3Go To Source ncbwg.org -“Eastern Small-footed Bat”

Habitat Of The Easter Small-Footed Bat

For eastern small-footed bats, caves and mines are crucial winter habitats. This species is more tolerant of cold temperatures than other eastern bats and prefers hibernating on cave walls or ceilings under large rocks that make up cave floors.

Some researchers believe this species may be more common than it appears because of its secretive behavior. Popular summer roosting sites include caves, mines, hollow trees, under bark, cracks in rock walls, and ridge-top talus fields. This suggests that forested areas with caves, mines, rock outcrops, or talus provide essential summer habitats. 4Go To Source pgc.pa.gov -“Eastern Small-Footed Bat”

Eastern Small-Footed Myotis Range

The species is locally distributed throughout southern Canada and the eastern United States. Areas that Eastern small-footed bats have been seen include:

  • Southern Maine
  • Appalachian Mountains
  • Southern Illinois/Missouri
  • Southeastern Oklahoma
  • Central Tennessee
  • Central Arkansas 5Go To Source fw.ky.gov -“Eastern Small-Footed Myotis (Myotis leibii)”

Threats To The Eastern Small-Footed Bat Species

The eastern small-footed bat is considered a rare bat species within the United States, and it is’ facing a new threat. This disease is causing the eastern small-footed bat small population to plummet.

White-nose syndrome is a newly emerging fungal disease that attacks bats in caves and mines while they hibernate. The disease was discovered in 2006 in Albany, New York. Since then, nearly 7 million bats of six different species are estimated to have been killed by White-nose syndrome. 6Go To Source biologicaldiversity.org -“ASTERN SMALL-FOOTED BAT”

 

Sources:

  1. New York Natural Heritage Program. 2021. Online Conservation Guide for Myotis leibii. Available from: https://guides.nynhp.org/eastern-small-footed-myotis/. Accessed January 5, 2021.
  2. Scott, V. 2014. “Myotis leibii” (On-line), Animal Diversity Web. Accessed January 05, 2021 at https://animaldiversity.org/accounts/Myotis_leibii/
  3. NCBWG. “Eastern Small-Footed Bat (Myotis Leibii) | North Carolina Bat Working Group.” North Carolina Bat Working Group, www.ncbwg.org/eastern-small-footed-bat-myotis-leibii/. Accessed 5 Jan. 2021.
  4. PGC. “Eastern Small-Footed Bat.” Pennsylvania Game Commission, www.pgc.pa.gov/Wildlife/EndangeredandThreatened/Pages/EasternSmall-FootedBat.aspx. Accessed 5 Jan. 2021.
  5. “Kentucky Department of Fish & Wildlife Eastern Small-Footed Myotis.” Kentucky Department Of Fish And Wildlife Resources, fw.ky.gov/Wildlife/Pages/Eastern-Small-Footed-Myotis.aspx. Accessed 5 Jan. 2021.
  6. “Eastern Small-Footed Bat.” Center For Biological Diversity, www.biologicaldiversity.org/species/mammals/eastern_small-footed_bat/index.html. Accessed 5 Jan. 2021.