Corynorhinus rafinesquiiRafinesque's big-eared bat

Geographic Range

Rafinesque's big-eared bats Corynorhinus rafinesquii are endemic to North America and are found throughout most of the south-central and southeastern United States. Their range extends no further north than 40.9 degrees north in Illinois, Indiana, and Ohio. In the east, its range extends to 37.0 degrees north is found no further north than southern Virginia. The range extends eastward to the Atlantic coast and westward to southeastern Texas just east of Dallas, at about 96.6 degrees west. There are two subspecies of the Rafinesque's big-eared bat, Corynorhinus rafinesquii rafinesquii and Corynorhinus rafinesquii macrotis. Corynorhinus rafinesquii rafinesquii is mainly found in the northern and western reaches of the range, whereas Corynorhinus rafinesquii macrotis is found in the southeastern states. (Arroyo-Cabrales and Alvarez-Castañeda, 2008; Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; O'Shea, et al., 2003)

Habitat

The habitat requirements of Corynorhinus rafinesquii are dependent on the availability of foraging habitat and roost habitat. Foraging habitat includes mature bottomland hardwoods, young pine Pinus stands, oak-hickory (Quercus-Carya) forests, open field edges, and riparian habitats such as swamps and stream edges. Foraging habitats must contain a high diversity of woody plants in order to satisfy the needs of their lepidopteran prey. The subspecies Corynorhinus rafinesquii rafinesquii is found in the northern region of the range and commonly forages in mature hardwood habitats along ridgelines and corridors. The subspecies Corynorhinus rafinesquii macrotis inhabits more Coastal Plain foraging habitats, focusing on upland pine stands. This subspecies will also selectively forage in mature oak and hickory forests. For unknown reasons, yellow polar (Liriodendron tulipifera), American beech (Fagus grandifolia), and maple (Acer) stands are avoided by both subspecies when foraging. The roost habitat of the Rafinesque’s big-eared bat can be further broken into three categories: hibernating roosts, day roosts, and maternity roosts. Roost habitats mainly consist of caves, dead or decaying trees, and human structures such as barns, houses, culverts, mine shafts, and bridges. All types of roosts are dependent upon temperature stability. Most human structures occupied by Rafinesque’s big-eared bats are abandoned due to a high sensitivity to human disturbance. A roost temperature of 10 to 15 degrees Celsius is required year-round. Maternity roosts are used from late April to mid-July and are used for rearing pups. Reproductively active females and their young only occupy these roosts. Maternity roosts can consist of caves, snags, or human structures. Day roosts of female Rafinesque’s big-eared bats are used throughout early spring and early fall (March-April and August-October). For males, day roosts are used consistently throughout March-October. Day roosts are normally comprised of snags, under tree bark, in barns, under bridges, in mine shafts, in culverts, and occasionally in caves. Hibernating roosts, or hibernacula, are used throughout the cold winter months (approximately November to February). Ideal hibernacula for Rafinesque’s big-eared bat are caves or mine shafts that maintain a constant temperature of about 11 degrees Celsius. In the southern portion of the range, hibernacula have included human structures as well as snags. Roost choice is dependent upon proximity to a water source as well as foraging habitat. Rafinesque’s big-eared bats are not known to travel much further than 2.5 km from the roost site. Studies have shown that they demonstrate roost fidelity from year-to-year for all types of roost habitat. (Arroyo-Cabrales and Alvarez-Castañeda, 2008; Carver and Ashley, 2008; Hurst and Lacki, 1997; Hurst and Lacki, 1999; Johnson and Lacki, 2013; Lacki and Bayless, 2013; Menzel, et al., 2001; O'Shea, et al., 2003; Trousdale and Beckett, 2004)

Physical Description

Corynorhinus rafinesquii has relatively flat, dull fur and is brownish-gray in color, sometimes with a reddish hue on the dorsal side. The ventral fur is much lighter, with fur that is dark at the base and light at the tip. This bat is about 10.5 cm in total snout-vent length. The toe hairs extend noticeably beyond the toe. This bat is known for its large ears, which are about 3 cm long in adults. A long, pointed tragus is present in the inner ear that is roughly two-thirds the total ear length. Rafinesque’s big-eared bats have the ability to curl their ears back, which make the ear resemble ram's horns.

There is no difference in appearance between the two subspecies of Rafinesque’s big-eared bat. An additional cusp is present on the upper incisor of Rafinesque's big-eared bat that is not seen in other species in the genus Corynorhinus. The dental formula is: 4/6 2/2 4/6 6/6.

Adults can weigh from 7 to 13 grams and demonstrate sexual dimorphism. Females are normally about one gram larger than adult males. Newborn pups are born naked, without fur and weigh between two to three grams. Neonates will resemble adults in appearance within three weeks of birth.

Large, protruding pararhinal glands are present on the upper side of the snout with extended nostril openings. Rafinesque’s big-eared bats have a wingspan of approximately 25 to 30 cm. Forearm length is between 38 and 45 mm in adults.

Rafinesque’s big-eared bats closely resemble Townsend’s big-eared bats (Corynorhinus townsendii) but are distinguishable by several key characteristics. The main difference between the two is the presence of the additional cusp on the upper incisor of the Rafinesque’s big-eared bat. There is also a slight difference in fur color between the two species. Townsend’s big-eared bats tend to have relatively lighter dorsal coat and less variation in ventral fur color than Rafinesque’s big-eared bats. (Arroyo-Cabrales and Alvarez-Castañeda, 2008; Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; Menzel, et al., 2002; O'Shea, et al., 2003)

  • Sexual Dimorphism
  • female larger
  • Range mass
    7 to 13 g
    0.25 to 0.46 oz
  • Average mass
    8.1 g
    0.29 oz
  • Average length
    10.5 cm
    4.13 in
  • Range wingspan
    25 to 30 cm
    9.84 to 11.81 in

Reproduction

Corynorhinus rafinesquii mates from late October to late November, before hibernating. Mating occurs during fall swarms in which males and females gather outside of cave entrances and commence mating. Female Rafinesque's big-eared bats are polygynandrous and delay fertilization until after hibernation. Exact length of gestation is unknown. Not much has been published on the mating systems of Corynorhinus rafinesquii. Only hypotheses about the systems have been reported in the literature. For example, Clark (1990; cited in Lacki and Bayless 2013) suggested that this species has a polygynous mating system. During the months of fall swarm, she hypothesized that males defend a territory and encourage multiple non-territorial females to mate with them. Rafinesque’s big-eared bats are believed to become reproductively active after one year, but little data are available on reproductive development. The reproductive status of male Rafinesque’s big-eared bats is distinguishable by the presence of swollen testicles. (Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; Lacki, et al., 2007)

Rafinesque’s big-eared bats use internal fertilization. Females form maternity colonies during late May and early June. During this time females give birth to a single naked pup, usually weighing 2.3 to 2.6 grams. Females give birth to neonates while roosted in an upright position, dropping the newborn pups into the membrane between their hind limbs known as the uropatagium. These bats are thought to be able to distinguish their young by chemoreception of unique odors produced by newborn pups. Offspring generally have darker pelage within the first three weeks of life that molts into adult pelage within eight weeks in southern parts of their range, and 10 to 12 weeks in the northern parts of their range. Within 4 to 5 weeks after birth, these bats resemble adults in size. On average, Rafinesque’s big-eared bats become sexually active around one year of age. (Johnson and Lacki, 2013; Jones, 1977; Lacki and Bayless, 2013; Lacki, et al., 2007)

  • Breeding interval
    Rafinesque's big-eared bats will mate multiple times during the late summer and early fall.
  • Breeding season
    The breeding season is from September through October.
  • Average number of offspring
    1
  • Range weaning age
    3 to 4 weeks
  • Range time to independence
    5 to 6 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Rafinesque’s big-eared bat young are altricial. These pups are dependent upon maternal care for three to four weeks during which time they rely on nutrition from their mother’s milk. Upon the loss of milk teeth, around four weeks of age, these bats gain permanent dentition and forgo suckling. Young Rafinesque’s big-eared bats begin practicing flight within three weeks of birth and become competent in flight around five weeks. Oftentimes, bat captures in late July and early August occur in pairs of mothers and juveniles. Such observations have led to speculation that there may be a teaching period in which mothers forage with their young in order to demonstrate proper foraging techniques. (Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; Lacki, et al., 2007)

  • Parental Investment
  • altricial
  • female parental care
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Corynorhinus rafinesquii has a lifespan that depends on several factors, including social behaviors, roost selection, and geographic location. The longest recorded lifespan was of a female captured in West Virginia that was ten years and one month old (Paradiso and Greenhall, 1967). Little data are available on the lifespan of this bat in the wild. Most bats can only be tracked via band recoveries, and Lacki (2013) acknowledges that most banded individuals aren’t recaptured after three years. There are speculations that banded individuals may avoid recapture by relocating, or becoming savvy to avoid nets. There are no scientific sources reported on captivity of this bat, although similar species (e.g., Corynorhinus townsendii virginianus, Virginia big-eared bats) perish at an accelerated rate in captivity. In 2010 the National Zoo took forty Virginia big-eared into captivity for ensured preservation of the subspecies, within four months only eleven bats remained. The zoo found that the most substantial challenge with keeping these bats in captivity was to stimulate feeding behaviors within a confined area. (Cockrum, 1956; Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; O'Shea, et al., 2003)

  • Range lifespan
    Status: wild
    10 (high) years

Behavior

Seasonal behaviors of Corynorhinus rafinesquii can be broken into three categories, fall swarming and mating, maternity colony formations and pup rearing, and hibernation. Mixed sex roosts are occupied throughout the early spring (March through April), and fall-winter months (August through February). Both sexes occupy day roosts as well as hibernacula together. Rafinesque’s big-eared bats cluster together when roosting and can vary in number of individuals from 2 to 100, while some remain solitary. It is hypothesized that cluster size is inversely related to roost temperature. While roosting, Rafinesque’s big-eared bats hang upside down with the ventral side resting along a substrate. These bats demonstrate grooming behaviors while roosting, which is believed to strengthen social bonds amongst conspecifics. There is no preference in roost choice between sexes. During the summer months (May to August), reproductively-active females gather in maternity colonies and care for their offspring. Roost fidelity is often seen in maternity roosts and these will be used for multiple seasons, upwards of 5 to 10 years, depending on structural integrity of the roost. Maternity roosts can consist of several roost locations including roosts in dead trees, under bridges, and in abandoned human structures. Maternity roost structure is generally comprised of a main home roost with several other satellite roosts, depending on habitat quality and roost availability. Females fly with the young clinging to their ventral side in order to relocate to different roosts. This behavior does not occur during foraging. Males and non-reproductive females continue to use day roosts throughout the summer months. During the fall months (September to October), Rafinesque’s big-eared bats gather in fall swarms and begin to mate. These swarms usually occur outside of cave entrances where mixed sex roosts are located. Rafinesque’s big-eared bats usually do not share roosts with other bat species. However, in the northern parts of the range these bats may occasionally roost with tri-colored bats (Perimyotis subflavus) and Virginia big-eared bats (Corynorhinus townsendii virginianus). Rafinesque’s big-eared bats hibernate for as long as three to four months in the winter (November to February) to endure cold temperatures. Length of hibernation can vary depending on location and severity of weather from year to year. In the northern portions of their range, Rafinesque’s big-eared bats may undergo a state of torpor during summer months. These bats have the ability to initiate immediate flight from a stationary position if aroused. Although while hibernating it may take several minutes for bats to initiate flight if aroused.

Rafinesque’s big-eared bats usually leave the roost well after dark and return in the early morning before twilight hours. They are versatile flyers and are able to travel through cluttered corridors as well as hover in order to capture stationary prey. (Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; Lacki, et al., 2007; Menzel, et al., 2001)

  • Range territory size
    0.616 to 2.253 km^2
  • Average territory size
    1.606 km^2

Home Range

Home range varies depending on location and habitat quality although Menzel et al. (2001) reported the average home range of 5 male Rafinesque’s big-eared bats in South Carolina was 93.1 ha (range 61.6 to 225.3 ha). Little literature is available for the size of the home range in females; it is speculated that it is smaller than males and more variable with the season. There are little data available on territory maintenance of these bats and there is likely overlap between individual territories. (Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013; Lacki, et al., 2007; Menzel, et al., 2001)

Communication and Perception

Rafinesque's big-eared bats use a low frequency call during echolocation, compared to many bat species in the genus Myotis. All calls are less than ten milliseconds in length and can be described as a frequency-modulated sweep. The range of the call during the sweep usually begins at about 40 kHz and ends around 20 kHz. The nature of the low frequency call makes it difficult to record on acoustic detectors and is believed to aid in the location of stationary prey. While in flight, this bat continuously has its mouth open in order to produce echolocation calls. Contrary to popular belief, this bat also uses its eyesight while in flight in order to avoid obstructions. The elongated nostrils of Rafinesque's big-eared bats are said to aid the production of ultrasonic sounds, which is thought to help individuals maintain spatial distribution during foraging. Their large ears also aid in what is known as passive listening in order to locate stationary prey. Rafinesque's big-eared bats also have the ability to produce social calls. Although not much information is available on the diversity of social calls for this species, it is thought that several types of social calls are used, including alarm calls, mating calls, and territorial calls. Chemical signals and tactile communication are also suspected to aid in offspring recognition and roost location. There is no known difference in communication and perception between subspecies. (Lacki and Bayless, 2013; Loeb and Britzke, 2010)

Food Habits

Rafinesque's big-eared bats are versatile flyers and are able to capture prey by gleaning as well as aerial hawking. The ability to hover and passively listen allows them to be especially successful in the capture of stationary prey species. Rafinesque's big-eared bats forage about one meter off the ground in locations with plenty of vertical and horizontal surface that is necessary for gleaning. The average area of foraging habitat for Rafinesque's big-eared bats is 137.4 hectares and may be occupied by several individuals. Conspecifics are able to maintain a constant spatial distribution during foraging by picking up one another’s echolocation calls and avoiding overlap. Rafinesque's big-eared bats use feeding perches, where they consume prey that they have caught. A late flyer, they usually leave the roost to forage several hours after dark. Males may demonstrate biphasic foraging patterns using two different foraging trips a night. The first being from about an hour after dark until midnight and the second beginning around four in the morning until just before sunrise.

The areas used for foraging can differ in individuals based on time of year, sex, and reproductive condition. Rafinesque’s big-eared bats are forest habitat generalists and target areas along forest edges, along cliff walls, and in riparian corridors.

Rafinesque's big-eared bats are Lepidopteran specialists. Studies have shown that more than 80% of the diet consists of various lepidopteran species including six families of moths and 22 species. Wingspan of lepidopteran prey is a limiting factor. The average wingspan of lepidopteran prey is between 47 and 70 millimeters. The family Noctuidae makes up the bulk of the diet at about 39 percent. The five other main families include Arctuidae, Geometridae, Megalopygidae, Notodontidae, and S<phingidae>. Studies have shown that Rafinesque's big-eared bats also forage on beetles (Coleoptera), cicadas (Hemiptera), flies (Diptera), true bugs (Hemiptera), bees and ants (Hymenoptera), and caddis flies (Trichoptera). There is no evidence of difference in food habits between subspecies. (Gregory, et al., 2014; Hurst and Lacki, 1997; Johnson and Lacki, 2013; Lacki and Bayless, 2013; Lacki and Ladeur, 2001)

  • Animal Foods
  • insects

Predation

Due to the nocturnal nature and versatile flying abilities of Rafinesque’s big-eared bats, there are few known predators that are successful at capturing these bats while in flight, most predation occurs while bats are roosted. Bats that choose less cryptic roost locations such as abandoned buildings tend to be more susceptible to predation. There are few reported cases of observed predation of these bats however black rat snakes (Pantherophis alleghaniensis), raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), and house cats (Felis catus) are known predators of this species. In some cases young Rafinesque’s big-eared bats may become dislodged from their roosts and fall to the ground leaving them vulnerable to predators, including snakes and terrestrial predators. (Harvey, et al., 2011; Jones, 1977; Lacki and Bayless, 2013)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

This bat is a lepidopteran specialist and significantly controls insect populations throughout its range. Rafinesque’s big-eared bats host both ectoparasites and endoparasites. A study by McAllister et al. (2005) reported a variety of gastrointestinal helminths present in 10% of the observed bats in Arkansas. The three main parasites recorded in this study include one parasite in the class Cestoda (Vampirolepis) and two parasites from the phylum Nematoda (Physaloptera and Capillaria palmata). These specific parasites are common to occur in the stomach, small intestine, and feces of the Rafinesque’s big-eared bat. Rafinesque’s big-eared bats host a variety of ectoparasites that may be present on exposed patagium as well as in the pelage. Little data are available on the multitude of external parasites of this bat although several species of mites, fleas, flies, and ticks are believed in infect this bat. (Boyles, et al., 2011; Harvey, et al., 2011; Jones, 1977; Klug, et al., 2011; McAllister, et al., 2005; McAllister, et al., 2004)

Commensal/Parasitic Species
  • cestodes (Vampirolepis)
  • nematodes (Physaloptera)
  • nematodes (Capillaria palmata)

Economic Importance for Humans: Positive

Like most North American bat species, Corynorhinus rafinesquii is an insectivorous bat that potentially plays a role in pest control throughout its range. The presence of this bat directly contributes to the population control of several insect species groups, including mainly lepidopteran moth species. Lepidopteran moths tend to lay their eggs on woody shrubs which provide nourishment for the young while at the same time harm the woody plant species. Valuable tree species including those from the genus Pinus, Quercus, and Carya can be affected by these moths. A study by Boyles et al. (2011) predicted that the disappearance of bats in North America could lead to an estimated $3.7 billion/year in agricultural losses. (Boyles, et al., 2011; Harvey, et al., 2011; Lacki and Bayless, 2013)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Corynorhinus rafinesquii is a known carrier of the rabies virus and a fungal disease known as histoplasmosis that can be contracted by humans. No definitive figures on confirmed cases of the rabies virus being present in this bat are available. As a species that roosts in abandoned human structures, fecal accumulation containing pathogens may be hazardous to humans. However, the chance of such transference is very low. Klug et al. (2011) reported that in a study on the prevalence of rabies in bats, five Rafinesque’s big-eared bats were tested for the rabies virus and zero bats tested positive for the virus. (Boyles, et al., 2011; Harvey, et al., 2011; Jones, 1977; Klug, et al., 2011; Lacki and Bayless, 2013)

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

Currently, Corynorhinus rafinesquii is listed as a species of least concern on the IUCN red list, although previous (1996) listings report it as vulnerable. afinesque’s big-eared bats are sensitive to habitat alteration and human disturbance. With human expansion and development increasing at an alarming rate, the most detrimental impact on this species is habitat loss. An increase in logging practices that destroy roost habitats in the range of these bats poses a serious threat. This bat relies on hardwood habitats in order to maintain summer roosting habitat and foraging habitat. The main prey item of the Rafinesque’s big-eared bat is moths, which may rely on mature woody plants for larval development. These woody plants such as oak (Quercus), poplar (Populus), maple (Acer), and pine (Pinus) are commonly targeted for timber harvests.

Another concern for this species is the destruction of roost locations. In some cases, these bats roost in various human structures, such as abandoned buildings, mine shafts, and bridges. Human activity may destroy active or potential roosts. Human disturbance during hibernation periods can cause harm to these bats. Conservation strategies prohibiting human entrance into hibernacula are suggested to avoid disturbance and arousal of this species during hibernation.

Since the discovery of white-nose syndrome (WNS) in New York in 2006, populations of some bats that use cave hibernacula in eastern North America have been decimated. Rafinesque’s big-eared bats, as well as other bat species in the genus Corynorhinus, have not demonstrated susceptibility to the fungus that causes WNS. Bernard et al. (2015) reported the first confirmed case of Pseudogymnoascus destructans, the fungus that causes WNS, present on the skin of two individuals outside of a cave in Tennessee. Johnson et al. (2012) suggested that species-specific winter activity patterns such as frequent arousal from torpor along with other ecological and physiological adaptations provide defense against the harmful effects of WNS. ("Conservation and management of eastern big-eared bats", 2011; Bernard, et al., 2015; Harvey, et al., 2011; Johnson, et al., 2012a; Johnson, et al., 2012b; Jones, et al., 2003; Lacki and Bayless, 2013; Lacki, et al., 2007)

Contributors

Keifer Titus (author), Radford University - Fall 2015, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.