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Pteronotus davyiDavy's naked-backed bat

By Kendra Phelps

Geographic Range

Pteronotus davyi, Davy's naked-backed bat or lesser naked-backed bat, occurs in Mexico (with the exception of the northern interior) south through Central America into coastal Columbia and Venezuela to eastern Brazil. An isolated population of P. davyi has been reported from northwestern Peru. Additionally, P. davyi occurs in Trinidad and Tobago and the Lesser Antilles. (Adams, 1989; UNEP-WCMC, 2008; Vaughan Jennings, et al., 2004; Wilson and Reeder, 2005)

Habitat

This species most commonly occupies moist to seasonally dry habitats within deciduous tropical forests along a wide altitudinal range. Less commonly, this species has been reported in open areas of mesic lowlands. Within these habitats, P. davyi may roost within man-made structures, such as houses, chicken coops, and barns, but tends to prefer the darker recesses of hot, humid caves and mines. Flyways between roosting and foraging sites are maintained along densely vegetated watercourses, with distances of up to 3.5 km between roosting and foraging sites. (Adams, 1989; Nowak, 1999; Reid, 1997; UNEP-WCMC, 2008)

  • Range elevation
    0 to 2300 m
    0.00 to 7545.93 ft

Physical Description

This species exhibits little sexual dimorphism throughout most of its range, with the exception of the most northern populations where males are significantly larger than females with regards to forearm length and several cranial measurements. A negative correlation exists between longitude and body size, with larger individuals recorded in the southern portion of the its range. The range in morphological measurements (in mm) for this species are as follows: total length, 71-85; length of foot, 9-12; forearm length, 40.6-49.6; length of ear, 16-19; length of tail, 18-25, extending two-thirds the length of the uropatagium. Mass of an adult P. davyi can range from 5-10 g. Pteronotus davyi is considered the smallest member of the family Mormoopidae.

This species has rounded wings with an average aspect ratio and low wing loading, allowing greater maneuverability in cluttered habitats. The wings are attached along the midback, covering the dorsal fur which gives the naked-backed appearance. An annual molt results in variations in pelage coloration between 2 phases, clove brown fading to a tawny brown dorsally and cinammon brown ventrally but some may appear bright ochraceous orange. Pelage is fine and densely distributed, but varies in length (8-9 mm under wings, 4-5 mm elsewhere). Short, bristle-like hairs, thought to aid in catching prey, surround the mouth. Lips are prominent, large, and can be formed into a funnel-shape, possibly used to focus echolocation emissions at a specific target. (Adams, 1989; Nowak, 1999; Reid, 1997; UNEP-WCMC, 2008; Vaughan Jennings, et al., 2004)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    6.5 to 10 g
    0.23 to 0.35 oz
  • Range length
    71 to 85 mm
    2.80 to 3.35 in

Reproduction

Female P. davyi exhibit seasonal monestrous, with mating occurring in January and February; however, limited information has been reported regarding the mating system exhibited by this species. (Adams, 1989)

Adult, female P. davyi are seasonally monoestrus, with ovulation dominated by the right ovary. Copulation typically occurs during January and February throughout most of its range; however, copulation may occur earlier in the southern portions of its range. Implantation of the fertilized egg most frequently occurs in the right uterine horn. Litter size is always one, with no reports of twins. Parturition (birth) occurs during the onset of the rainy season, coinciding with an increase in insect abundance. Lactation can continue through late July, but maturation of young is relatively rapid due to the bounty of seasonal insects.

For adult, male P. davyi, testes size fluctuates throughout the year, with greatest lengths recorded during the mating season. No baculum is present. (Adams, 1989; Nowak, 1999; Wildlife Conservation Society, 2001)

  • Breeding interval
    Breeding occurs once yearly (monestrus).
  • Breeding season
    Copulation typically occurs in January and February, but may be earlier in the southern portions of its range.
  • Range number of offspring
    1 to 1
  • Average gestation period
    60 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

No information on parental investment has been reported. However, like other bats, females invest heavily in a brief period of lactation.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female

Lifespan/Longevity

No information on lifespan has been reported.

Behavior

Typically, individual P. davyi individuals roost singly rather than in large groups. Daytime roosts may be shared with numerous other chiropteran species, but P. davyi is the dominant species in these roosts. This species frequents the darker recesses of hot, humid caves and mines, rarely roosting near an entrance.

Peaks in activity occur 2 hours after sunset and again shortly before sunrise, with a majority of individuals returning to the daytime roost between activity peaks. During cooler periods, P. davyi may only leave the roost for approximately 0.5 hour at sunset to obtain water. Flight speeds vary slightly among sexes, females average speeds of 13.1 km/h, whereas, males average speeds of 11.3 to 16.8 km/h. (Adams, 1989; Hopkins, et al., 2003; Nowak, 1999; Reid, 1997)

Home Range

No information on home range has been reported.

Communication and Perception

Pteronotus davyi individuals produce multiharmonic echolocation calls with an initially short constant frequency (CF = 67.0-68.1 kHz), followed by a downward frequency modulated sweep ending in a short segment of constant frequency (CF = 51.0-58.0 kHz). Calls lasted 4.6 to 6.7 msec, with most energy expended in the second harmonic.

This species can detect, approach, and capture 2-3 mm sized prey from a 0.5 to 0. 75 m distance in 0.5 sec. Detection to approach is characterized by an increase in the number of calls from 10-12 pulses/sec during search flight to 35 pulses/sec, followed by a burst of 200 pulses/sec immediately prior to capture. (Ibanez, et al., 1999; O'Farrell and Miller, 1997)

Food Habits

The diet of P. davyi is mainly comprised of moths (Lepidoptera), supplemented occasionally with flies (Diptera) and earwigs (Dermaptera) which are captured while foraging over water bodies. Water is consumed while in flight, referred to as drinking on the wing. (Adams, 1989; Nowak, 1999; Reid, 1997; UNEP-WCMC, 2008)

  • Animal Foods
  • insects

Predation

Roosting deep within caves and mines provides this species with some protection from most terrestrial predators, with the exception of one reported instance of a giant centipede (Scolopendra gigantea) preying on a presumably roosting individual in the interior of a Venezuelan cave. Predation on this species has only been reported one other time, in Mexico, bones from two individuals were recovered from barn owl (Tyto alba) pellets. (Adams, 1989; Molinari, et al., 2005)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Pteronotus davyi provides an essential function in the ecosystem: pest management through its insectivorous diet. In addition, this species is host to several ecto- and endoparasites. Unfortunately, little information is know about the parasites of this particular species; it is thought to harbor fewer parasites due to the high roost temperatures preferred by this species. (Adams, 1989)

Commensal/Parasitic Species
  • ticks (Carios viguerasi)
  • larval chiggers (Wagenaaria similis)
  • streblid bat fly (Trichobius species)
  • spinturnicid bat mite (Cameronieta thomasi)
  • endoparasitic nematode (Websternema parnelli)

Economic Importance for Humans: Positive

Because of their insectivorous diet, P. davyi individuals reduce the number of potentially costly agricultural pests. (Adams, 1989)

  • Positive Impacts
  • produces fertilizer
  • controls pest population

Economic Importance for Humans: Negative

Individuals of this species have tested seropositive for rabies at localities in Trinidad and western Mexico. (Adams, 1989)

Conservation Status

The destruction of habitats used as foraging sites by P. davyi potentially may endanger some populations. However, due to the undesirability of the unusually hot, humid caves preferred by this species, P. davyi roosting sites are relatively protected against human development. (Adams, 1989)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Kendra Phelps (author), Special Projects, Tanya Dewey (editor, instructor), Animal Diversity Web.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

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.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

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.

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.

forest

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

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Adams, J. 1989. Pteronotus davyi. Mammalian Species, 346: 1-5.

Hopkins, H., C. Sanchez-Hernandez, M. de Lourdes Romero-Almarz, L. Gilley, G. Schnell, M. Kennedy. 2003. Flight speeds of four species of neotropical bats. Southwestern Naturalist, 48 (4): 711-714.

Ibanez, C., A. Guillen, J. Juste B., J. Perez-Jorda. 1999. Echolocation calls of Pteronotus davyi (Chiroptera: Mormoopidae) from Panama. Journal of Mammalogy, 80 (3): 924-928.

Molinari, J., E. Gutierrez, A. De Ascencao, J. Nassar, A. Arends, R. Marquez. 2005. Predation by giant centipedes, Scolopendra gigantea, on three species of bats in a Venezuelan cave. Caribbean Journal of Science, 41 (2): 340-346.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore, MD: John Hopkins University Press.

O'Farrell, M., B. Miller. 1997. A new examination of echolocation calls of some neotropical bats (Emballonuridae and Mormoopidae). Journal of Mammalogy, 78 (3): 954-963.

Reid, F. 1997. A Field Guide to the Mammals of Central America and Southeast Mexico. New York, NY: Oxford University Press.

UNEP-WCMC, 2008. "United Nations Environment Programme, World Conservation Monitoring Centre" (On-line). UNEP-WCMC Species Database. Accessed January 17, 2008 at http://www.unep-wcmc.org/species/dbases/about.cfm.

Vaughan Jennings, N., S. Parsons, K. Barlow, M. Gannon. 2004. Echolocation calls and wing morphology of bats from the West Indies. Acta Chiropterologica, 6 (1): 75-90.

Wildlife Conservation Society, 2001. "Belize Biodiversity Information System" (On-line). Accessed January 17, 2008 at http://fwie.fw.vt.edu/wcs/BATS/050280.HTM.

Wilson, D., D. Reeder. 2005. Mammal Species of the World. Baltimore, Maryland: Johns Hopkins University Press. Accessed January 17, 2008 at http://nmnhgoph.si.edu/msw/.

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