Pteronotus davyi
Davy's naked-backed bat

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)

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)

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)

No information on lifespan has been reported.

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.

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)

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)

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)

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)

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

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

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)