Noctilio albiventris - The Lesser Bulldog Bat​

Physical Description:

Noctilio albiventris is brown with orange on the neck and shoulders (Eisenberg 1989). It has a bulldog like face from which it derives it name and has drooping lips with jowls that expose its canines and pointed upper incisors (Emmons 1990). The lips appear swollen and the muzzle is pointed. The upper lip is smooth but divided by a vertical fold of skin. The bottom lip has a wart like skin cluster and the chin has semicircular folds of skin on it. N. albiventris is characteristic of having a protruding nose and nostrils that open forward and downward. No nose excrescences or nose leaf is associated with this bat. The cheeks are elastic and the ears are large, slender, pointed, and separated. This bat also has a tragus with a serrated outer margin (Nowak 1999). Males are more orange than females and have pointed wings. The dental formula is I 2/1, C 1/1, P 1/2, M 3/3 = 28 and this bat is associated with having a strong penetrating odor (Nowak 1999 and Eisenberg 1989). It has greatly enlarged claws on its feet including a relatively large calcar and uses it to catch insects (Nowak 1999). The average weight of a male is 28.7 grams and 23.0 grams for a female. The average length for a male is 74.9 mm and 71.6 mm for a female (Eisenberg 1989). N. albiventris is smaller than its sister species N. leporinus and has higher frequency echolocation calls (Kalko 1998). ​

Distribution:

The distribution of the Noctilio albiventris ranges from southern Nicaragua to northern Argentina and from Uruguay to the Greater and Lesser Antilles (Eisenberg 1989). Higher concentrations of Noctilio albiventris are found in Neembucu, Bajo Chaco, Matogrosense, and Campos Cerrados, in descending order. N. albiventris can sustain different habitats but its primary habitat is like that of Neembucu which primarily consists of inundated wetlands and vest grasslands in flat, low terrain with slow moving rivers. The Bajo Chaco is also an area with high N. albiventris concentrations and is characteristic of having extensive palm savannas, interspersed with medium-height scrub forests and is slightly elevated. Slow flowing rivers are also common for this area. All areas with greater N. albiventris concentrations are characteristic of having medium to high precipitation and semi- to sub-humid conditions (Willig, Presley, Owen, and Lopez-Gonzalez). N. albiventris generally inhabits lower elevations and tolerates many different types of trees and foliage for roosting. Its foraging areas range from evergreen forests to croplands (Eisenberg 1989).

Ontogeny and Reproduction:

Males deposit their sperm in late November and December while the females are still in hibernation. The female experiences delayed implantation in which the sperm can not penetrate even though the follicle is present during copulation. Females are able to store sperm in the uterus and oviducts for weeks or months until one to three days after awaking form hibernation. When the female gives birth in late April or early May, a single offspring results and is nursed for three months (Nowak 1999 and Eisenberg 1989).

Ecology and Behavior:

Noctilio albiventris has its first eating frenzy at dusk, approximately 30 minutes after the sun sets and the activity remains high for an hour to an hour and a half. The foraging activity then tapers off to two to three bats per ten minutes (Kalko 1998). There is also a second frenzy after midnight though the bat foraging is not as high as with the post dusk foraging (Eisenberg 1989). It captures insects in mid-air, termed aerial captures, from the water surface, termed pointed dip, and occasionally dragged its feet through the water's surface catching minnows, termed directed random rake. Although N. albiventris eats minnows, it only does so on very rare occasions and doing so is almost uncharacteristic of this bat (Kalko 1998). This bat roosts in hollow trees, foliage or in houses and usually nests in large groups of approximately 300 individuals within a hollow tree (Fenton, Audet, Dunning, Long, Merriman, Pearl, Syme, Adkins, Pederson, and Wohlgenant 1993). It eats water beetles as well as other small insects, which it captures with its uropatagium or tail scoop. It then retrieves the prey by lowering its head to its uropatagium and stores the prey in its large cheek pouches (Kalko 1998).

            The albiventris is agile and circles back and forth in one area when hunting and then moves to another. Traditionally it forms a figure eight pattern when searching for prey over water (Kalko 1998). It also normally forages in small groups of eight to fifteen members and forages mostly over still water but will also search for prey in fields (Nowak 1999).

            N. albiventris flaps at about four wing-beats per second and travels at speeds between seven and seven and a half meters per second. As this bat approaches its prey, its speed is reduced to one to two meters per second. N. albiventris searches for prey at greater heights and only descends to low search heights for two to five meters before returning to high search flight (Kalko 1998).

            For echolocation, the Noctilio bats use a system that is specific for catching prey close to the water. These bats produce CF signals that are interspersed with mixed signals made of steep FM and CF components. The CF components are used to detect prey in front of water. This is because water can produce a significant amount of clutter background noise. When approaching its prey, pulse interval and pulse duration are reduced and the CF component is eliminated. Short FM components are also changed by being emitted at high repetition rates (duration is 2ms at 150-170 hertz). This bat does not overlap the emitted signals with the echoes returning from the prey and it ceases all signals when the bat is 15-20 centimeters from its prey (Kalko 1998).   

Literature Cited:

Roverud, -R.C. "Complex Sound Analysis of the Lesser Bulldog Bat: Evidence for a Mechanism for Processing Frequency Elements of Frequency Modulates Signals Over Restricted Time Intervals." Journal of Comparative Physiology A Sensory Neural and Behavioral Physiology. 174 (1994): 559-565.

Fenton, M.B., D. Audet, D.C. Dunning, J. Long, C.B. Merriman, D. Pearl, D.M.Syme, B.Adkins, S. Pedersen, and T. Wohlgenant. "Activity Patterns and Roost Selection by Noctilio Albiventris (Chiroptera: Noctilionidae) in Costa Rica." Journal of Mammalogy. 74 (1993): 607-613.

Kalko, Elizabeth K.V., Hans Ulrich Schnitler, Ingrid Kaipf, Alan D Grinnell. "Echolocation and Foraging Behavior of the Lesser Bulldog Bat, Noctilio albiventris: Preadaptations for Piscivory?" Behavioral  Ecology and Sociobiology. 42 (1998) 305-319.

Nowak, Ronald M., Walker's Mammals of the World. 6th ed. Baltimore: 1999.

Eisenberg, John F., Mammals of the Neotropics. Vol.1. Chicago and London. 1989. 4 vols.

Neweller, Gerhard. The Biology of Bats. Trans. Ellen Covey. New York. 1993.

Emmons, Louise H., Neotropical Rainforest Mammals, A Field Study Guide . Chicago and London. 1990

Reference written by Keith Dallenbach, Biology 378 (Mammalogy), University of Wisconsin – Stevens Point.  Edited by Christopher Yahnke. Page last updated August 15, 2005.