Hammer-headed Fruit Bat
General Information

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General Information

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Figure 1: Shows the male hammer-headed fruit bat's distinct facial features.
photo courtsey of: NotTooHappy (member of www.AboveTopSecret.com)

 

Taxonomy

Categorized as an Old World Fruit Bat, the hammer-headed fruit bat also called the hammer bat and big lipped bat is the most recognizable sexual dimorphic bat in the Chiroptera, with the males being significantly larger than the females (Nowak, 1994). Males weigh between 228 to 450 g, at an average of 377 g while the females range half that size, weighing between 218 to 377g, at an average of 275 g. Males range in length between 220 to 280 mm, at an average of 250 mm. Females range in length between 195 to 225 mm, at an average of 210 mm. Males wingspan range between 686 to 970 mm, and the females's wingspan is at an average of 840 mm (Boland, 2003). The hammer-headed fruit bat is sexually dimorphic in size as well as in its facial features (Altringham, 1996). The males can be distinguished from the females by their enlarged larynx and rostrum. The males' larynx is almost three times the size of females. These structures give the males a larger and distinctive head. In addition, males have large pendulous lips with ruffle type flaps around their warty snout, and a bald split chin. In comparison, females have a more fox-shaped muzzle. Most importantly, the females lack the males' unique and enlarged facial features (Barclay, 1990). At the end of their brown ear, the furry tips are white and rounded. These species of bats have very short tails. Generally, the pelage is grey-brown or slaty-brown; with a white collar of fur that coats from shoulder to shoulder (Boland, 2003).

Figure 2: Represents the the sexual dimorphism of male and female heads, males being the larger one.
photo courtsey of:www.skullsunlimited.com

Form and Function

Only the male hammer-heads have large cheek pouches, which cover most of the face. These large pockets are used for storing food and have been reported to aid the larynx in sound production (Barclay, 1990). Remarkably, the form of the males' larynx allows the vocal apparatus to become one of the largest organs of the entire body cavity (Griffin,1958). The males' large head, enlarged larynx, and large pouches are specialized to produce rapid, loud, and sharp calls to attract females (Altringham, 1996). These bats have a large powerful tongue with three separate tips. In addition, they have adapted an oval shape patch of tridentate papillae, which are used for extracting fruit juices. The stomach and intestines of these bats are long and narrow, which permits their digestion system to digest and use all the enzymes from not only fruit but plant matter as well (Barclay, 1990). The hammer-headed fruit bat has a claw on its second finger and a large flexible thumb. This hand structure was probably adapted for grasping larger and smaller fruit (Boland, 2003). During flight their body temperatures reach a temperature from 37 to 41 degrees celsius. High ambient temperatures suit them best during flight because they have high thermal behavior, however, low ambient temperatures tends to make them lose coordination. If they ever reach an ambient temperature as low as 11 degrees celsius their flight endurance will dramatically decline. This is suggested to happen due to flight muscle relaxation and cooling (Barclay, 1990).

Figure 3: The adult male (right) and adult female (left),
notice the different snouts and body sizes.
photo pending: Jessie Cohen and JSTOR

 

This page was created by Lamar Hull for an undergraduate Animal Behavior 323 course at .

Please contact Dr. Case via email if you have and questions or comments: vecase@davidson.edu