Hammer-headed Bat - Ecology and Behavior

Ecology and Behavior

Hammer-headed bats are frugivores. Figs make up much of their diet, but they may also include mangos, bananas and guavas. There are some complications inherent in a fruit diet such as insufficient protein intake. It is suggested that fruit bats compensate for this by possessing a proportionally longer intestine compared to insectivorous species. This enhances their ability to absorb protein. They also have very rapid digestive systems allowing these bats to assimilate high amounts of fruit to ensure that adequate protein is absorbed. It is also suggested that by eating a wide variety of fruits with varying protein contents, fruit bats are able to maintain an entirely frugivorous diet.

Generally fruit is picked and taken to a nearby tree where it is chewed, the juice squeezed out and the pulp discarded. Since they often do not consume the pulp, these bats are not considered to be good seed distributors. Males may forage long distances (up to 10 km) to locate the highest quality food. Females rely on established feeding routes that offer a constant supply of lower quality food. This may reflect different metabolic requirements based on body size differences.

Large bats often experience difficulties with overheating during flight. The limited thermoregulatory capabilities of flying bats appears to be one factor closely associated with why flight activity primarily occurs during cooler nocturnal temperatures. It has been found that hammer-headed bats are able to tolerate higher ambient temperatures during flight than other bats. This ability is associated with this bat’s high thermal conductance (C_f) which is defined as the total heat loss less the heat loss due to evaporation divided by body temperature less the ambient temperature (C_f = /). However, they are especially sensitive to ambient temperatures below 11°C and a decrease in flight coordination is seen. Due to the large surface area of the wing, convective heat loss to cool air may be significant enough to chill flight muscles preventing the precise coordination essential for flight.

These bats are nocturnal, roosting during the day in the forest canopy. They rely on camouflage to hide them from predators. Specific species of trees are not selected for roosting, however some roosts may be used for long periods of time. Roosts are generally 20–30 meters from the ground.

The main predators of this species are humans and nocturnal and diurnal birds of prey. However, infection by parasites is often the most significant problem for the hammer-headed bat. Adults are often infected with mites and the hepatoparasite, Hepatocystis carpenteri.