Hammer-headed bat

The hammer-headed bat (Hypsignathus monstrosus), also known as the hammer-headed fruit bat, big-lipped bat, and hammerhead bat, is a megabat found across West and Central Africa. It is the largest bat in continental Africa, with wingspans nearly reaching 1 m (3.3 ft). Males are almost twice as heavy as females and look very different, making this one of the most sexually dimorphic bat species in the world.

These bats eat mainly fruits such as figs, bananas, and mangoes, and they sometimes eat other foods. Females often follow the same paths to find fruit, while males search for the best-quality fruit. They fly out at night to find food and rest in trees during the day, sometimes alone or in small groups. Unlike many bats, both males and females rest together.

Mating happens in two seasons each year during the dry months. These bats are special because they use a system called lek mating. Males gather in one place, like along a river, and make loud, honking calls to attract females. Females choose a male to mate with, and only a few males are chosen most often. Babies are born five or six months later, usually one at a time.

Taxonomy and etymology

The hammer-headed bat was first described in 1861 by a scientist named Harrison Allen. He placed it in a new group called Hypsignathus. The name comes from Ancient Greek words meaning "high" and "jaw," referring to the bat's special mouth shape. The species name monstrosus means "like a monster" in Latin.

A study in 2011 showed that Hypsignathus is an early member of a group of bats called Epomophorini, which also includes Epomops, Micropteropus, Epomophorus, and Nanonycteris. Originally, the hammer-headed bat was thought to belong to a group called Pteropodinae, but later it was moved to another group called Epomophorinae. Some scientists still place it in yet another group called Rousettinae.

Description

The hammer-headed bat is the largest bat in mainland Africa. Males can have wingspans up to 90.1 cm (2.96 ft), and both males and females have forearm lengths longer than 112 mm (4.4 in). Males are much larger than females, sometimes up to twice as heavy. Males often make loud, honking sounds and have very large voice boxes, bigger than females', which take up a lot of space in their bodies.

Both males and females have dark brown fur, with lighter fur on the sides and back of the neck. Males have big heads with huge lips, while females have narrower faces. Both have large eyes and triangular ears. They have 28 teeth, but sometimes an extra tooth on each side, making 30 teeth total. Their wings are brownish and attached to their hind legs, and they do not have tails.

Distribution and habitat

The hammer-headed bat lives in low areas, never higher than 1,800 meters above sea level. It is most often found in rainforests, including areas near swamps and rivers, as well as places where forests mix with grasslands. Though sometimes seen in savanna areas, these sightings are uncommon, and it is thought that these bats may just be traveling through. This bat can be found across a large area of West and Central Africa, including countries such as Angola, Benin, Burkina Faso, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Nigeria, Sierra Leone, Sudan, Togo, and Uganda.

Biology and ecology

Hammer-headed bats eat mostly figs, but they also enjoy mangos, bananas, and guavas. Like all fruit-eating animals, they need to find ways to get enough protein. These bats have longer intestines to help them get more nutrients from their food.

Males and females hunt food differently. Females follow set paths to find reliable food, even if it isn’t the best quality. Males travel farther, up to 10 kilometers, to find areas with lots of fruit. They eat the fruit on the tree or carry it away, chewing it to enjoy the juice and soft parts while spitting out the rest. Their waste often contains seeds, showing they help spread plant seeds.

Not much is known about how these bats have babies. In some places, they have two breeding times each year during the dry seasons. After about five to six months, females give birth to one baby at a time, though sometimes twins are born. Baby bats weigh about 40 grams when they are born. Females can have babies after six months, while males take eighteen months to be ready to have babies.

Males of this species gather in special areas called leks during mating time. Here, they show off by honking and flapping their wings. Females choose a male and stay with him for a short time before leaving. Most of the males in the center of the lek are chosen by females. In other places, these bats use a different way to choose mates, called a harem system.

During the day, hammer-headed bats rest in trees high above the ground. They often rest alone but sometimes in small groups. They sleep with their noses covered by their wings and only meet up at sunset to clean themselves before going to find food. These bats hide to stay safe from animals that might want to eat them. They also have to deal with tiny parasites that live on them.

Interactions with humans

The hammer-headed bat sometimes damages fruit crops because it eats fruit. Because it can make very loud sounds at night, some people think it is a big problem.

People in places like Nigeria and the Democratic Republic of the Congo sometimes hunt and eat these bats. Scientists have studied these bats to see if they might carry a virus, but they have not found clear proof that these bats cause sickness in people.

As of 2016, these bats are not in danger and are considered to be doing well overall. They live in many places and have large populations. Some zoos have kept them, but they can get sick when moved to new places.