The hammerhead bat (Hypsignathus monstrosus) is a flying mammal representative of the family Pteropodidae, suborder Megachiroptera, order Chiroptera. It is the only living representative of the genus Hypsignathus.
It is currently the largest bat species present on the African continent. Their activity is mainly nocturnal, they perch in the canopy made up of trees that exceed 25 meters in height. These bats form groups of less than 25 individuals when they are not in the breeding season..
In the localities where this species is found, they are quite common and frequent in wooded ecosystems with little intervention in the lowlands. In the reproductive season, males tend to always aggregate in the same places (exhibition arenas in fixed sites), so this species establishes mating “leks”.
Like other species of tropical fruit bats, these bats have an essential role in the diffusion of seeds, pollination of flowers and restoration of forest systems..
Due to this important ecosystem role, the presence of these bats in certain habitats is an indication of the conservation status of the forests. This species is distinguished by having the highest degree of sexual dimorphism among bats.
These bats are among the most sexually dimorphic species.
Males outnumber females in size and weight. Males weigh on average around 420 grams while females weigh just over 220 grams. The total head-body length, excluding the tail, ranges from 193 to 304 cm, with males being the largest..
The wingspan of these large bats can reach up to 97 cm in the largest males and a little more than 65 cm in the females..
The second premolar and all molar teeth are markedly lobed compared to other species in the Pteropodidae family..
The coloration of these bats is grayish brown or pale brown. The chest region is lighter and this coloration extends around the neck forming a short necklace. A whitish patch covers the base of the ear.
Males can be recognized in flight by their long, square, and truncated head. In addition, they have widened faces, without fur, with a thick, hammer-shaped snout, which is why they receive their common name.
Another distinctive feature of males is the presence of huge, hanging lips, which fold over the nose. Males also have an extraordinary development in their organs to emit vocalizations.
These have a pair of sacs that open on both sides of the nasopharynx. These sacs can inflate at will and function as a large enlargement of the voice box (larynx) and vocal cords..
The larynx is almost as long as half the length of the spinal column and when filled it covers most of the chest cavity, pushing the heart and other organs such as the lungs back and to the sides..
The sound produced by these bats is a continuous squawk or croak that is very powerful, to attract females over the treetops. On the other hand, females have a normal face very similar to that of the flying fox or the species of the genus Ephomophorus.
The hammerhead bat occupies a great diversity of forests, up to 1800 meters in elevation. Found in habitats including lowland tropical rainforests, riparian forests, swamps, palm forests, mangroves, and forest fragments surrounded by savanna ecosystems.
Some artificial sites have been reported in which these animals can spend the night, however, it is rare that they perch in anthropic or heavily intervened environments. They can also be seen in some caves but these habitats are little used by this species.
This species has been reported mainly in the central and western regions of equatorial Africa with a few populations to the east in Ethiopia and Kenya. Its southernmost distribution corresponds to Angola and the Democratic Republic of the Congo.
To the west the species is more common, spreading throughout much of Cameroon, Equatorial Guinea, Ghana, Ivory Coast, Gabon, Sierra Leone, Sudan, Togo and Uganda. To the north there are some populations in Burkina Faso and Guinea-Bissau.
Hammerhead bats have preferences for those breeding sites dominated by trees of the species Terminalia catappa (Combretaceae). These trees are fruit producers that greatly attract these bats, which facilitates the establishment of reproductive colonies..
They are easily located due to the specific calls that the males make on these plant formations. On the other hand, males tend to form groups or large mating leks ranging from a dozen individuals to several hundred, to make mating calls and attract females..
Mating occurs twice a year, during the dry seasons between June and August and from December to February..
Each male delimits a territory of around 10 meters in diameter from where he emits calls from the early hours of the night and early hours before dawn. The males accompany their songs with small displays of opening and flapping of their wings..
Females fly over groupings of males and eventually select one or more males to mate with. Females begin to reproduce around six months of age while males do so at one and a half years..
Most births occur between August and September, with another peak between October and December. Females give birth to a single young, however there are several reports of females giving birth to a pair of young. Each female can give birth up to twice a year because this species has postpartum heat.
These bats are mainly fruit eaters, they can consume a great variety of fruits (pulp and juice) native to the forests they occupy. The most important fruits in your diet are figs (Ficus). In addition to these, they can consume fruits of some crops such as mangoes (Mangifera), guavas (Psidium), soursop (Anonna) and bananas (Muse).
The fruits that this great bat consumes can be eaten in the same tree that produces them or they can be transported to nearby trees, where they are chewed to extract the sweet pulp..
Some authors describe some attacks on poultry such as chickens that were tied by their legs to posts or trees. However, the latter is very rare and there is not much information about these carnivorous habits..
These bats drink water by flying low over streams. When they are near the water source, they take it by sticking out their tongues and making several forays until they are satisfied..
These bats have a wide distribution range. Because of this, they are included in the category of least concern according to the IUCN, although the status of the populations of this large bat in most of its range is unknown..
The main threats to this species are the continuous destruction of its habitats and fragmentation of forests. On the other hand, these animals are chased and eliminated during their mating leks due to the amount of noise they generate. In addition to this, they are continuously hunted to be consumed as food in most of their range of distribution..
This species also turns out to be of medical importance, as it constitutes a natural reservoir for the Ebola hemorrhagic fever virus. These bats can migrate between countries which could explain the arrival of the virus to countries without previous infections such as Guinea.
According to research, the main form of infection through bats would be the consumption of their meat.
Currently, in many regions where recent outbreaks have occurred, frequent investigations are maintained on various animal groups that are natural reservoirs of this virus. Such research is intended to prevent and predict future outbreaks of Ebola hemorrhagic fever..