Greater bulldog bat (Noctilio leporinus)
|Also known as:||fisherman bat, fishing bat, greater fisherman bat, greater fishing bat, Mexican bulldog bat|
Classified as Least Concern (LC) on the IUCN Red List (1).
The greater bulldog bat is one of the largest bats in the New World (4) (6), and also one of the most distinctive. One of only a few bat species to feed on fish, it is highly specialised for this lifestyle, with long hind legs, greatly enlarged hind feet and formidable sharp, curved claws which are ideally adapted to capturing its slippery prey (2) (4) (5) (6) (7). The muzzle is long, and the upper lip is split and drooping, while the chin is ridged with folds of skin, giving the bulldog-like appearance for which this bat is named (2) (4) (5) (6) (8). Although lacking a noseleaf, the nose does have a conspicuous, forward-projecting fleshy pad (2) (4) (5) (6). The ears are long, narrow and pointed (2) (4) (6) (8), and are furred only at the base (5). The fur of the greater bulldog bat is very short, and quite variable in colour, ranging from bright reddish-orange to chestnut brown, yellowish or greyish-brown, and there is a pale stripe down the middle of the back. The underparts are paler (2) (4) (5) (6) (8). The sides of the lower back are naked, and the wing and tail membranes are brown. The tail membrane is quite long, while the tail itself is shorter than the membrane, but its tip protrudes from the membrane’s upper surface (2) (4) (5) (6).
Male greater bulldog bats are larger than females (5) (6), and are usually a brighter orange colour, whereas females tend to be duller grey or brown (2). This species shows considerable variation in size across its range (5) (8), with some scientists recognising three subspecies (4) (5). The greater bulldog bat can be distinguished from the only other Noctilio species, the lesser bulldog bat (Noctilio albiventris), by its larger size and more well-developed hindlimbs, feet and claws (2) (5) (6) (7). Both species are reported to have a particularly strong, musky odour (2) (3) (4) (6).
The greater bulldog bat is widespread across Central and South America and the Caribbean, occurring from Sinaloa in Mexico, south to northern Argentina and south-eastern Brazil. In the Caribbean, it occurs on the Greater and Lesser Antilles and in the southern Bahamas (1) (2) (4) (5) (6). However, it is somewhat patchily distributed across its range, being restricted mainly to non-arid lowland and coastal areas, and along major river systems (4) (5) (8) (9).
This species is found in tropical lowland habitats, particularly around lakes, ponds, quiet streams and rivers, as well as estuaries, bays and lagoons along the coast (5) (6) (7) (8) (9). It roosts in hollow trees, caves, rock fissures and sometimes buildings, and occasionally shares roosts with other bat species (2) (4) (5) (6) (9).
Perhaps best known for its habit of hunting fish, giving it the alternative name of ‘fishing bat’, the greater bulldog bat typically forages over water, using echolocation to detect the ripples made by fish as they disturb the water’s surface (2) (3) (4) (5) (6). The long legs and long, sharp claws are used to skim the water and snatch up prey from just below the surface. The prey is then quickly transferred to the mouth, with the tail membrane brought up under the body to prevent it being dropped, and is either eaten in flight or stored temporarily in cheek pouches and carried to a perch to be consumed (2) (4) (5) (6) (7). The greater bulldog bat may consume as many as 30 or 40 fish in a night, capturing prey up to 10 centimetres in length, and will also take insects, shrimps, crabs and scorpions (2) (3) (4) (6) (7). As well as from water (including the sea), prey is also sometimes taken from the ground or in the air (4) (6), although insects caught in the air are captured in the wing or tail membranes rather than with the feet (2) (4). If knocked into water, this species is able to swim well, and can even take off from the water (2) (7).
The greater bulldog bat may forage in small groups of around 5 to 15 individuals (1) (2) (6), and during the day will roost in colonies that sometimes number into the hundreds (1) (4) (5) (9). Within the roost, the bats cluster into small ‘harem’ groups, typically consisting of two to nine adult females and a single adult male. Bachelor males roost separately, either alone or in small groups (4) (9) (10). The harems are quite stable in composition, often occupying the same roost site over many years, but the group is usually taken over by a new male every two years or so (4) (10). Interestingly, females from the same roost group often forage together, while males usually forage alone (4) (10).
The greater bulldog bat usually gives birth once a year, to a single young at a time, but in some areas breeding may occur twice in the same year (4) (5). The breeding season varies with location, usually coinciding with peak food availability. Pregnancies have been reported between September and January in some regions, with young suckled in November to April (2), while others report breeding to begin in November and December, with births occurring from late April to June (5). Females may form ‘nursery colonies’, gathering together to give birth (2) (8). The young bats fly for the first time at around 1 to 2 months old (4) (5), and the species may live for up to 11 years in captivity (2) (4).
The greater bulldog bat has a large population and widespread distribution and is not currently known to face any major threats (1). However, there are fears that this bat may come under increasing pressure in the future, for example from water pollution, or from changes to water levels or river flow, which may also affect its prey (1) (9). The species is also killed by fish farmers in some areas (1). Perhaps the greatest potential threat, however, is the loss and degradation of waterside habitats, which provide important roost sites (1) (9). Despite being widespread, the greater bulldog bat does not occur at high densities, and this, together with its unique feeding strategy and its specific habitat requirements (suitable roost sites close to open, relatively still water), may increase its vulnerability to these various threats (9).
Although the greater bulldog bat is not legally protected throughout most of its range (9), it is found in a number of protected areas (1). In light of the potential future threats to this species, conservation measures have been recommended to prevent population declines. These include protection of suitable habitat, further studies into the species’ ecology in mainland South America, and the protection of key roost sites, particularly in areas where the bat has a more restricted distribution or isolated populations. As a large, distinctive species, the greater bulldog bat is a good candidate for monitoring programmes, the results of which may also have important implications for the other species which share its watery habitat (9).
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- Echolocation: detecting objects by reflected sound. Used by bats and odontocete cetaceans (toothed whales, dolphins and porpoises) for orientation and to detect and locate prey.
- Noseleaf: a fleshy structure surrounding the nose, common to many bats. It is believed to function in focusing echolocation calls (high-pitched calls used in orientation and to locate prey) emitted from the nose.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
IUCN Red List (July, 2010)
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