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The fishing bats of the world don’t quite conform to the standard stereotype of the flying mammals belonging to the Order Chiroptera—that is, a minuscule creature wheeling about at dusk to snag mosquitoes or moths out of the darkening sky. These specialized hunters swoop down upon small fish and other aquatic organisms in the manner of miniature ospreys or bald eagles. Only a few bats of the thousands of described species are known to regularly hunt fish. These include representatives of the vesper-bat family, such as the long-fingered bat of Eurasia and the fish-eating bat of Mexico, as well as two kinds of noctilionid bats: the greater and lesser bulldog bats of the Neotropics. Read on for more facts about fishing bats and their interesting behavioral patterns and diet.
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A Unique Diet
Most bats are insectivores: Many use echolocation to pursue flying insects like moths on the wing. Others are nectar-eaters, performing essential pollination duties for various kinds of flowering plants. The largest of the world’s bats, the so-called flying foxes, feast both on fruits and nectar. Along with species that drink the blood of large mammals (the well-known vampire bats), frog-eating bats and others that occasionally target songbirds, fishing bats have some of the most unique diets—piscivorous, technically—of the order. Rarely do fishing bats prey exclusively on fish: The long-fingered bat, for example, hunts aquatic insects part of the year, and the fish-eating bat may actually feed more heavily on crustaceans.
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One obvious fact about fishing bats is that most exhibit morphological traits that assist them in catching fish and other aquatic creatures. They tend to have relatively longer legs and hind feet than other bat species. According to the US Virgin Islands Division of Fish and Wildlife, for example, the clawed feet of the greater bulldog bat may be nearly four times as big as those of bats that don’t prey upon fish. The greater bulldog bat and some other piscivorous species like the fish-eating bats also have specialized tail and rear-membrane structures that allow their legs and claws to sieve freely at the surface of the water to snag small fish.
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The US Virgin Islands Division of Fish and Wildlife describes the hunting habits of the greater bulldog bat. The foraging bat cruises within a few feet of the water’s surface, employing echolocation to identify the ripples that might betray a feeding fish. To capture its prey, the bat will then drop lower and runs its claws through the water. It may consume the fish on the wing or roost with it somewhere nearby. A 2008 study published in the Dartmouth Undergraduate Journal of Science investigated bulldog-bat foraging behavior in Costa Rica’s Rio Sirena Lagoon. The researchers suggested the bats preferred upstream hunting because calmer water there, beyond the most intense roiling of tidal currents, better served their echolocation--and possibly helped them avoid competition with and predation from aquatic hunters like bull sharks and American crocodiles.
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Another little know facts of fishing bats, is that they are sensitive to a variety of environmental changes. Water pollution, for example, may affect them in the same manner it affects any higher-level aquatic predator. Habitat loss is also a major issue. The bats suffer not only from hydrological diversions and impoundments affecting their hunting grounds, but also from human intrusion into their roosting caves and crevices. Such highly specialized species as the island-dwelling fish-eating bat of Mexico also faces threats from introduced, non-native animals like rats.
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(1) First Fishing Bat Discovered in Europe; Kate Ravilious; National Geographic News; November 2010
(2) U.S.V.I. Dept. of Planning & Natural Resources - Division of Fish & Wildlife: Fishing Bat
(3) Research: Foraging Behaviors in Fish-eating Bats; Kaplan et al.; Dartmouth Undergraduate Journal of Science; Nov. 2008
(4) IUCN Red List of Threatened Species: Myotis vivesi