The Giant kingfisher bat (Pteropus alcedinidus) is a member of the Pteropodidae family, of the order Chiroptera (bats). Members of this family are commonly referred to as megabats or fruit bats, and are characterized by their relatively large size. Like most bats in the Pteropodidae family, the Giant kingfisher bat has lost the ability to echolocate, and relies instead on its sight for locating food. Its diet consists mainly of fish that live in the mangroves and coast of the Malay Archipelago, but usually supplements it with fruit during the weeks previous to the mating season.
This species is unique among bats because it is the only one that dives into the water for catching its prey. Its unusual beak-shaped snout, which resembles the beak of a kingfisher, provides streamlining and minimizes the impact against the surface to avoid displacing water and scaring away fish. Unlike most mammals, which have seven cervical vertebrae, the Giant kingfisher bat has five cervical vertebrae and they are surrounded by thick layers of soft tissue. This gives the bat a shorter neck with a shock absorption mechanism that greatly reduces the risk of injury when penetrating the water.
Pteropus alcedinidus has also developed a series of adaptations for navigating underwater during short periods of time. Its nostrils and reduced ears close underwater, and due to having its eyes protected by a full nictating membrane it mostly relies on its highly sensitive long whiskers for detecting its prey or other obstacles. Nonetheless, this species has good vision on land and uses it for detecting potential prey and fruit instead of echolocation, which has been lost in favor of smaller ears that provide better streamlining.
In order to catch fish, the Giant kingfisher bat soars over the water taking advantage of the high aspect ratio of its wings to save energy. When it localizes its prey, the bat plunges into the water and uses its sensitive whiskers to catch it. In order to move towards the surface, special fibers in the patagium or wing membrane of the bat get harder and serve as a paddle to displace water more efficiently. The unusually high number of mitochondria in its cells, along with a highly vascularized tissue, enable the bat to power its muscles to rise to the surface and fly into the sky once again.