MammalMAP: Bottlenose dolphin
These highly intelligent animals are grey in colour, typically 2 – 4 metres long and weigh between 300 – 500 kgs. These dolphins have short, well developed snout that resembles an old fashioned gin bottle – the source of its common name. This snout houses 18 – 28 conical teeth on each side of the jaw allow the dolphin to grasp its prey while its tongue manoeuvres the prey item down its throat.
The diet of bottlenose dolphins is broad and varies according to region. However, their diet primarily consists of fish, crustaceans and squid. Dolphins are team players and live in social groups called pods. Once a shoal of fish is found, typically by echolocation (a type of sonar), dolphins work together to herd the fish together and maximise the number of prey from the hunt.
Another feeding strategy is ‘strand feeding’ where dolphins chase their prey to shore and knowingly strand themselves to feed. Bottlenose dolphins are the poster children of interspecies cooperation. Fishermen and dolphins work together in the town of Laguna, Brazil. A pod of bottlenose dolphins would drive fish toward fishermen standing in shallow waters. One dolphin rolls over and the fishermen throw out their nets. The dolphins feed on the escaping fish. These dolphins were not trained to do this and this collaboration began before 1847. This behaviour has been noted in other places around the globe.
Coastal and island-centred populations are especially vulnerable to hunting, incidental catch, and habitat degradation (Source IUCN). Worldwide reports indicate that dolphins are caught for bait, human consumption, or to remove competition in the fishing industry. Drive fisheries have been reported for the Faroe Islands and Japan. The average catch rate in Japan was 594 dolphins per annum from 1995–2004.
Dolphins have captured the minds and hearts of people for centuries due to their altruistic behaviour. How often do we hear tales of dolphins saving surfers from sharks? It’s practically cliché at this point. They are also known to help other animals who find themselves in trouble. Militaries have trained these dolphins for wartime tasks such as mine detection and locating enemy divers. And researchers are still developing new tests in attempts to determine the intelligence of the dolphins.
All in all, it seems that we are still fascinated with these dolphins. And based on interactions between our two species (both historic and current), the feeling is mutual.
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