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In May 2005 , researchers in Australia discovered a cultural aspect of dolphin behaviour: Some dolphins (Tursiops aduncus) teach their offspring to use a tool. The animals break off sponges and put them onto their mouths thus protecting the delicate body part during their hunt for fish on the seabed. Other than with primate simians , the knowledge to use a tool is mostly handed over only from mothers to daughters. The technology to use sponges as mouth protection is not genetically inherited but a taught cultural behaviour.
In captivity, many dolphins seem to have committed suicide . They either do so by repeatedly slamming their head against the pool walls or other solid objects or simply by not coming up for air anymore. Probably one of the best known cases of dolphin suicide is that of a dolphin named Cathy, one of the bottlenose dolphins that performed in the television series Flipper . She most likely died of self induced asphyxiation in the presence of her trainer Richard O'Barry .
Senses
Most dolphins have acute eyesight both in and out of the water and their sense of hearing is superior to that of humans. Though they have a small ear opening on each side of their head it is believed hearing underwater is also if not exclusively done with the lower jaw which conducts the vibrations to the middle ear via a fat filled cavity in the lower jaw bone. Hearing is also used for echolocation which seems to be an ability all dolphins have. The dolphin's sense of touch is also well-developed.
However, they seem to lack a well-developed sense of smell , but they most likely can taste and do show preferences for certain kinds of fish. Since dolphins spend most of their time below the surface in the wild, just tasting the water could act as a sense of smell. |
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Feeding
Dolphins are predators, chasing their prey at high speed. The dentition is adapted to the animals they hunt: Species with long beaks and many teeth forage on fish , whereas short beaks and lesser tooth count are linked to catching squid. Some dolphins may take crustaceans. Usually, the prey is swallowed whole. The larger species, especially the orca , are capable of eating marine mammals, even large whales. There are no known reports of cannibalism amongst dolphins.
Individual species may employ a number of methods of hunting:
- Herding - where a superpod will control a school of fish while individual members take turns plowing through the herd, feeding.
- Corralling - where fish are chased to shallow water where they are more easily captured.
- Fish Wacking - where the dolphin uses its fluke to strike the fish, stunning it and sometimes sending it clear out of the water.
- Stunning - using the echolocation melon, very loud clicks are directed at prey, stunning them.
- Foraging - A recent study reported that wild bottlenose dolphins ( Tursiops ) in Western Australia use sponges to forage in the sea bed for food.
Individual species may employ a number of methods of hunting, but even within a species various feeding methods may be employed, some being used by only a single dolphin population. Fish and squid are the main source of food for most dolphin species, but the False Killer Whale and the Killer Whale also feed on other marine mammals.
One feeding method employed by many species is herding, where a pod will control a school of fish while individual members take turns plowing through the school, feeding. The tightly packed school of fish is commonly known as bait ball. Coralling is a method where fish are chased to shallow water where they are more easily captured. In South Carolina, the Atlantic Bottlenose Dolphin takes this one step further with what has become known as strand feeding, where the fish are driven onto mud banks and retrieved from there.[17] In some places, Orcas will also come up to the beach to capture seals. Some species also whack fish with their fluke, stunning them and sometimes sending fish clear out of the water.
Reports of cooperative human-dolphin fisheries date back to the ancient Roman author and natural philospher Pliny.[18] A modern human-dolphin fishery still takes place in Laguna, Santa Catarina, Brazil.[19]
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