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Dolphin or Whale? |
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| Biologists divide cetacean groups into two suborders, the baleen whales (mysticetes) and the toothed whales (odontocetes). The suborder Mysticeti (mysticetes, or baleen whales) includes four families, six genera, and at least 13 species; while, the suborder Odontoceti (odontocetes, or toothed cetaceans) includes 10 families, 40 genera, and at least 70 species. Therefore, the groups of toothed whale are much more diverse than that of baleen whale. |
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The two suborders are distinguished by two major morphological features - presence of teeth and number of blowhole. Toothed whales have teeth and a single blowhole while baleen whales have baleen plates and two blowholes. In addition, their predation tactics are differnt. Toothed whales use echolocation to locate prey, while baleen whales are filter-feeders which do not use echolocation to prey. |
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Where do whales and dolphins live? |
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| Cetaceans live in a broad range of habitats, from major rivers and coastal areas to deep ocean. Generally, the distribution of any species is determined by the resources it needs for survival, the occurrence of which varies by season. However, several species have a very restricted distribution. For instance, the river dolphins occur largely or exclusively in some of the world's major rivers (such as the Yangtze, Ganges, Indus and Amazon rivers). Other species have a wider distribution but may be confined to one hemisphere or ocean basin. For example, the bowhead whale and the narwhal occur only in the Arctic waters, while the Gray Whale exists only in the North Pacific Ocean. |
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Whales and dolphins like in a group or alone? | |
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The social organization of different cetacean species ranges widely, from the highly complex societies of some toothed whales (e.g. Orca and Long-finned Pilot whale), to largely solitary ones of baleen whales. The social organization of any population reflects the influence of various ecological factors. The group size and social behaviour are strongly influenced by both the predation pressure and distribution of resources.
Toothed whales tend to have a more complex social organization from stable or semi-stable bonds between related individuals. This reflects not only the strategy of hunting, but also the advantages of group defense against predators such as sharks. Some are active and more acrobatic at the water surface, while some are more cryptic, showing little of themselves as they surface to breathe. |
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Most commonly seen behaviours? | |
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Cetaceans exhibit a number of behaviours: "Breaching", "Surfacing", "Porpoising" and "Blow". |
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Can whales and dolphins see clearly under water? |
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Most dolphins have excellent eyesight which allows them to see well both above and below the water. However, vision becomes of less and less value with water depth. Therefore, visual sense is ineffective under the water except at close range. |
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Instead, cetaceans detect the surroundings and communicate primarily by "echolocation", which is the production of sounds that allow an animal to orient itself and locate objects by means of the returning sound waves or echoes. The sounds made by different cetaceans are different from type, frequency and strength, therefore the sounds are unique to a specific species. |
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What do whales and dolphins eat? | |
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It is hard to generalize what preys they feed on, but a few trends can be noted. Some speices have a broad diet, while others specialize on a very limited range of prey. For instance, finless porpoises feed on squid and many different kinds of fish, while some others feed on smaller marine mammals, such as orca (Orcas do feed on sea lions). The baleen whales have evolved baleen which enables them to filter-feed planktons out of water. For example, the blue whale feeds exclusively on krill. |
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How do whales and dolphins mate? |
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Cetaceans exhibit a considerable variation in reproductive biology and mating strategies. The mating system of a species is determined by the distribution of the females, which in turn is based upon environmental constraints (e.g. availability of habitat). Male mating strategies include visual or acoustic displays to attract females. Different species of cetaceans become sexually mature at a wide range of ages, for example, the humpback whale mature by four years of age, the Indo-Pacific humpback dolphin mature at 10-12 years old, while the bowhead Whale mature at 15-20 years old. |
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Do whales and dolphins have twins? | |
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Like other large animals, cetaceans tend to produce single off-spring. Gestation is also relatively long varying from eight months of some porpoises as long as 16 months of Sperm Whale. The duration of lactation can be as long as several years in the case of some toothed whales. Prolonged lactation occurs only in species characterized by extended familial associations, such as Sperm Whale and many dolphins. By contrast, baleen whales usually wean their offspring after six to 12 months. |
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