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Dolphins

Earth Platform > Animals > Marine Life > Dolphins
Every seven years, half of all dolphins in captivity die from marine pollution, habitat degradation, harvesting, low frequency sonar, entrapment in fishing gear and other stress-related illnesses. Luckily, a number of countries have now stopped or reduced the capture of wild dolphins, and knowledge and conditions are vastly improving. However, there are still many countries where conditions for captive dolphins are well below standards.
 

Dolphins

A lot of dolphins die in fisheries. In the North Sea alone, an estimated 10,000 harbour porpoises are killed in fishing gear each year.  In recent years there have been gear modifications  that make it possible for the dolphins, to escape once a fishingnet is closed. Not every country has made these modifications mandatory yet, so dolphins are still killed in this fishery. The dolphins killed in fishery are mainly common dolphins, spotted dolphins and spinner dolphins. Occasionally other species, including bottlenose dolphins, are caught as well, but their numbers are lower.

dolphinsEspecially in coastal areas, marine mammals are often disturbed by human activities. Collisions with boats and jet skis have already resulted in severe traumas and even deaths of marine mammals, including dolphins. Also, boat traffic in areas where dolphins usually rest or forage can disrupt their normal behaviour. The seemingly harmless human behaviour, such as swimming in areas where dolphins naturally rest, can result in disturbance and changes in behaviour. In a bay in Hawaii for example, where spinner dolphins came to rest, the increase in swimmers, has resulted in the dolphins leaving the bay. They had to find another resting area.

Dolphins are very acoustically oriented animals. With their natural sonar, they rely heavily on sound for their orientation, navigation and communication with other dolphins. Since the last century, the increase in boat traffic around the globe has resulted in a considerable increase in noise in the world's oceans. This has a negative effect on dolphin and whale navigation and communication. 

 

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Dolphins in the news

Dolphins and Whales News -- ScienceDaily

Narwhals and belugas can interbreed - A team of researchers has compiled the first and only evidence that narwhals and beluga whales can breed successfully. DNA and stable isotope analysis of an anomalous skull from the Natural History Museum of Denmark has allowed researchers to confirm the existence of a narwhal-beluga hybrid.
Dolphins form friendships through shared interests just like us, study finds - When it comes to making friends, it appears dolphins are just like us and form close friendships with other dolphins that have a common interest. The research provides further insight into the social habits of these remarkable animals.
New sub-species of pilot whale identified in Pacific Ocean - Short-finned pilot whales are found over a wide swath of the world's oceans, with habitats in the Indian, and Pacific, and North Atlantic oceans. Despite this wide distribution, the whales have been recognized as a single species -- but a recent study has found that two unique subspecies actually exist.
Climate driving new right whale movement - New research connects recent changes in the movement of North Atlantic right whales to decreased food availability and rising temperatures in Gulf of Maine's deep waters. Right whales have been showing up in unexpected places in recent years, putting the endangered species at increased risk. The study provides insights to this key issue complicating conservation efforts.
Dolphin ancestor's hearing was more like hoofed mammals than today's sea creatures - Paleontologists are looking into the evolutionary origins of the whistles and squeaks that dolphins and porpoises make -- part of the rare echolocation ability that allows them to effectively navigate their dark environment.