Earth Talk - Little is known of hard-to-track orcas
Orcas are very susceptible to pollution, due to their place at the top of the ocean food chain. But little is known of their habits since they're hard to track.
蚕:听听 How are populations of the world鈥檚 orca whales faring these days?
鈥� J. Witham, Bangor, Maine
础:听聽聽 The largest member of the dolphin family and a major draw at marine parks, orcas (also known as 鈥渒iller whales鈥�) are highly intelligent and social marine mammals. Many of their habits are still a mystery to science, as the great black-and-white creatures, which can grow to 26 feet and weigh six tons, are fast-moving and difficult to track.
Given this uncertainty, the International Union for the Conservation of Nature (IUCN), a nonprofit group that maintains a frequently updated global list (the so-called Red List) of endangered and threatened wildlife, merely lists the status of orcas as 鈥渄ata deficient.鈥� IUCN is currently involved in an assessment of orca populations around the world to determine what their status should be.
Orcas may not have a clear-cut conservation status internationally, but the US government is concerned enough about the animals that ply the waters of Washington鈥檚 Puget Sound and San Juan Islands to put them on the federal endangered species list. Chief among threats to orcas is loss of their food supply, mostly West Coast salmon populations destroyed by hydroelectric dams and other human encroachment. Habitat loss, chemical pollution, captures for marine mammal parks, and conflicts with fisheries have also played roles in the decline of the Northwest鈥檚 orcas.
According to the National Marine Fisheries Service, the southern resident orca population has fluctuated considerably since researchers began studying it in earnest some three decades ago. In 1974 the group comprised 71 whales, but spiked to 97 animals by 1996. Since then, the population has fallen below 80.
Due to their voracious appetites and their place at the top of the ocean food chain, orcas are very susceptible to pollution and chemicals. For this reason, many scientists consider orcas an 鈥渋ndicator species,鈥� one that reflects the health of marine ecosystems in general. If orcas are in decline, the rest of the ocean may be in trouble, too.
Increased concern about the health of marine ecosystems in recent years is good news for orcas, which are dependent on a wide range of fish and marine mammals for sustenance. The preponderance of protected stretches of both ocean and coasts gives orcas a boost in their struggle to stay one step ahead of extinction.
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