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Orcas, sometimes called killer whales, are the largest dolphins in the world and among the most familiar marine mammals the world over. As perhaps the ocean's single most formidable predator, they link to innumerable other organisms through diet alone.
Description
Orcas, dramatically patterned in black and white, are huge animals. Bulls may reach over 30 feet in length and weigh up to nine tons; their six-foot dorsal fins, taller and straighter than those of cows and juveniles, are striking characteristics.
Diet
By virtue of their enormous range--they inhabit all the world's oceans--and complexity of behavior, orcas feed on a wide variety of prey, from squid and fish to penguins and gray whales.
Dietary Preference
In many parts of the world, orcas may be classified into discrete populations based on diet and behavior. Resident orcas, for example, tend to be coastal and fish-eating, while transients are wider-ranging and prey mainly on marine mammals and seabirds.
Formidable Prey
The orca's size and communal nature give it the capability to overpower most other marine organisms. Transient orcas will attack creatures as large as baleen whales.
Apex Predator
Like other predators at the top of the food web, orcas are particularly susceptible to ecological disruption. The whales may concentrate toxins like PCBs that are extant in the marine ecosystem.
Source:
American Cetacean Society: Killer Whale (Orca)
"Killer Whales: The Natural History ... "; John K.B. Ford, Graeme M. Ellis, Kenneth C. Balcomb; 2000
"Killer Whales of the World: Natural History & Conservation"; Robin W. Baird; 2006
More Information:
National Marine Fisheries Service: Recovery Plan for Southern Resident Killer Whales
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