Orcas, or killer whales, are highly sociable and intelligent whales and for that reason are often seen in marine aquarium parks and shows (such as the whale pictured above at SeaWorld in Florida). There are three to five types of orcas that are considered different enough to be different races.
Killer whales are found in all oceans and most seas, though their migration patterns are poorly understood. The largest population of orcas is believed to live in the Antarctic ocean.
Orcas have a variety of prey, including about 30 species of fish such as tuna and salmon. Sharks, sea turtles, seals and squid are also eaten by killer whales. Killer whales are sometimes referred to as the wolves of the sea, because they hunt in groups.
Orcas do not have any natural predators, though because they are top predators they are at a higher risk for certain threats, one being bioaccumulation. Bioaccumulation is the process by which toxins become more concentrated as they travel up the food chain, i.e. from a fish to a seal to a whale. Marine debris also impacts orcas because they can consume prey that have consumed plastic, or become entangled in fishing nets. Oil spills also obviously pose a threat to killer whales because of the negative impacts they have on their prey and habitat.
Some subspecies of orcas are listed as endangered, though not all killer whale species are considered endangered. It is recognized that there is not enough data on each species to determine how healthy each population of orcas is.