1. Killer whale or orca?
According to the book Whales and Dolphins in Question, the name killer whale originated with whalers, who called the species "whale killer" because of its tendency to prey on whales along with other species such as pinnipeds and fish. Over time, perhaps because of the whale's tenacity and ferocity in hunting, the name was switched to killer whale.
So, where's orca from? The term orca comes from the killer whale's scientific name, Orcinus orca. Orca is Latin for "a kind of whale." Because wild killer whales are not a threat to humans, and the term "killer" has a derogatory tone, many people now refer to these whales as orcas, rather than killer whales. At least in the U.S., and even among whale researchers, killer whale still seems to be used more commonly, although I've used both terms in this article.
Yes, killer whales are dolphins, which are toothed whales. All killer whales have teeth on both their top and bottom jaws - 48-52 teeth in total. These teeth can be up to 4 inches long. Although toothed whales have teeth, they don't chew their food - they use their teeth for capturing and tearing food. Young killers whales get their first teeth at 2-4 months of age.
Orcas may work in pods to hunt their prey, and have a number of interesting techniques to hunt prey, which include working together to create waves to wash seals off ice floes, and sliding onto beaches to capture prey.
4. There is more than one type of killer whale.
Killer whales were long considered one species - Orcinus orca, but now it appears that there are several species (or at least, subspecies - researchers are still figuring this out) of orcas. As researchers learn more about orcas, they have proposed separating the whales into different species or subspecies based on genetics, diet, size, vocalizations, location and physical appearance.
In the Southern Hemisphere, proposed species include those referred to as Type A (Antarctic), large type B (pack ice killer whale), small type B (Gerlache killer whale), Type C (Ross Sea killer whale), and Type D (Subantarctic killer whale). In the Northern Hemisphere, proposed types include resident killer whales, Bigg's (transient) killer whales, offshore killer whales, and Type 1 and 2 Eastern North Atlantic killer whales. You can see articles and images about this here and here.
Determining species of killer whales is important not only in gaining information about the whales, but in protecting them - it is difficult to determine the abundance of killer whales without even knowing how many species there are.
6. Male killer whales are larger than females.
7. Researchers can tell individual killer whales apart.
8. Different killer whale pods have different dialects.
Killer whales use a variety of sounds for communicating, socializing and finding prey. These sounds include clicks, pulsed calls and whistles. Their sounds are in the range of 0.1 kHz to about 40 kHz. Clicks are primarily used for echolocation, although they may also be used for communication. The pulsed calls of killer whales sound like squeaks and squawks and appear to be used for communication and socialization. They can produce sounds very rapidly - at a rate of up to 5,000 clicks per second. You can hear killer whale calls here on the Discovery of Sound in the Sea web site.
Different populations of killer whales make different vocalizations, and different pods within these populations may even have their own dialect. Some researchers can distinguish individual pods, and even matrilines (the line of relationship that can be traced from one mother to her offspring), just by their calls.
9. Orcas have no natural enemies.Orcas are apex predators - they are at the top of the oceanic food chain and have no natural predators. Humans have not even spent much time hunting killer whales because of their speed and streamlined bodies - according to NOAA, it would take 21 orca whales to produce the same amount of oil as one sperm whale.
10. Killer whales face many threats.
Killer whales have been caught for aquariums since the early 1960's. The first killer whale caught in the wild was in 1961. This whale died within two days after ramming into the side of her tank. According to Whale and Dolphin Conservation, there were 45 killer whales in captivity as of April 2013. Due to protection in the U.S. and restrictions on trade, most parks now obtain their killer whales from captive breeding programs. So, wild capture is not as much of an issue as it once was. While the viewing of captive orcas has likely inspired thousands of budding marine biologists and helped scientists learn more about the species, it is a controversial practice due to the potential effects on the whales' health and ability to socialize naturally.
Other threats faced by killer whales include pollution (orcas can carry chemicals such as PCBs, DDTs and flame retardants that can affect the immune and reproductive systems), ship strikes, reduction of prey due to overfishing, and loss of habitat, entanglement, ship strikes, irresponsible whale watching, and noise in the habitat, which can affect the ability to communicate and find prey.