Killer Whales (Orcinus orca)

Intelligent and playful, the killer whale is actually the largest dolphin. Originally named "whale killers" by Spanish sailors because of their efficient pack hunting of whales, killer whales eventually received their new fearsome moniker because of a transposition of the Spanish words. They are one of the largest predators of warm-blooded animals in the world, yet have overcome this reputation to take their place in the public's heart.

Male killer whales (bulls) can be 30 feet long and weigh up to 12,000 pounds, while females (cows) measure up to 26 feet and weigh as much as 8,400 pounds. Bulls can have a straight, rigid dorsal fin of up to 6 feet tall, while cows may have a more curved, sickle-shaped (falcate) fin of up to 6 feet. Many killer whales have distinctly bent or scarred dorsal fins which help to identify them.

The striking juxtaposition of black and white on the body camouflages the killer whale in the open ocean; they are a dark, inky black on their dorsal surface and a startling white on their ventral surface.  They also have disruptive coloration, meaning the color pattern doesn’t reflect the actual shape of the body.  The white “eyespots” above and behind the actual eyes of the killer whale may serve as a decoy to distract from the real sensitive eye area in case of attack. Killer whales have large, round, paddle shaped pectoral fins, which still retain the vestigial skeletal forelimbs that remind us that these creatures of the ocean descended from land mammals.

Killer whales have acute vision both in and out of the water, yet rely mostly on distinct sounds– or sonar –  to sense the world around them. They produce distinct sounds, including trills, grunts, whistles, and squeaks. Using these sounds, killer whales can to “see” underwater, relying on the feedback from the noise to produce a 3-D audio map of the world around them. They also use these sounds for communicating, and are so specialized and distinct that scientists can identify pods solely by the sounds they make.

One of the most interesting aspects of the killer whale is its social connections. They tend to congregate in maternal groups, with a mother and her offspring, in a pod of animals. There are three kinds of pods: resident pods – stable groups of related animals who stay within an area and tend to hunt fish; transient pods – transitory groups of unrelated animals who constantly move and hunt bigger fare, such as mammals;  and offshore pods – groups of animals of which very little is known. Resident and transient groups don’t interact, and appear to avoid each other all together. Resident pods will form parallel lines with other resident pods before coming together to travel as a clan. This face-off may be accompanied by shows of dominance, including butting heads, slapping tails against the water, biting and even raking (raking the teeth against the offending killer whale).

Killer whales have a number of crowd-pleasing behaviors, including spy-hopping, (sticking the head out of the water and turning around to get a good view of the world above the water), breaching (jumping out of the water and landing with a big splash), lob-tailing, pectoral-slapping and dorsal fin slapping, all of which include slapping a part of the body onto the surface of the water.

Killer whales eat a vast variety of food.  Resident pods tend to specialize in a particular animal, often concentrating on herring or other fish, while transient pods follow marine mammals, including seals and large baleen whales. Incredibly cunning and crafty, killer whales are often compared to wolves, as they communicate efficiently, hunt in packs and are deadly hunters. Two killer whales may toss sea lions, still half-alive, back and forth before butting the sea lion to kill it, stun fish by slapping down onto the them with their tail flukes, and even slide out of the water onto the shore to scare seals into the water where the rest of the pod waits patiently for their meal. A whole pod may chase a gray whale and her calf, taking turns harassing the giant animals for hours in order to separate the calf and drown it, devouring its tongue.

In November of last year, the United States listed the Southern Resident killer whales which inhabit Puget Sound as an endangered species under the Endangered Species Act (ESA). The three pods that call Puget Sound home are declining. In addition to heavy ship noise (which changes killer whales’ calls) and whale watching (which may change their behavior), there are high concentrations of chemicals found in killer whales. The killer whale also has the dubious title of most polluted animal in the Arctic Circle due to the build up of industrial pollutants. PCBs and DDT enter the bottom of the food chain through industrial runoff, and can quickly build up in larger predators. The pollutants become especially concentrated in apex predators, and have reached record high levels in some populations of killer whales. The effects of these pollutants aren’t fully known, but could cause reproductive problems and compromised immune systems.

Read more about the killer whale attack on the white shark near the Farallon islands.

Read more about the endangered killer whale population.

http://www.noaanews.noaa.gov/stories2005/s2533.htm

http://www.acsonline.org/aboutus/policy/killerwhale.html

 

Read more about killer whales' dubious new title of most polluted artic animal:

http://news.nationalgeographic.com/news/2005/12/1213_051213_killer_whales.html

http://www.panda.org/news_facts/newsroom/index.cfm?uNewsID=53520