Killer Whale

Orcas are the largest extant members of the dolphin family. Males typically range from 6 to 8 m (20 to 26 ft) long and weigh in excess of 6 t (5.9 long tons; 6.6 short tons). Females are smaller, generally ranging from 5 to 7 m (16 to 23 ft) and weighing about 3 to 4 t (3.0 to 3.9 long tons; 3.3 to 4.4 short tons). Orcas may attain larger sizes as males have been recorded at 10 m (33 ft) and females at 8.5 m (28 ft). Large males can reach a weight of over 10 t (9.8 long tons; 11 short tons), large females can reach a weight of over 7.5 t (7.4 long tons; 8.3 short tons). Calves at birth weigh about 180 kg (400 lb) and are about 2.4 m (7 ft 10 in) long. The skeleton of the orca is typical for an oceanic dolphin, but more robust.

Orcas are found in all oceans and most seas. Due to their enormous range, numbers, and density, relative distribution is difficult to estimate, but they clearly prefer higher latitudes and coastal areas over pelagic environments. Areas which serve as major study sites for the species include the coasts of Iceland, Norway, the Valdés Peninsula of Argentina, the Crozet Islands, New Zealand and parts of the west coast of North America, from California to Alaska. Systematic surveys indicate the highest densities of orcas (>0.40 individuals per 100 km2) in the northeast Atlantic around the Norwegian coast, in the north Pacific along the Aleutian Islands, the Gulf of Alaska and in the Southern Ocean off much of the coast of Antarctica.

Orcas are apex predators, meaning that they themselves have no natural predators. They are sometimes called "wolves of the sea", because they hunt in groups like wolf packs. Orcas hunt varied prey including fish, cephalopods, mammals, seabirds, and sea turtles. Different populations or ecotypes may specialize, and some can have a dramatic impact on prey species. However, whales in tropical areas appear to have more generalized diets due to lower food productivity. Orcas spend most of their time at shallow depths, but occasionally dive several hundred metres depending on their prey. On average, an orca eats 227 kilograms (500 lb) each day.

Day-to-day orca behaviour generally consists of foraging, travelling, resting and socializing. Orcas frequently engage in surface behaviour such as breaching (jumping completely out of the water) and tail-slapping. These activities may have a variety of purposes, such as courtship, communication, dislodging parasites, or play. Spyhopping is a behaviour in which a whale holds its head above water to view its surroundings. They can also reach speeds of up to 15.5 m/s (56 km/h; 35 mph). Resident orcas swim alongside porpoises and other dolphins.

Orcas will engage in surplus killing, that is, killing that is not designed to be for food. As an example, a BBC film crew witnessed orcas in British Columbia playing with a male Steller sea lion to exhaustion, but not eating it.

Some orcas have been observed swimming with dead salmon on their heads, resembling hats.

Female orcas begin to mature at around the age of 10–13 and reach peak fertility around 20, experiencing periods of polyestrous cycling separated by non-cycling periods of three to 16 months. Females can often breed until age 40, followed by a rapid decrease in fertility. Orcas are among the few animals that undergo menopause and live for decades after they have finished breeding. The lifespans of wild females average 50 to 80 years. Some are claimed to have lived substantially longer: Granny (J2) was estimated by some researchers to have been as old as 105 years at the time of her death, though a biopsy sample indicated her age as 65 to 80 years. One of the oldest living orcas is Ocean Sun (identified as L25), a Southern Resident Orca, who is estimated to be more than 98 years old.

In 2008, the IUCN (International Union for Conservation of Nature) changed its assessment of the orca's conservation status from conservation dependent to data deficient, recognizing that one or more orca types may actually be separate, endangered species. Depletion of prey species, pollution, large-scale oil spills, and habitat disturbance caused by noise and conflicts with boats are the most significant worldwide threats. In January 2020, the first orca in England and Wales since 2001 was found dead with a large fragment of plastic in its stomach.