Orca Facts

Orcas are large, powerfully built toothed whales with marked sexual dimorphism: adult males reach up to 32 feet and about 12,000 pounds, females 23 to 26 feet and up to 8,000. Streamlined and driven by a large horizontal tail fluke, an orca can burst to about 34 mph after prey. The clearest sex difference is the dorsal fin — over 6 feet tall and near-triangular in adult males, shorter and more curved in females. Like all dolphins it uses echolocation: forcing air through nasal "phonic lips" to make high-frequency clicks that a fatty forehead organ (the melon) focuses into a beam, reading the returning echoes to build a detailed acoustic picture and hunt in darkness or murky water. Its jaws carry up to 56 large, interlocking conical teeth for grasping and tearing. It is the only species in its genus, having split from other oceanic dolphins 5 to 10 million years ago; distinct "ecotypes" — Residents, Bigg's/Transients, Offshores, and more — differ so much in diet, form, and behavior that many biologists argue they should be separate species.

The orca is the most widely distributed mammal on Earth after humans, with a truly cosmopolitan range across every ocean basin and most seas — Arctic, Atlantic, Indian, Pacific, and Southern. Though found in open pelagic and warm tropical water, orcas concentrate in productive cold-water upwelling zones at high latitudes, off the Pacific Northwest, Norway, Iceland, Antarctica, and New Zealand. Their distribution is set less by temperature or depth than by the dietary specialization of the local ecotype.

As apex carnivores with no natural predators, orcas prey on more than 140 species across their range, but each population tends to be a strict specialist. North Pacific "Resident" orcas are obligate fish-eaters focused almost entirely on specific salmon (mainly Chinook), leaving marine mammals alone, while "Bigg's" (Transient) orcas in the same waters hunt seals, sea lions, porpoises, and even large baleen whales, and some Antarctic ecotypes specialize on penguins or minke whales. Hunting is cooperative: taking schooling fish, pods use "carousel feeding," herding fish into a tight bait ball with bubbles and flashing white undersides before stunning them with tail slaps; Antarctic orcas use "wave-washing," charging an ice floe together to wash resting seals off it toward the pod.

Orca society is among the most stable known in any non-human animal — matrilineal, centered on an old, experienced matriarch, a pod typically being the matriarch, her sons and daughters, and her daughters' offspring; in some ecotypes offspring never permanently leave their mother's pod. Related pods sharing a maternal ancestor form a "clan," and clans with a similar acoustic repertoire form a "community." Acoustic communication is the bedrock: each pod has a distinct, culturally transmitted dialect of whistles, pulsed calls, and squawks — a vocal family badge that lets members recognize each other over distance and helps ensure they mate outside the pod. Passing hunting techniques, routes, and dialects across generations is true animal culture.

Orca reproduction is high-investment with long social learning. After one of the longest gestations of any mammal — about 17 months — a female bears a single calf, usually tail-first, that is mobile soon after birth and nurses on lipid-rich milk for up to two years, with older siblings and "aunts" helping guard it. Females mature around 15, and orcas are one of the few animals (with short-finned pilot whales and belugas) known to go through menopause: females usually stop reproducing around 40 but live into their 80s or 90s, and these post-reproductive matriarchs are ecologically crucial, leading pods to traditional foraging grounds in lean years and sharing their catch. Males live shorter lives, roughly 30 to 50 years.

The IUCN lists the orca globally as Data Deficient, because of the unresolved question of whether it is really several species, but many specific populations are deeply imperiled and listed as Endangered. The Southern Resident killer whales of the Pacific Northwest are critically endangered, facing an existential threat from the collapse of their obligate prey, Chinook salmon, through dams and overfishing. As apex predators orcas also bioaccumulate persistent pollutants like PCBs and heavy metals that collect in their blubber and impair immune and reproductive function — and contaminated females pass them to calves in milk — while underwater noise from shipping, sonar, and seismic testing disrupts echolocation, hunting, and communication. Long-term measures include ecosystem-based management, cutting marine pollution, and rebuilding depleted prey.

• IUCN Red List of Threatened Species: Orcinus orca
• National Oceanic and Atmospheric Administration (NOAA): Killer Whale
• Whale and Dolphin Conservation (WDC): Orca
• World Wildlife Fund (WWF): Orca