Orcas: the ocean dolphins with families, dialects and cultures
Killer whales are the largest dolphins on Earth. They live in tight family groups, speak in pod-specific dialects and have regional hunting traditions.
Orcas are among the most recognisable animals on the planet, with their sharp black-and-white markings and tall dorsal fins. Several of the most popular images in our Ocean & Coast collection show them breaching or travelling in groups. Behind the striking looks is one of the most socially complex animals in the sea.
Not actually whales
Despite the name “killer whale”, the orca (Orcinus orca) is the largest member of the oceanic dolphin family. Adult males can grow to more than 8 metres long, and their dorsal fin can stand up to about 1.8 metres tall, much larger than the curved fin of females. The common name is thought to come from early sailors who saw them hunting large whales and called them “whale killers”.
Found in every ocean
Orcas live in all the world's oceans, from the tropics to the polar seas, but they are most numerous in cold, productive waters such as the North Pacific, the North Atlantic and the Southern Ocean around Antarctica.
Different populations, different diets
One of the most fascinating discoveries about orcas is that populations living in the same waters can behave almost like different species. In the northeastern Pacific, researchers recognise several distinct types:
- Residents, which eat fish, especially salmon, and live in large, stable family groups.
- Bigg's orcas (also called transients), which hunt marine mammals such as seals, sea lions and porpoises, often quietly and in smaller groups.
- Offshore orcas, which travel far from the coast and are thought to feed largely on fish, including sharks.
These groups rarely mix or interbreed, despite sharing the same coastline. Around Antarctica, scientists describe several further types with different sizes, markings and prey, some specialising in hunting seals on ice floes by creating waves to wash them into the water.
Family first
Many orca societies are built around mothers. Sons and daughters often stay with their mother's group for life, travelling, hunting and resting together. Older females, which can live for many decades, appear to lead their families to food, especially in hard years. Orcas are one of very few species, along with humans and some other whales, in which females live long past their reproductive years.
Dialects and culture
Orcas communicate with clicks, whistles and pulsed calls. Each family group has its own set of calls, a dialect passed from one generation to the next. Hunting techniques, preferred foods and travel routes are also learned socially, which is why many researchers describe orcas as having cultures.
Under pressure
Some orca populations are thriving, while others are in trouble. The Southern Resident orcas of the Pacific Northwest, for example, are listed as endangered. They face declining salmon stocks, pollution and noise from boat traffic, which interferes with the echolocation they use to find food.
See our orca wallpapers in the Ocean & Coast collection. Each one names the photographer and links to the original record of the sighting.
