ORCAS

Orcinus orca, commonly known as the “orca” or “killer whale”, is the largest dolphin in the cetacean family. They are the most widespread cetacean, present in every ocean across the world, and represented in varied habitats. There are several ‘subtypes’ of orca, which some scientists suggest may be separate species or subspecies. Certain populations or subtypes are considered threatened or endangered due to varying factors, such as food scarcity, human threat, and pollution; the Southern Resident population are classified as Endangered under the ESA, and the AT1 Transient Stock is classified as depleted under the MMPA. All orca populations are protected under the MMPA, although the Southern Resident is the only endangered population. There are an estimated 50,000 orca worldwide.

Taxonomically, orca are a part of Delphinidae – while Delphinidae as a group diverged from the rest of Odotoceti approximately 12-15mya, Orcinus are thought to have diverged shortly after. Phylogenetic placement of the species is under some debate, but the most recent studies suggest that Orcinus is one of the most basal Delphinidae species. There are two recognised extinct genera in Orcinus: O. citoniensis and O. paleorca. These species were both smaller than O. orca, suggesting that they slowly evolved to eat bigger and bigger prey.

Orca are the largest extant member of Delphinidae. While exact sizes can vary depending on ‘type’, on average males are 6-8 meters long and 6 tonnes, and females are 5-7 meters long and 3-4 tonnes. The largest recorded size for males is 9.8m and 10t, and for females is 8.5m. Calves are around 2.4m at birth. Males have larger dorsal fins than females – while the dorsal of the female is generally gently curved and about 91cm tall, male dorsals are tall and straight, sometimes reaching 1.8m in height. Orca reach sexual maturity between 10 and 18 years of age, and females can continue breeding until their 40s. Orca are one of the few species besides humans that go through a menopause and live past their reproductive prime – this is theorised to be because orca engage in communal care, and elder females play an important role in teaching and supporting new mothers. Females live on average between 50-80 years in the wild, with the eldest (J2 Granny) being around 80. Males live between 29-60 years in the wild, and often die along with their mothers.

Orca are easily recognised by their stark black and white pigmentation; the back and flank are mostly black, with a white underbelly that extends across the entire lower jaw, and up the flank in lateral patches. Iconically, they also have a white ‘eye patch’ – an oval patch of white situated just above and behind both eyes. There is also generally a lighter grey patch behind the dorsal fin, called a ‘saddle patch’. Both the eye patches and saddle patches are important for identification, both of ‘types’, and of individuals. Newborn orca can often appear orange or yellow tinted over their white markings, but this fades as they grow. Some types of Antarctic orca may have yellow tinting to their white markings, and this is thought to be due to diatoms in the water where they live.

A pod of orca swimming underwater

A pod of orca rubbing against pebbles

Orca are a highly intelligent and social species. They have complex social structures, with only elephants and higher primates such as chimps and gorillas having similar levels of complexity. They show strong maternal bonds, complex coordination and communication when hunting, seem to form ‘friendships’ – showing preferences in the individuals they spend time with within their social group – and even, it seems, display complex emotions like grief. Tahlequah is a female of the SRKW J pod, who has twice been observed carrying her deceased calves for days after their deaths.

Orca are often seen travelling in groups called ‘pods’. These pods are generally familial groups, surrounding a matriline – a female orca and her offspring. Males in particular are thought to never leave their mothers’ pod, straying briefly only for breeding opportunities. Within orca ‘societies’, females are generally more high-ranking despite physically being smaller, and studies suggest that females play a lot of the key social roles within pods, including discipline and teaching of juveniles. Communal care is common enough to be standard – females will hold fish in their mouths while their young chew pieces off; young females will babysit while older females hunt; and it is females, particularly the older and more experienced ones, who will pass on knowledge such as food sources, hunting strategies, and communication skills.

In Resident communities, there are four social levels: matrilines are highly stable, and almost never separate; pods may consist of 1 to 4 related matrilines, and although generally close, they may separate for weeks to months; clans are groups of pods with similar dialects and distant matrilineal connection; finally communities are groups of pods that regularly interact, but have no relation. Resident social structures are particularly stable, and due to the long lifespan of females, up to four generations can sometimes travel together. L pod is the largest pod of the SRKW community, with 34 orca all travelling and socialising together.

In Transients, pods are smaller, generally a female and a few of her offspring; on average, 3 to 7 whales travelling together regularly. However, Transients are still highly social – although in day-to-day life pods travel as small immediate-family units, they will often meet up and travel with other pods. Sometimes, these are related pods – aunts and cousins, grandmothers and grandchildren – and sometimes their matrilines are completely unrelated, and the meeting seems purely social. During these meetings, calves from the pods play together, while mothers socialise. Males still remain with their mothers for their whole lives, while females will split off as they begin to have calves of their own.

These social structures seem to correlate to diet – fish-eating populations are similar to Residents, while mammal-eaters are more like Transients. This is theorised to be due to the sharper senses of mammals, who would be more likely to notice their predators if more were travelling together. However, all orca are social, and often rely on group hunting for food. Orca have been shown to have culture-specific behaviours which can be passed across generations and between individuals, and can differ greatly between populations. It is thought that even dietary preferences – such as the diet of Chinook salmon of Southern Residents – are due to cultural traditions. Cultural fads have also been seen to come and go; in the 1980s, the West Coast orcas started to wear dead salmon across their heads. This trend faded, but seems to have become popular again in recent years. Other communities have communal ‘rubbing beaches’ that they return to, to rub off dead skin and parasites.

Another social dynamic that is different between communities is language. Orca seem to have unique languages and dialects that can vary greatly – this could mean that different populations do not understand each other. It is possible to identify what community is in an area, based on their unique base of calls; sometimes, it is even possible to identify down to the matriline, due to distinctive ‘dialects’. Lolita seemed to recognise calls from L-Pod, her natal pod, and still used those dialect sounds throughout her life. Studies even suggest that language transfer occurs ‘horizontally’ rather than solely 'vertically'. This makes it clear that orca have complex social lives. Language studies of orca, and other cognition and intelligence research, are revealing more and more new information on the rich inner lives of orca.