Jun23

Species Spotlight: Orca

Categories // Whale & Dolphin General News

Species Spotlight: Orca
Photo credit: Linda Martin (stock image)

The orca is one of the most familiar and well-known cetaceans.

Despite its original name ‘killer whale’ it is actually the largest member of the dolphin family growing to a maximum of 9.8 metres in length. They are unmistakable with their black body, a white patch behind the eye, a white chin and underbelly and a white/grey saddle behind the dorsal fin. The intensity of the black and white across the body varies between populations. Males are particularly recognisable with their tall, straight dorsal fin, which can reach almost two metres in height. Females have a shorter, curved dorsal fin.

Orcas are very sociable and inquisitive creatures, travelling in groups of 2-30 individuals. They are fast and active, typically travelling at speeds of 5-10km per hour but can travel up to speeds of 45km per hour when chasing prey. They are often seen demonstrating breaching, tail-slapping and spy-hopping behaviours. Orcas have a relatively small, bushy blow, which is only visible at close range. Despite the nickname killer whale, they have never been known to show aggression to humans in the wild and rarely amongst themselves. The name originates from the nickname ‘whale killer’ given to them by fishermen after observing orcas hunting larger species of whales.

Orcas have a cosmopolitan distribution, from tropical to polar waters and from surf zone to open sea but they are most commonly seen in cool, high latitude waters. It is believed that there are two distinct forms of orca; transients and residents. Transients typically form small pods of 1-2 individuals and roam over a large area feeding predominantly on mammals. Residents tend to form larger pods of 5-25 animals and have smaller home ranges, feeding mainly on fish.

In and around the UK we have one resident population of orcas; the West Coast Community, who have been studied and monitored since 1992. This pod was originally thought to be made up of 10 individuals, however there have been no sightings of one female (Moon) since 2001 and in 2016 another female, Lulu, was found dead on the Isles of Tiree, tangled in rope. This unique pod is now believed to be made up of eight individuals (four males and four females) which have been most regularly seen within the Hebrides and the West coast of mainland Scotland however, their range includes waters around the whole of Ireland, the west coast of Wales, the Moray Firth and Aberdeen. It is thought this pod has never been seen outside of UK and Irish waters and there has never been records of a member interacting with other killer whales. They can be distinguished from other orcas seen in and around Scotland due to their much larger size (lengths of around 8.5 metres) and the posterior sloping eyepatch, which the pod all share. The West Coast Community are specialist feeders of other marine mammals, for example minke whales, dolphins, porpoises and seals, which has an effect on their large size. This sadly also makes them more vulnerable to pollutants such as polychlorinated biphenyls (PCBs) which are known to have an impact on fertility and the immune system and is likely to be why the population has not bred for over 25 years and are very isolated and critically endangered.

The most well-known and recognised individual of the pod is John Coe who was first identified and recorded in 1980. He can be identified by a large notch near the base of his dorsal fin and chunks out of his tail fluke. In recent months there have been some rare sightings in the English Channel of John Coe and Aquarius, another male from the pod who is often seen travelling with John Coe and is identified by his dorsal fin tilting to the left. In early May 2021, a sighting of the pair from the Minack Theatre in Porthcurno, West Cornwall was the first confirmed sighting of them in English waters and the most southerly point that members of the West Coast community are known to have visited.  The pair returned and were seen once again around the Hebrides in May, but then on Sunday 13th June they were spotted by numerous members of channel relay swim teams off Dover in the English Channel. This is the furthest south-east point that John Coe is known to have visited so makes the sighting extremely important. These sightings in the English Channel are rare and show there is still a lot to learn about the movements of the West Coast Community. Although it is believed there are eight members of the pod, since 2016 only John Coe and Aquarius have been recorded.

As well as the West Coast Community, other groups of orca are regularly seen in UK waters; North Atlantic type 1 populations of orca visit Scottish waters, they are on average 6.6 metres in length (smaller than the West Coast Community) and feed on fish, such as herring and mackerel, as well as smaller mammals, such as seals and porpoises. There is also a pod, the 27's who are a northern community and are believed to be resident as they have been recorded every month throughout the year since 2017, mainly from Shetland. The 64s and 65s pods are also now believed to be residents or semi residents as they are regularly seen in our waters. 

Orcas face numerous threats many of which are caused by humans. They were once captured in large numbers for aquariums and sea parks, and although there are still a number of individuals in captivity throughout the world this number has significantly declined in the last two decades. In the wild orcas are at risk from pollution and the depletion of their prey. They also suffer from accumulation of contaminants in their bodies. Marine animals cannot process contaminants; this means that the concentration of contaminants steadily increases as you move up the food chain. As a predator at the top of the food chain, orcas are especially vulnerable to pollution from toxic chemicals as it accumulates up the food chain (bioaccumulation). The toxins are stored in their blubber layer and travel around their body causing reduced immune function, damaging reproductive organs and leading to cancer. Female orcas will even offload the toxins to their new born through the rich fatty milk she produces using her fat stores. The West Coast Community are particularly threatened by this and in 2016 the death of a female from the pod, known as Lulu, showed the highest level of toxins ever recorded in an animal.