Welcome back Orca-lovers to our third blog, which will be split into 2 parts. This time we’re exploring the different ecotypes of killer whales in the Northern Hemisphere. So, the following blog will be about the orcas in the Southern Hemisphere.
So, the first question is of course: What is an Ecotype?
These distinct types of orcas differ in size, appearance, prey preferences, foraging techniques, dialects, behaviours, and social groups. Their ranges often overlap, but they are also genetically distinct – they don’t appear to interbreed and rarely interact with other ecotypes.
We differentiate them into orcas from the Northern Hemisphere and the Southern Hemisphere. As we are in the northern hemisphere, in Iceland, we will start with these ecotypes!
North Atlantic: Type 1
These orcas are smaller than other orcas and generalist eaters. Males can grow up to 6.7m. They prey mostly on herring and mackerel around Iceland, Norway and Scotland, but some have been seen feeding on seals as well. Their teeth are worn down up to the gum, because of the fish scales. Like other orca ecotypes, the different communities have different prey preferences and different home ranges. Type 1 killer whales mostly use the carousel feeding technique to hunt and live in tightly connected pod communities.
Very excitingly, within the last week we have had two sightings of these type 1 orcas within Faxaflói Bay!
North Atlantic: Type 2
Type 2 orcas prey primarily on other cetaceans, especially on minke whales. These rarely seen orcas are large, with distinctive back-sloping eye patches and can grow up to 8.5m. To consume marine mammals, they have bigger and sharper teeth to rip off the flesh. However, as with other mammal-eating orcas, they are threatened by chemical pollutants such as PolyChlorinated Biphenyls (PCBs). Although they’re also found in Norway and Iceland they’ve also been seen as far south as the Azores. Unfortunately, there is not a lot of data about this ecotype, since there are only samples of 5 individuals.
North Pacific: Resident Orcas
Resident orcas are named so because they have small home ranges around areas of large fish populations. Their prey doesn’t migrate which allows them to remain in certain areas without facing a lack of food. They are the best studied ecotype of all orcas and can grow up to 7.2m. Residents are found on both sides of the North Pacific. The Northern and Southern communities almost exclusively eat salmon, while Residents in Alaska appear not to be picky in their fish preference, eating multiple fish species including salmon, mackerel, halibut and cod. Research has shown that fish-eating orcas off the coasts of Russia and Japan prefer salmon and mackerel.
Resident orcas live in family groups within larger communities, divided by matrilines and pods. Offspring live with their mother for their entire lives. These communities are genetically and acoustically distinct from each other, and each has unique traits specific to their group, like the beach-rubbing behaviour of the Northern Residents for example.
So, the Residents can be split into at least three distinct communities: the northern, southern and southern Alaskan Residents. The latter can be found from south-eastern Alaska to the Kodiak Archipelago and has over 700 individuals. They consist of two interbreeding clans distinguished by acoustic calls and whose ranges overlap. The northern Residents live in coastal and inland waters from south-eastern Alaska to Vancouver Island and consist of three clans,16 pods with over 300 individuals. The southern Resident Orcas on the other hand only consist of one clan and three pods with a population estimated to be 73 individuals and are listed as endangered. This is due to vessel traffic noise and disturbance, contaminants in the food source and prey availability. They inhabit the inland waters of southern British Columbia and Washington but can also be found in the outer waters off Vancouver Island, Washington, Oregon and California.
North Pacific: Transient/ Bigg’s Orcas
The Transients are also called Bigg’s killer whales, because of the Canadian scientist Michael Bigg who was the first to describe differences between the Residents and Transients. He noted in the 1970s that the two animals did not mix with each other even when they occupied many of the same coastal waters.
They feed upon marine mammals such as minke whales, gray whale calves and seals. All marine mammal eating orcas are of larger size and the Transients are no exception, they grow up to 8m! Bigg’s travel frequently over large ranges, from Baja California in Mexico up to the Arctic Circle. They’re also very family-orientated like other orcas but they live in smaller groups. This is because they prey on mammals which are harder to come by than fish stocks. Some of the offspring stay with their mothers for life, some of them leave. Bigg’s vocalise in less variable and less complex dialects.
This population also suffers from chemical contamination through their food source, these contaminants get stored in their blubber. This can lead to infertility, immunosuppression or even neurological problems. Females also rely on their blubber to produce milk for calves, so it is passed between generations. The calves will hold these contaminants in concentrations 18x higher than the mother. This will be discussed more in a future blog, where the threats orcas face are looked at.
There are at least three different "stocks" of Bigg’s off North America. The first stock can be found from Prince William Sound to Kenai Fjords. The second stock in the Gulf of Alaska, Aleutian Island and Bering Sea. Finally, the third is the west coast stock, which ranges from southeast Alaska to California. The first stock is considered a depleted stock; it was affected by the Exxon Valdez oil spill and declined from 22 individuals to eight between 1989 and 2004. The second stock numbers around 500 individuals while the third stock has over 320 orcas with over 200 along southeast Alaska, British Columbia and Washington and over 100 orcas off California.
Offshore Orcas
They are found in the North Pacific, but little is known about the elusive and smaller Offshore orcas, which only grow to around 6.7m. As they live far from land, mainly over the outer continental shelf, they are rarely encountered. Their large range stretches from Southern California to the Bering Sea, up to Russia. Their social structure and prey preferences are still unknown. But they have been seen in large groups with more than 50 individuals, with occasional sightings of larger groups of up to 200, and preying on both fish and sharks. The teeth of Offshore orcas are often worn down, indicating that they’re eating things with rough skin (like sharks). They have been seen sharing food with older individuals who likely cannot make kills due to damaged teeth from a life of shark hunting. They are the smallest of the three North Pacific ecotypes and are more closely related to Residents than to Bigg’s orcas, though all three ecotypes are genetically distinct.
This was part 1 of the Ecotypes, but don´t be sad, Part 2 will be coming soon where the ecotypes of the southern hemisphere will be examined, so stay tuned for more!
Kylie Veal
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