A very charismatic species of dolphin with a contrasting and attracting coloration, there is no doubt everyone loves orcas! 😀
orcas are often called killer whales, a name given by sailors who observed them hunting and feeding on whales. They have a wide distribution ranging from the equator to the polar regions, and are mostly found in nearshore and in high-productivity areas.
So far they are considered a single species, divided into ten different ecotypes differing for genetics, morphology, behaviour and diet. We cannot exclude that in future the species will include subspecies or even will split into different species.
Here is a list of the ecotypes:
Resident – They are found in both sides of the North Pacific. They live in family groups within larger communities and their offspring live with their mother for their entire lives. They feed exclusively on fish (mostly salmon)
Transients or Bigg’s – They are the second ecotype of the North Pacific. They live in small groups and travel frequently over large home ranges. They feed on marine mammals (harbor seals, minke whales, gray whale calves) and due to their diet they carry high toxin loads. They are less acoustic than residents
Offshore – They are the third ecotype found in the North Pacific. They live in large groups far from the shore and little is known about their social structure and diet. They have been seen preying on both fish and sharks and for this reason their teeth are often worn down.
Type 1 – They are found in the North Atlantic. They are small and appear to be generalist in their diet. They eat herring and mackerel around Norway, Iceland, and Scotland, but some have been seen feeding on seals as well.
Type 2 – Also found in the North Atlantic, they are larger and prey primarily on other whales and dolphins, particularly minke whales, for this reason they also carry high toxin loads.
Type A – Large orcas found in Antarctic waters, where they primarily hunt minke whales, following their migrations.
Large Type B or Pack ice – They are found around the Antarctic continent and forage for seals in the loose pack ice. They are famous for hunting in cooperation using their tails and bodies to create waves to wash seals off ice floes.
Small Type B – Their preferred diet is unknown, but they have been seen feeding on penguins and are usually spotted around penguin colonies.
Type C – They are found in the Ross Sea and is the smallest ecotype with males reaching 6m. They have been seen eating Antarctic toothfish, but it is not known if they feed exclusively on fish.
Type D – They are the most distinctive among orcas for their shorter dorsal fins, rounder heads, and smallest eye patches. They feed on Patagonian toothfish, but it is not known if they feed exclusively on fish.
Other populations of orcas could be also new ecotypes, but we don’t have enough information, for example the ones in the Strait of Gibraltar which feed on tuna, may be a third North Atlantic ecotype.
And in the Azores? orcas are sighted here only occasionally, and not every year. Usually they stay around for one or two days making it difficult to identify the ecotype or any other characteristics.
Your thoughts on this?