It's National Marine Week and Summerwatch young guest blogger, Chris Daykin has sent us a blog on the Orcas of the west coast of Scotland.
The killer whale, otherwise known as the orca, is one of the world’s most widespread predators and is found in all the oceans from the Antarctic to the Arctic. It is a predator at the top of the food chain, hunting even great white sharks. The west coast of Scotland is host to a community of 9 orca, made up of 5 females and 4 males. The five females consist of Nicola, Lulu, Moneypenny, Puffin and Occasus. BBC Wildlife named Occasus as part of a competition run in 2011. The four males in the community are John Coe, Floppy Fin (unusually for a wild orca, he has a collapsed dorsal fin, hence the name), Aquarius, and Comet. John Coe is easily identified due to the large nick in his dorsal fin. It is easy to distinguish the males and the females as the males have much larger dorsal fins and can be at least one metre longer than the females.
Photo by Pat Boreham
It is not known how these orca are related, however some of these females may be mothers to the males. Most orca communities display a matriarchal structure where the large bull orcas stay with their mothers. Breeding will occur when two different pods meet, allowing unrelated males and females to mate. While many populations of orca are known for their charismatic surface behaviours such as spyhopping and breaching, the west coast community appear to be quite reserved when it comes to this. Using observations in the field, and analysis of their teeth, it is thought that this population will hunt and eat only other cetaceans such as harbour porpoises and minke whales. Orcas can travel huge distances, and John Coe has been seen with other orcas from this community off the coast of both Wales and western Ireland. However, last year was a first: a sighting of John Coe and two other orcas from the West Coast community was confirmed off the coast of Peterhead, on the eastern side of Scotland.
Photo by Hebridean Whale Cruises
This population is critically endangered, as a calf has not been spotted with the group for several years. The females in the community are thought to be post-reproductive. Orcas are one of the few species that will go through menopause. The reason for this is that it allows the mother to care more for her offspring, allowing longer survival (which average 30 years for females and 19 years for males).
Genetic analysis has shown that this population of orcas may be more closely related to Antarctic orca than north Atlantic orca. This means that the West Coast community and north Atlantic orca have several physical differences. For example, the west coast community are larger on average by one metre. Unlike other populations of orcas across the world, their eye patches slant downwards towards the rear. This year the Hebridean Whale and Dolphin Trust launched a survey using techniques such as acoustic monitoring and photo identification, which will allow them to learn more about this community.