There are three distinct types of orca that live in the waters off the coast of western North America. These three assemblages have distinct differences in their diet, range, behaviour and social systems.
Photo credit; Santisouk Phommachakr
Resident orcas range from SE Alaska down to the coast of Oregon, although in recent years some of the pods have been seen as far south as California in the winter months. Resident orcas are salmon specialists, and Chinook salmon makes up the majority of their diet, year-round. These whales rely on echolocation to find their prey.
Resident orcas appear to be split into two communities, which are known as “Southern” and “Northern” residents. In over 30 years of research, members of the two communities have not been found in the same area at the same time.
Bigg’s (transient) Orcas
Bigg’s orcas were formerly known as ‘transients’. In 2012, a push was made to rename this type of orca in memory of Dr. Bigg. Bigg’s orcas range all along the west coast of North America, from California to Alaska. They are mammal-eaters, specializing on smaller marine mammals such as seals, sea lions, porpoises, dolphins, and occasional calves or juveniles of larger species such as grey whales and humpback whales. In fact, the term “killer whale” is derived from this type of orca, which is the only species of whale that kills other whales.
For Bigg’s, traveling in smaller groups is important to be able to efficiently hunt and catch their prey. Unlike fish, marine mammals can hear very well underwater, so Bigg’s orcas vocalize and echolocate very rarely while searching for their prey. Instead, they follow the coastline, checking each cove for unsuspecting prey and use passive listening to locate seals and small cetaceans. Bigg’s typically vocalize either during or directly following a kill.
Very little is known about offshore orcas because they tend to spend most of their time offshore along the continental shelf. Some groups have been sighted in inshore waters and even deep into coastal inlets. Offshore orcas are typically encountered in groups of 30 – 70 whales or more. Nothing is known about their social structure.
It is thought that these orcas eat large ocean fish such as sharks and halibut. Compared to transient and resident orcas, offshore orcas have a large proportion of nicks and scarring, possibly from catching sharks. The few offshore orcas that have stranded had teeth that were significantly worn down, which would also occur from consuming sharks which have very tough skin.
Offshore orcas are acoustically distinct from resident and transient orcas, but little is known about how they use their calls and how this differs from resident and Bigg’s orca behaviour.
Orcas along the coast of British Columbia and Washington are some of the best-studied whales in the world. Intensive field research in this region has been in progress for almost 30 years. In the early 1970’s photo-identification of orcas was established by the late Michael Bigg of Fisheries and Oceans Canada. This technique was integral in allowing researchers to identify individual orcas and by extension estimate population sizes, movement patterns and provide insight into social structure and birth and death rates. Photo identification is a technique that is undertaken to this day; identification catalogues are continually being updated by Fisheries and Oceans Canada and the Center for Whale Research. However, while these studies have increased knowledge about these whales they also illustrate how much remains to be learned.
Size: to a maximum length of 9 metres (30 feet)
Colour: distinctive pattern – black on the back, white on the belly, grey “saddlepatch” behind the dorsal fin, white “eyepatch” located just behind the eye
Dorsal fin: curved towards the back, up to 1.8 metres (6 feet) in height, in the middle of the back
Blow: small and puffy
Tail fluke: black on top and white underneath, in males, the tips curve downwards
Surface behaviour: in large groups, often surface in groups or in unison, aerial behaviours are very common (e.g. breaching, spyhopping, tail-lobbing, pectoral fin slapping)
Excerpted from; https://wildwhales.org/killer-whale/
Join VG Photography Tours on our Whales and Bears photography tour, September 2 - 9, 2017 when we will spend a full day on the water searching for and photographing this majestic mammal, as well as the abundance of other wildlife to be found on the scenic west coast of Canada.