The Southern Resident Killer Whales (SRKW) represent the smallest of four resident communities within the eastern North Pacific Ocean. It is the only Killer Whale population listed as endangered by the U.S. Fish & Wildlife Service. It is currently protected under the Endangered Species Act as of 2005.[1] They are commonly referred to as the "Orcas of the Salish Sea",[2] "fish-eating orcas", or the "SRKW" population. Unlike other resident communities, the SRKW is only one clan (J) that consists of 3 pods (J, K, L) with several matrilines within each pod.[3] There are approximately 89 individuals that make up this small population. In December of 2011, a new baby orca was added to the Jclan. [4][5]
Contents |
Photo identification over the last 30 years has allowed researchers to track the southern resident population quite accurately, such as the Orca ID site[6] offered through the Center for Whale Research. Their population is built upon a matrilineal system where these strong hierarchical groups of individuals are connected by maternal descent. Each matriline consists of a female, her sons and daughters and the offspring of her daughters; averaging anywhere from one to seventeen individuals and one to five generations within each of these matrilines.[3] Pods are groups of matrilines that share a maternal ancestor, in which the southern residents consist of three pods. The number of individuals changes due to birth and deaths.
The Orca Network provides a list (last updated November 12, 2009). The following is the basic social structure:[5]
Similar dialects amongst pods create the social grouping called "clans". It is believed that the more similar their dialect is within the pods, the more closely related they are. The southern dialect is very different from other communities. For instance, northern residents use whistles as their main type of close-range communication and the southern residents use whistles for regular social interactions and long-range communications. Southern residents appear to be much more vocal but it could be due to their vocal usage during travel and the fact that they seem to travel more than the northern residents.[3]
The southern residents have reportedly been seen off the coast of Oregon, Washington, and Vancouver Island. Recently, they've been spotted as far south as the coast of central California and as far north as the coast of Queen Charlotte Islands. During the Spring, Summer, and Fall, the southern residents tend to travel around the inland waterways of Puget Sound, Strait of Juan de Fuca, and southern Georgia Strait.[7] Little is known about their range and movements within the winter months.
Southern residents are fish-eating orcas that appear to prefer the Chinook salmon to other fish species. From visual sources, necropsy, and feces collection, the following food preferences have been reported:[3]
The major threats to this very small community have been listed as:[3]