Orca Awareness Month: Southern Residents (Part One)

June is Orca Awareness Month! We wanted to focus this post on the Southern Residents because they are the most endangered population of killer whales. Yet, they are among the most studied whales in the world. We know so much about them. Here is a little introduction to these beautiful majestic whales.

killer whales
ยฉ Jared Towers

Populations and Ecotypes

Found in every ocean, killer whales (Orcinus orca), or orcas, are cosmopolitan. Typically found in the higher latitudes, they do inhabit more tropical regions like the Bahamas. Up in the Northeastern Pacific, three types of ecotypes inhabit the area, Resident, Transient, and Offshore killer whales (labeled as A, C, and D on the figure below). As a general gist with ecotypes, these classifications describe a few orca populations. It does not describe all orca populations. It is based on body size, coloration, habitat range, vocalizations, diet, and social structure. The Southern Residents Killer Whales (SRKW) are one of the most well-known populations of killer whales. They belong to theโ€œResidentโ€ ecotype.

SRKW habitat

As residents, the SRKW’s stay with natal groups or pods in the Salish Sea. Their distribution ranges between Washington State, USA, and British Columbia, more specifically around the Strait of Juan de Fuca, the Strait of Georgia, and Puget Sound. Each pod (large extended family) follows its matriarchal lineages. Both male and female killer whale offspring stay in these pods with their mothers their entire lives. Three pods (J Pod=22, K Pod=17, L Pod=34) make up the SRKWs population. One member of the SRKW actually lives at the Seaquarium in Miami, Florida. Lolita, also known as Tokitae, is about 50 years old. The total number of SRKW is 74 individuals (excluding Lolita) making this population of killer whales the most endangered on Earth.

Initially, scientists thought SRKW only inhabited the Salish sea. However, SRKWs have recently shown a continuous presence traveling as far south as Monterrey Bay, California, U.S.A. Typically, they travel there during the winter/spring months.

SRKW Vocalization

There are major similarities between the three pods’ overall body size, coloration, and diet. Scientists utilize dorsal fin shapes and saddle patches (the grey markings behind the dorsal fin) as unique identifiers for each individual killer whale. They also identify pods from their vocalizations.

Their vocalizations typically consist of clicks, whistles, or pulse calls, like other dolphins. Clicks are used for echolocation (20-30kHz to 40-60kHz) and help them find their prey. Whistles (0.5-40kHz with peak energy at 6-12kHz) are typically used for close-range or “private” communication. Pulse calls are thought to function as group recognition and coordination of behavior. They range depending on the ecotype. Vocalizations are important for hunting in these pods as they use a lot of cooperative behavior.

Below are some audio examples of J, K, and L pod vocalizations.

Recordings of J-pod vocalization from Ocean Networks Canada
Recordings of K-pod vocalization from Ocean Networks Canada
Recordings of J-pod vocalization from Ocean Networks Canada

SRKW Diet

Their diet consists of salmonids (about 90%). The SRKW are notorious for consuming Chinook salmon (Oncorhynchus tshawytscha). Experts estimate that SRKW’s consume 190,000 to 260,000 adult Chinook salmon each year. Like most salmon, they are anadromous fish. Anadromous fish can live in both fresh and saltwater. The first step in Chinook Salmon’s life history is to spawn in rivers. As the second step of their lives, they migrate to saltwater to feed, grow, and mature. Finally, to complete the circle of life, they return to freshwater to spawn and die. The SRKWs utilize a lot of cooperative behavior to wrangle their prey.

This concludes Part 1 on the SRKWs! Comeback for Part 2 where we will discuss SRKWs population declines and threats (including pollution).

For more information about the SRKWs:

Thanks for Reading!

Naomi Mathew is a PhD student at University of Louisiana at Lafayette. She works on bioacoustics in marine mammals from the Gulf of Mexico. She is the co-founder of Whale Scientists. You can read more about her here

Share this:

Leave a Reply