The Southern Resident Killer Whale

What's Killing the Killer Whales?

Emily Dekker

Image from fanpop

Description and Ecology of the Southern Resident Killer Whale

The Southern Resident killer whale, also known as Oscines orca, is actually classified as a marine dolphin, despite its name. The killer whale is the world’s largest dolphin; a male killer whale can measure a maximum of nine meters (almost 30 feet!) and weigh about 5,568 kilograms (a little over 12,000 pounds!) while a female killer whale can reach 7.7 meters (about 25 feet!) and weigh 3,810 kilograms (roughly 8,400 pounds)! The sizes and shapes of the flippers, fins, tail flukes, and girths also differ between males and females. Killer whales have black backs and white bellies and the patterns and markings show where the whale is from and can even be an indication of age. Young killer whales have yellowish markings instead of white. Each whale has unique markings and scarring that can help distinguish the whales.

Image from Whaleopedia

“Killer whales are highly social animals that occur primarily in groups or pods of up to 40-50 animals” (Recovery Plan). Most pods have two to 15 animals and are led by females. Larger populations, as well as single killer whales (often males), can also form. Killer whales communicate vocally and “like all dolphins, killer whales produce numerous types of vocalizations that are useful in navigation, communication, and foraging” (Recovery Plan).

Image from fineartamerica

If you would like more information about killer whales along with more pictures, videos, and audio, go to Whaleopedia!

Geographic and Population Changes

Killer whales live in all oceans of the world except the Arctic Ocean. They prefer to live in costal waters at higher latitudes and are classified as resident, transient, or offshore based on where they live but also on genetic differences. The Southern Resident killer whale lives off the coasts of northwest Canada (south of Alaska), Washington, Oregon, and Northern California. The Southern Resident killer whale population declined by almost 20 percent between 1996 and 2001 but as of 2007, there are 87 Southern Resident killer whales in the Southern Resident distinct populations segment.

Image from the Recovery Plan

Geographic ranges (light shading) of the Southern Resident killer whale populations in the northeastern Pacific.
Image from the Recovery Plan

Listing Date and Type of Listing

In 2001, the killer whale “was petitioned for listing under the ESA” and since then, the population increased to 87 whales in 2007. Before it was listed as endangered it was determined by the National Marine Fisheries Service that the killer whale “was below its optimum sustainable population” and was designated “as depleted under the Marine Mammal Protection Act in May 2003” (Recovery Plan). The Southern Resident killer whale “was listed as endangered under the Endangered Species Act on November 18, 2005” (Recovery Plan).

Image from National Geographic

Cause of Listing & Main Threats to its Continued Existence

The killer whale was listed as endangered because of its dwindling population, however, “it is unknown which of the threats has caused the decline or may have the most significant impact on recovery of the population” (Recovery Plan). Some of the possible threats include: prey availability, pollution and contaminants, vessels effects, sound, oil spills, disease, small population size, live-captures, etc.

Specific Threats to the Southern Resident Killer Whales
Image from the Recovery Plan

Recovery Plan

In order to recover the Southern Resident killer whale, it is important that every possible threat is eliminated or controlled. It is vital that the populations of salmon and other prey also be rebuilt as a food source for the killer whales. Another step in the right direction is minimizing pollution and chemical contamination in their habitat and minimizing disturbances from vessels such as whale-watching ferries. Reducing oil spills will also help with the recovery of killer whales along with monitoring infectious diseases. Minimizing invasive species, developing public education programs, and helping stranded, sick, or injured killer whales would also help their recovery. Finally, research and monitoring killer whales will help with recovery of the species.

Image from Wikipedia

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