The Endangerment of Ocean's Top Predator: The Killer Whale

by Lexie Clarke

Everyone, take a second and remember the first time you ever laid eyes on a killer whale. Was it a whale-watching escapade? Watching Free Willy as a kid? Whatever it was, your first thought probably went something like, “Whoa…that is probably the coolest thing I’ve ever seen.” But, did you ever think that one day they might be gone? Probably not.

Hakan Karlsson/Getty Images/Vetta

Description and Ecology of Organism

Among other kinds of killer whales, the Southern Resident is a member of the family Delphinidae, and is the top predator of the ocean. The killer whale is the world’s largest dolphin, with the average male measuring 30 feet long and weighing about 12,000 pounds, and females reaching about 25 feet long, and about 8,400 pounds (Recovery Plan). These whales have an average life expectancy of 29 years for females and 17 years for males. They are voracious travelers, capable of traveling an average of 75 miles every day, sustaining a speed of about 8 miles per hour for long periods, and as fast as 30 miles per hour for short periods (Center for Whale Research). These animals use echolocation during foraging, and feed primarily on salmonids (National Marine Fisheries Service). These whales exhibit advanced vocal communication, and live in established social groupings (containing 40-50 whales per pod), and are dominated by a chosen female, or “matriarch.” Much is unknown about the killer whales mating behavior, but it is known that they are polygamous animals that primarily mate from April to October, and nearly always mate outside of their pods in order to reduce inbreeding (Barrett-Lennard and Ellis 2001).

Male, Female, and Newborn
Courtesy of the Cetacean Society

Geographic and Population Changes

Killer whales are classified into resident, transient, or offshore based on their geographic distribution. As a part of the resident category, the Southern Resident inhabits the inland waters of Washington State, Oregon, and southern British Columbia almost year round. During the winter, there have been sightings off the west coast of Vancouver Island and as far south as Monterey, California (Center for Whale Research). Among the three resident populations of killer whales, The Southern Resident Killer Whale is the most threatened, experiencing a 20.4% population decline between 1995 and 2001, leaving a mere 77 left (estimated historical level was about 200 during the late 1800s) (Recovery Plan). However, as of 2007, there are 87 Southern Resident Killer whales, proving some effectiveness of the Recovery Plan.

Vancouver Aquarium Cetacean Research Program

Listing Date and Type of Listing

The Southern Resident Killer Whale was listed as endangered on November 18, 2005, after being petitioned for listing under the ESA in 2001 (Recovery Plan). Prior to this, the National Marine Fisheries Service had deemed the killer whale populations “below optimum sustainable population,” and “depleted under the Marine Mammal Protection Act in May 2003” (Recovery Plan). Despite the minor increase in population since the implementation of the recovery plan, the Southern Resident is still listed as endangered.

Population Size and Trend of Southern Killer Whales
Recovery Plan

Cause of Listing & Main Threats to Continued Existence

There are inherent risks always present in small populations, making it hard to identify the biggest cause of decline. Based on over 30 years of research, the recovery plan was targeted towards the three main causes of decline: prey availability (thought to be the biggest cause), vessel interactions, and exposure to high levels of toxicants (Center for Conservation Biology). The Killer Whale’s primary food source, the Chinook salmon, is in extremely high demand from commercial fisherman, who for long periods considered the whales “fish stealers.” Killer whales consume about 3.6-4 percent of their body weight daily (Sergeant 1969, Kastelein et al. 2000), and with the overexploitation of their main food source, it is nearly impossible for them to find this amount of food. Researchers also list sound, disease, oil spills, and live – captures as primary threats.

Primary threats to Killer Whale Populations
 Recovery Plan

Description of Recovery Plan

The Recovery plan is focused on several factors to eliminate threats and improve population numbers. The first one addressed is to monitor the populations of salmon and other prey, attempting to rebuild their primary source of food. Next, the plan is focused on minimizing exposure to toxins and pollution, as well as reducing both chemical contamination (in their habitats) and sound pollution (vessel disturbances. Maintaining protection from oil spills while improving oil spill response techniques will also help with the recovery of these animals. Lastly, the plan aims to monitor infectious diseases, helping sick, injured, or stranded whales, as well as furthering their research and educating the public on how to save these magnificent animals.

Want to learn more?

Visit these links for further info and some cool videos!

http://www.nmfs.noaa.gov/pr/species/mammals/whales/killer-whale.html

http://www.whaleresearch.com/#!orca-population/cto2

http://www.livescience.com/27431-orcas-killer-whales.html

https://www.youtube.com/watch?v=-7E7FTSsbkg

https://www.youtube.com/watch?v=zJVxP7gZ4HQ