Reasons For endangerment
Prey Availability
One of the biggest threats to the southern resident orca is prey availability. Southern resident orcas rely almost entirely on salmon for their summer diet in the Salish Sea. Specifically Chinook salmon make up 80% of the orcas diet while other salmonids including the chinook make up 98% of their entire diet (EPA, 2021). In the Salish sea, Chinook salmon populations have declined more than 60% between 1984 and 2018 (EPA, 2021). Right now, two thirds of all southern orca pregnancies fail due to nutritional stress (Endangered Species Coalition, 2020). The main reason for declining salmon populations is dam construction on the Colombia, Klamath, and Sacramento rivers. In the Columbia river basin, more than 40% of habitat availability for salmon spawning is blocked by dams (NPCC, 2022). Every year thousands of salmon swim right up to dams in hope of reaching historic spawning grounds but get cut off by hundred foot tall impassable dams built on almost every major river in the area.
Two thirds of all southern orca pregnancies fail due to nutritional
stress
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It is estimated
that more than six tons of plastic lie washed up on Salish Sea beaches at any given moment
Contaminants
A danger to the survival of the orca pods is high amounts of chemical contaminants and pollutants. Biomagnification has caused sickening mercury levels and PCBs that make their way into the orca’s stomach poisoning her and her young from the salmon they eat. The babies contain the highest levels of pollutants as they are passed down through their poor mother’s milk. The pollutants include pesticides, industrial coolants and lubricants, flame retardants, motor oil, and chemicals from other household products that enter Puget Sound and the Pacific Ocean when it rains. (U.S. Department of Commerce) The large amounts of plastic that float within the home of the Southern Resident Orca is alarming. It is estimated that more than six tons of plastic lie washed up on Salish Sea beaches at any given moment in time. These plastics are being ingested and resulting in death. With heavy amounts of pollutants within their environment these toxins not only affect the welfare of the orca but the health of an already dwindling population. The substantial amounts of pollutants being dumped into the ocean are causing reproductive system dysfunction and breaking down a fragile immune system.
Disturbance from vessels
The presence of boats and large industrial vessels greatly affects the behavior and communication of southern resident orcas. Orcas are acoustic animals who communicate through sonar. Background noise from ships can make it harder for orcas to hunt, sleep, and socialize with one another (Whale trail, 2021). In the noisiest areas, Southern Residents may lose up to 97% of their communication range (Simpson, 2019). Orcas are observed to exert much more energy when in the presence of large ships, leading to exhaustion and less energy for hunting and breeding (Wild whales, 2020). Many whales die when they become too exhausted to swim to the surface to breathe.
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In the noisiest areas, Southern Residents may lose up to 97%
of their communication range.
Just 44 Southern Orcas have been born since 1998 and within the same time frame 81 have died or disappeared.
Low birth rate
The average female lives a full 15 years at least before having her first calf. Once pregnant there is a 17 month gestation period creating a very low birth rate for the species. After birth, the mother spends lots of time with her calf, up to two to three years until finally they are ready to calf again after a five-year interval. Once a female reaches forty years of age they no longer reproduce. This means each female only gives birth to five calves. Just 44 orcas have been born since 1998, and within the same time frame, 81 have died or disappeared (Page, 2021). Each pod of Southern Resident Orcas has at least 2 post-reproductive females (Garrett, 2012).