Polaris, Dipper and the Death of the Southern Resident Killer Whales: Part 3: Toxins


Polaris, Dipper and the Death of the Southern Resident Killer Whales: Part 3: Toxins

Guest Blogger: Courtney Halvorson

The Center for Whale Research, which is the primary research institution studying the Southern Resident Killer Whales, have been observing that the whales have been noticeably absent from their core summer habitat. They are having to look harder for scarce and significantly smaller fish, which means they have to eat more individuals for the same amount of energy. This increase in individual fish consumed poses its own threat to the whales, as these salmon have toxins worked into their fat. These environmental toxins are called PCBs or Polychlorinated Biphenyls. They are fat-binding molecules that never break down and will be in the ocean forever and have been put there by humans, particularly in flame retardants. As fatty marine mammals, whales of all sorts have a thick layer of blubber to keep warm. So as the whales accumulate more fish, these toxins are then worked into blubber and stored within the body. The blubber of the Southern Resident Killer Whales is full of these PCBs. When food is scarce these toxins are re-suspended in the body because the fat is metabolized for energy.

Pregnant and lactating females are the most at risk to toxicity as these biological functions require significant energy – which these females are not receiving from their diet and are now getting from their blubber. Mothers, like Polaris, grow a calf for 17 months and then then nurse it with high fat milk ridden with toxins. Whale milk can be up to 50% fat, which keeps it together in a thick consistency so it can move through the water without breaking up. Fat binding PCBs have been shown to cause problems with reproduction, immunity and proper nervous system function.

We are not only losing current individuals in the Southern Residents killer whale population, but we are risking the next generation. Approximately 65% of pregnancies have been ending with miscarriages – and many of these are occurring in the late stages of pregnancy. This is the most dangerous time for the mother to abort.

It was only December of 2014 when a young J-pod mother-to-be Rhapsody (J-32) was found deceased near Comox on Vancouver Island with a late-term fetus still inside her uterus. At only 18 years old, Rhapsody was just beginning her reproductive life. Rhapsody was also showing signs of starvation.

Sam Wasser and his team at the Center for Conservation Biology located at the University of Washington have developed a method of extracting hormones from whale faeces which is a non-invasive way of closely monitoring the whales’ health.  This team is complete with a dog named Tucker who is trained to sniff out the faeces from a boat. Hormone levels can help researchers determine the different stages of pregnancy, level of stress from external sources, any nutritional deficiencies and rate of metabolism. This has allowed researchers to link food availability with the success of a pregnancy.

Check out parts one and two and stay tuned for part four tomorrow! 

Courtney Halvorson is a PNW educated Marine Biologist, Wildlife Photographer and Marine Naturalist for Orca Spirit Adventures in Victoria, British Columbia.

Photo Credit: Susanne Davies