Over the last few decades, the number of calves born in the Southern Resident killer whale population has been falling, as they struggle to find enough salmon to eat. Due to malnutrition, 69% of Southern Resident killer whale pregnancies are miscarried, or die at, or shortly after their birth. Most females are only able to raise a healthy calf every 10 years, and some have had no surviving calves at all.

By comparison, Bigg’s killer whales (aka transients) have access to a plentiful food supply of marine mammals, and these females are mostly producing a calf every three to five years. This demonstrates the stark difference between these two populations, both feeding in the Salish Sea, but who have access to different food sources.

Most killer whale females reach sexual maturity in their early teenage years, while males don’t begin breeding until they’re around 25. One of the most fascinating aspects of killer whale biology is that females, like humans, go into menopause in their early 40s. This has only been documented in four other species of cetaceans and no other mammals. This means that a Southern Resident female may only produce five calves during her reproductive lifetime. This abnormally low reproduction rate keeps this population on the endangered species list.

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