2 Southern Resident killer whales swimming together.
Photo courtesy of Jeff Hogan.

Each spring, the Southern Resident killer whales share their Salish Sea foraging grounds with one of the unlikeliest of their distant cousins, the gray whale. At first sight these populations appear to have little in common, however both have a diet more varied than was understood 20 years ago, and both are struggling to adapt to our rapidly changing climate.

Gray whales were once thought to exclusively hoover up amphipods—shrimp-like critters found in the Bering Sea, thus requiring an epic 6,000 mile migration from Mexico calving grounds to these rich cold-water feeding grounds. In the last two decades, as more grays started to detour into Oregon and Washington waters, it became clear their menu is more diverse; visiting Puget Sound to feed on ghost shrimp, Mysid shrimp in coastal kelp forests, even herring off Vancouver Island.

Recent Southern Resident diet studies likewise found a broader menu than was previously known. Though not in great quantities, flatfishes, lingcod, and even skate likely supplement their winter diet when calorie-rich Chinook are less available.

This year’s early arrival of gray whales in Puget Sound is unprecedented, and so concerning. This population was removed from the Endangered Species list in 1994, but has suffered two recent “unexplained mortality events” as once reliable food sources are less readily available in a warmer, more acidic ocean, and consuming lower calorie prey leads to poorer health, and increased deaths; circumstances tragically mirroring the prime threat to our iconic Southern Resident killer whales.

The latest IPCC report chapter 3 ‘Oceans and Coastal Ecosystems’ names gray and North Pacific right whales as the species most vulnerable to a rapidly changing Arctic ecosystem. However, the report rings alarm bells regarding the threat posed to marine mammals in all coastal ecosystems, with impacts cascading through the marine food web as top predators are removed, even due to reduced whale poop!

Salmon are mentioned as a species of concern in Chapter 2 ‘Terrestrial and Freshwater Ecosystems’ given their vulnerability to changes in water temperature, and catastrophic freshwater habitat loss. Over recent years, West Coast salmon have been impacted both by drought and flooding, driven by climate change.

The Southern Residents’ current Endangered Species status is often framed as an “unexplained” 20% decline in their population in the late 1990s; a decline ongoing today. Yet we know this reflects the decline of important wild Chinook populations—calorie-rich, and irreplaceable to this Chinook-specialist community. Seas polluted with forever chemicals and noise, further stress their already fragile health in low Chinook years, resulting in too few births and too many premature deaths.

Just 10 years ago scientists predicted that gray whales might better weather climate change than expected, due to their foraging adaptability, and having survived previous periods of global warming and cooling. Today their future, and that of other whales seems less certain in these unprecedented times. “Unexplained mortality” sure is a misnomer. We do in fact know why; we just lack the political will to enact change to save them, and ourselves. We all rely on healthy oceans for survival.