Scientists catalogued the highest number of dead marine mammals in over a decade on the North Coast’s beaches last month — almost triple the typical monthly average.

Twenty-eight marine mammals were found dead last month. Researchers usually find 10 in July, Dawn Goley, the director of Cal Poly Humboldt’s Marine Mammal Stranding Program, told the Outpost. Most of them were seals and sea lions, but at least two dead humpback whales were included too. The program has tracked dead marine mammals over a 140-mile stretch of coastline from northern Mendocino County up into Del Norte since 2012, checking out the same spots at the same times to ensure consistency. 

It’s too soon to tell what’s causing the inflation, Goley said, and many of the animals are too decomposed to examine anyway. This year’s El Niño hasn’t gathered enough strength yet to heat coastal waters close to shore, but it’s getting warmer further out to sea. The ocean also sometimes suffers through heat waves, which have become more common over the last five-ten years, Goley said. Boat strikes may have killed some of them. Some may have starved. Researchers don’t have exact data on the amount of living creatures here either; an increased sea lion and seal population, as well as increased boat traffic, might be driving the rate up as well. “But,” Goley said, “Given the magnitude of it, something else, something unique, is going on this year, and I’m sure it has to do with environmental changes.”

Grey whales have died this year at a higher rate than normal as well, Goley said. Some have starved, or become so emaciated they were unable to recover from injuries. There was another spike in grey whale deaths five years ago, so the stranding program and NOAA are working together to determine why they’re starving. It’s a “complicated” issue, Goley said, but there’s likely a human element. 

They’re also paying close attention to the Guadalupe fur seal, which migrates up here from Mexico to feed offshore. Their population is depleted further south, and strandings here could mean trouble down there. California and steller sea lions seem to be doing OK.

Keeping track is difficult, Goley said. If you see a stranded marine mammal on the beach, Goley wants you to contact them, either by emailing marinemammals@humboldt.edu, or by calling 707-826-3650.