Unusual Mortality
Over the past few weeks, researchers have discovered over 250 dead sea lion (Zalophus californianus) pups off the coast of Año Nuevo Island, marking an unusual mortality event. Usually, the island sees about 700 pups born annually, with just a handful of deaths, so the current situation is alarming. The high number of deaths, including stillborn and prematurely born pups, has been observed in other parts of the California coast, too.
Various potential causes are being investigated, and while no definitive reason has been determined yet, one theory suspects that changes in ocean conditions, possibly linked to the recent El Niño event, may have disrupted food availability, forcing sea lions to travel farther for sustenance. That could have led to malnourished and underdeveloped pups that couldn’t survive.
This past weekend, I sadly encountered the body of a sea lion pup washed up on the shore at McClures Beach. I don’t know if its fate had been related to the other deaths, but thankfully, there were no others around. In fact, the beach was almost deserted entirely, but I knew the scavengers would arrive soon.
I set up my camera a short distance away and waited on the sand. Soon enough, a common raven (Corvus corax) arrived and began investigating the body. It wasted no time pecking at the fur and starting to feast.
The raven was soon joined by a turkey vulture (Cathartes aura), the clean-up crew I’d expected. They moved cautiously, each leaning in as the opportunity presented itself, but some hierarchy was soon established. The vulture was much larger than the raven, and I expected it to muscle in with ease; surprisingly, the raven seemed to dominate the bigger bird.
After a while, the raven left, and the vulture could eat in peace, using the raven’s work to break the skin. When the raven returned, however, it chased the vulture around, biting its wing feathers and pushing it away. Even when two more vultures arrived, this body belonged to the raven.
As wildlife encounters go, this had been an uneasy, gruesome spectacle, but nature is harsh. The death of one animal nourished many more, who, in turn, worked to clean the beach. The circle of life isn’t always beautiful, but it’s consistently fascinating.
