Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

Observing white shark predation

Along with the variety of surveys we conduct each day on the island ranging from bats to birds to pinnipeds, each person on the island is tasked to spend a few hours at the lighthouse to keep a watch for white shark feeding events. As apex predators in the marine ecosystem, these sharks serve a very important role to keep things in check, but due to their large seasonal movements not a lot is known about them. In the fall, sharks migrate to the coast of California, including the Farallon Islands, to feed on pinnipeds (seals or sea-lions) when the abundance of immature animals is at its peak. This gives us a unique opportunity to study them in a near-shore environment (they spend about half of their year in the pelagic ecosystem) and hopefully garner information about their population trends as well. Not only are the long-term data collected by Point Blue scientists valuable for white shark conservation, but witnessing the sharks is an extremely humbling and incredible experience for the biologists on the island! In the past few weeks, we have gotten the chance to observe a few shark attacks on pinnipeds near the island. Today (September 27), as many migratory birds were circling the lighthouse and a hoary bat flew by Tower Point, a swarm of gulls began to circle in Fisherman’s Bay on the north side of the island. This is often a good sign for a shark predation event, and sure enough, there was a pool of blood below the gulls, indicating that a shark had just found a meal. After gathering coordinate data to later map the location of the attack, I was able to observe the 10-minute long feeding event, with the shark surfacing several times to eat a California sea lion.