Farallones Dispatches: "Double Indemnity: When White Sharks Are The Catch Of The Day"
When a top predator becomes the prey, interesting things begin to happen. On October 4, 1997, whale watchers in NOAA Greater Farallones National Marine Sanctuary off San Francisco witnessed the first-ever documented attack by a transient killer whale named “CA-6” on a white shark. Until then, the debate raged over whether a killer whale’s intelligence was superior to the sheer brute power of white sharks - brain vs. brawn.
Point Blue Conservation Science researchers arrived just after the kill, and with pole-camera and surface observations they captured invaluable information about the whales’ behaviors and relationship between two top predators. The incident ended all doubts about dominance, and similar attacks have since occurred in Australia and South Africa, where killer whales extracted white sharks’ livers with almost surgical precision. But that October day, the real fun in the Farallones was just beginning.
THE MENU: Killer whale (Orcinus orca) sightings are uncommon locally, but three “ecotypes” are recognized: the mammal-eating transients (like CA-6); the shark- and ray-eating offshore types; and the highly endangered Pacific Northwest “resident” killer whales that now venture into our waters in search of salmon. White sharks (Carcharodon carcharias) are our most prominent and intensively studied apex predator. They mainly target young, naïve, blubber-rich butterball elephant seals in the Gulf of the Farallones.
SURF ‘N TURF: The attack itself was astounding. But curiously, it occurred just after the whales had already killed and fed on a sea lion! Ecotypes were expected to adhere to their respective mammal, fish and shark diets. But here was a strange pairing: meat as a main course, fish liver for dessert.
DOUBLE INDEMNITY: These killer whales were winners twice-over: not only did they knock out the competition; their prize was an energy-rich meal of the sharks’ oily liver – “CA6” had shared her kill with running buddy “CA2.” (The elephant-seal crowd must have gone wild!)
WHAT NEXT?!! As it happened, the aftermath was even more intriguing than the kill, especially when the white sharks suddenly fled the scene en masse, and stayed away for the duration of their feeding season. But, the next fall they retuned. The coast was clear.
TOP SECRET: Clearly, a disruption at the top of the food web would have repercussions throughout, especially when an entire contingent of apex predators suddenly decamped. But Pt. Blue’s research, which became part of the Census of Marine Life’s “Tagging of Pacific Predators” (TOPP) project, continued to probe the dynamics and intricacies of this unique food web even more comprehensively. Read the latest TOPP study examining ecosystem-wide consequences of white shark-killer whale interactions: https://www.nature.com/articles/s41598-019-39356-2.pdf.
National Geographic recently premiered “The Whale that Ate Jaws: Eyewitness Report"* chronicling earlier and more recent killer whale-white shark activity around the Farallones and elsewhere, and incorporating TOPP’S research. See related article, https://www.nationalgeographic.com/animals/2019/07/killer-whales-orcas-eat-great-white-sharks/.
PROTECTING THE PREDATOR: In 2009 NOAA Greater Farallones National Marine Sanctuary protected white sharks against disturbance during their brief feeding season here. Unfortunately for the sharks, our jurisdiction doesn’t extend to killer whales. But simply knowing that our waters are so bountiful, that they can support two such magnificent apex predators, gives us justifiable pride and a delicious shiver of respectful fear. Our wild oceans are exemplary self-managed ecosystems, constantly changing; their denizens constantly adapt and innovate, and thereby survive and thrive. When we do intervene on behalf of the surprisingly vulnerable white shark, we’re helping to maintain and restore a natural dynamic.So, continue to support your local marine sanctuary. Explore it, join our Get Into Your Sanctuary Photo Contest at Get Into Your Sanctuary, and consider becoming an active ocean steward.
However you do it, get involved, and show your love for the sea that sustains us.
*“The Whale that Ate Jaws: Eyewitness Report” will air again on the NatGeo and NatGeo Wild channels, so check your local listings.