The video above from NatGeoTV.com presents a theory that a killer whale from the L.A. Pod of orcas might have used tonic immobility during a 1997 attack on a great white shark at the Farallones. The theory suggests that the orca (identified as “CA2″) potentially rammed the unsuspecting white shark, stunning it. While the shark was still disoriented the orca could have either grabbed the great white while it was on its back or flipped it over. The orca could have then held the shark upside down in its jaws, keeping it in a state of tonic immobility until the shark drowned.
While there is no hard evidence or clear-cut video footage of orcas inducing tonic on sharks in the NatGeo feature, the video does include video evidence of killer whales attacking stingrays in New Zealand using a similar technique. As seen in the footage, the killer whales approach the rays upside and grab them with their mouths, then right themselves, so that the rays are upside-down and effectively immobilized. Researchers hypothesize that if orcas have learned to use this technique on rays, then it’s not far-fetched to assume they could use a similar technique on sharks.
On a side note, some of the underwater footage of the “great white shark” in this clip features a shark that is clearly not a white shark. While I admittedly am not great at identifying certain species of sharks, I’m guessing the footage features either a lemon shark or a bull shark. Anybody care to enlighten me on the species seen at around 3 minutes in?
Thanks to DeepSeaNews.com for the video find.