J-pod attacks on harbor porpoises in July 2005

Cascadia Research Collective, updated July 16, 2005

For more information contact Robin W. Baird

Over the years the fish-eating "southern resident" killer whales in Washington and British Columbia have been seen harassing other cetaceans (Dall's and harbor porpoise) on a number of occasions, with most of the events witnessed by Ken Balcomb and others from the Center for Whale Research. A couple of individual whales from "L-pod" have been responsible for most of these events, although at least one event with K-pod had also been witnessed. While researchers and whale watching operators had logged thousands of hours watching J-pod whales over the years, this behavior had not been documented for J-pod whales.

On July 5, 2005 researchers Monika Wieland and Bob Otis at the Whale Research Lab at Limekiln Lighthouse on San Juan Island witnessed a sub-adult male (J27) from J-pod interacting with a harbor porpoise, pushing the porpoise out of the water. As part of a joint research project between the Northwest Fisheries Science Center (NWFSC) of NOAA Fisheries and Cascadia Research, to study the diet and foraging behavior of southern resident killer whales, we witnessed three interactions between J-pod whales and harbor porpoises over a short period in July 2005.

On July 9 three whales (J16, an adult female, and two of her offspring, J26, a sub-adult male, and J36) were seen chasing a harbor porpoise at high speed in Boundary Pass. The porpoise was seen surfacing six or more times in front of the whales, and all three whales appeared to be involved in the chase. At one point the porpoise was lifted out of the water at high speed by one whale (apparently J16 - see photo below), and on another occasion the porpoise was pushed most of the way out of the water. All three whales and the porpoise then disappeared on a long-dive, and when the whales re-surfaced there was no sign of the porpoise, nor was the porpoise seen again on its own. As part of our diet and foraging behavior study we follow behind the whales examining fluke "prints" for signs of discarded prey, as well as watching the mouthlines of the whales to see if they are carrying anything. In this case none of the whales appeared to be carrying anything in their mouths.

On July 11 researchers Dawn Noren of the NWFSC and Jennifer Marsh of the University of Washington observed three J-pod whales chase a harbor porpoise in Haro Strait. Our research vessel arrived on scene a few minutes later, after the chase was over. The three whales (J11, an adult female and two of her offspring, J27, a sub-adult male, and J39) did not appear to be carrying anything. Several minutes later the three began a chase of another harbor porpoise. Details were very similar to the chase observed on July 9, with the porpoise trying to evade the whales at high speed, all whales involved in the chase, and all going down on a long dive after half a dozen or so surfacings by the porpoise and whales. On this occasion, when the whales came up from the long dive they were not traveling, but were hanging at the surface next to the harbor porpoise, which appeared to be floating dead (see photo below). The three whales pushed the dead porpoise around for a few minutes and then left the area, abandoning the porpoise. The porpoise carcass was recovered after the whales left the area, and a necropsy was undertaken by Joe Gaydos of the SeaDoc Society. No tooth rakes, broken bones or obvious contusions were present, though the exact cause of death will have to await results from the histopathology.

On July 12 Kari Koski of The Whale Museum's Soundwatch Program witnessed J-pod whales chasing a harbor porpoise in Haro Strait, and shortly after we witnessed another chase of a harbor porpoise, by J35, though the outcome of both of these chases were not determined.

It is particularly interesting that a number of different J-pod whales have been involved in these interactions. Why this behavior is occuring is not known, though whether such interactions continue to occur at such frequency over the rest of the summer should help shed light on the behavior, as well as the potential implications to the local population of harbor porpoise. In collaboration with Ken Balcomb of the Center for Whale Research and other researchers, we are preparing a manuscript for publication on these observations. Please contact us with any additional observations of southern resident killer whales chasing or interacting with porpoises.

J16 with harbor porpoise. Photo (c) Greg S. Schorr 2005. Photo taken under NMFS General Authorization for Scientific Research No. 781-1725. Not to be used without permission.

Harbor porpoise being pushed out of water by killer whale. Photo (c) Greg S. Schorr 2005. Photo taken under NMFS General Authorization for Scientific Research No. 781-1725. Not to be used without permission.

J11, J27 and J39 with harbor porpoise. Photo (c) Greg S. Schorr 2005. Photo taken under NMFS General Authorization for Scientific Research No. 781-1725. Not to be used without permission.

J11 and J39 with dead harbor porpoise. Photo (c) Robin W. Baird 2005. Photo taken under NMFS General Authorization for Scientific Research No. 781-1725. Not to be used without permission.

More photos of these interactions may be added over the next few days, so please check back for updates.

More information on killer whales is available on the Cascadia Research web site (www.cascadiaresearch.org/robin/kwindex.htm). For additional information contact: Robin Baird, Cascadia Research (360) 943-7325, e-mail rwbaird@cascadiaresearch.org