From the evidence I deliver in the slideshow below, you’ll see that August 31st, 2011 was not a good day for some rhinoceros auklets (Cerorhinca monocerata) in Johnstone Strait, British Columbia, Canada.
That day, I witnessed a very socially active group of “transient” (marine mammal-hunting) killer whales repeatedly harassing these birds – mouthing them and slapping them. At least 3 juvenile rhinoceros auklets had a bad day and, since these are diving birds, they cannot “alight” and escape the teeth and fins below them. Yet, I believe they survived.
I interpret the transient killer whales’ interaction with the birds to be “text book” play behaviour largely involving the juvenile killer whales. In this case, the text book is Dr. John Ford’s and Graeme Ellis’ Transients: Mammal-Hunting Killer Whales of British Columbia, Washington, and Southeastern Alaska. I provide their expert interpretation of the behaviour below, entitled “Seabirds: Playthings and Practice, or Between-Seal Snacks?”
“It is not unusual to see transients chasing and harassing seabirds. During most of these incidents, the whales do not seem intent on eating the birds. Rather, they let the bird escape or they abandon it after it has been injured or killed. Seabird harassment appears to be a favourite activity of juvenile transients. They young whales will sometimes swim upside down and on their sides, looking for birds paddling at the surface above. Once a victim is sighted, they will try to slap it with their tail flukes, jump on it, or seize it in their mouth. This interaction may continue for several minutes, before the bird is eaten, incapacitated, or left dead in the whale’s wake. We and others have recorded at least 10 seabird species that have become casualties of transients. Frequent victims are common murres, which are flightless for several weeks during the late summer and are like “sitting ducks” for transients. Other species include black brant, common loon, white-winged scoter, surf scoter, cormorant (species uncertain), western grebe, marbled murrelet, rhinoceros aucklet, and red-breasted merganser. Seabirds seem to be more important as objects of play or harassment than as a dietary item. Juveniles playing with seabirds no doubt learn useful skills in prey capture and handling that may enhance their success in hunting harbour seals and other wily prey.” Source: Ford, J.K.B., and Ellis, G.M. 1999. Transients: Mammal-Hunting Killer Whales of British Columbia, Washington, and Southeastern Alaska. UBC Press, Vancouver, and U. of Washington Press, Seattle. 96 pp
I personally had never seen such a prolonged display of this transient killer whale play behaviour before. In fact, I had never seen transient killer whales socialize quite so rambunctiously!
In the Northeast Pacific, “transient” killer whales (or “Bigg’s killer whales” – after the late Dr. Michael Bigg) are believed to have diverged from the “resident” (inshore fish-eating) and “offshore” (offshore fish-eating) killer whales some 700,000 years ago (Morin et al, 2010), to refine a culture of stealth and unpredictability in order to hunt their marine mammal prey.
But clearly, when their bellies are full and social needs dominate, this type of killer whale is anything but stealthy. On August 31st, this incredibly socially active group of 20+ transients took about 1.5 hours to travel only +/- 4.5 km (2.5 nautical miles) – slapping birds, rolling over one another, tail slapping, vocalizing and breaching along the way. The whales would go on to bound past the community of Alert Bay, Cormorant Island. I have have previously written about this in the blog item “Might As Well Jump.”
Jared Towers of the Department of Fisheries and Ocean has confirmed the IDs of the transient killer whales in the August 31, 2011 encounter to be: T010s, T034s, T035s, T037s, T046Bs, and T146s.
Photos taken while on board with Orcella Expeditions.
See “surplus killing” pp. 167 Barrett-Lennard, Lance. Heise, Kathy A. The Natural History and Ecology of Killer Whales – Whales and Whaling