Transient orcas
Also known as Bigg's Killer Whales _CJZ2372

Photo of T14 (Pender "O4") by Chris Zylstra, April 27 2008, near Hein Bank.

Photo-identification Catalogue of Bigg’s (Transient) Killer Whales From Coastal Waters of British Columbia, Northern Washington, and Southeastern Alaska.
Dalheim, Marilyn, Paula A. White (2010). Ecological aspects of transient killer whales (Orcinus orca) as predators in southeastern Alaska. Wildlife Biology, Volume 6, No. 3: 308-322.

Barrett-Lennard, Lance G., Craig O. Matkin, John W. Durban, 5, Eva L. Saulitis, David Ellifrit (2011). Predation on gray whales and prolonged feeding on submerged carcasses by transient killer whales at Unimak Island, Alaska. Mar Ecol Prog Ser, Vol. 421: 229-241.
Any attempt to describe transients, or for that matter any community of orcas, presents a challenge because the best way to understand them is by comparison with other orca communities. It's the old conundrum: "Where's the rake?" It's by the hoe. "Where's the hoe?" It's by the rake. Orcas worldwide live as members of ancient sophisticated societies. Each orca community behaves according to traditions and rules that, in their complexity and variability, have no parallel except in human societies (Rendell and Whitehead 2001).

Transient orcas provide a good illustration of orca cultures. In the mid-1970's, Dr. Mike Bigg, the pioneer field researcher on the orcas of British Columbia and Washington State was commissioned by the Canadian Dept. of Fisheries and Oceans to survey the whales to determine how many animals there were. Canada wanted to know whether the whale population could sustain the removal of 10 to 15 animals per year for the marine park industry. Bigg's work showed that the overall population was very small and could not endure such losses, but he discovered much more than just their numbers. He began to notice that in addition to the "normal" orcas (residents) that travel in large pods, there were occasional small groups transiting through, usually only 3 or 4 to a group, traveling erratically close to the rocky shores. He assumed these animals had been rejected by their pods, like the nomadic lions of the Serengeti. So Bigg called them transients.

As the first person to systematically observe these whales, Bigg could not have known that the Pacific Northwest is blessed to provide habitat to two drastically different forms of killer whales, now recognized as living in separate and distinct cultures. In the thirty-plus years since Bigg began orca studies, no migration by either sex from either type into the other has been recorded. Membership in each begins at birth and cultural bonds and identity continue throughout life. Residents and transients differ in diet, vocal traditions, habitat range, morphology (shape of dorsal fin, etc.), pigmentation patterns (such as the eye patch) and genetically. Though they cross paths routinely throughout the inland waters of BC and Washington State, the two forms are becoming, or by some accounts are already, separate species. DNA work indicates that they have not interbred for at minimum one hundred thousand years. Each orca population worldwide seems to follow its own rules to guide their diets, associations patters, behaviors and vocalizations, rather than simply show similarities with either residents or transients. Some researchers have suggested that residents should really be called "fish-eaters" and transients "mammal-eaters."


_CJZ2438
Photo by Chris Zylstra

Transient killer whale pods are generally comprised of an adult female and two or three of her offspring. Among the differences between residents and transients are that while resident orcas of both sexes stay within shouting distance of their mothers their entire lives, only first-born male transients maintain such intense fidelity to their mothers. Optimum pod size for transients is three, so whenever a third offspring is born, one of the siblings often leaves. The rule seems to be that the eldest son can stay, but all but one of the others may have to go.

After departing their mother's company, roving males may join up with other groups from time to time. Females are more likely to join up with other transients, at least for a time. It isn't known if the hosts are relatives. Departing offspring, whether male or female, tend to leave their mother at 5 to 12 years of age.

Orcas have no predators and are capable of ingesting virtually any bite-sized living thing found in the ocean, but residents select only fish (mainly Chinook salmon) and squid to dine upon, while transients never touch a fish or squid, but prey exclusively on seals, sea lions, porpoises, dolphins, and other large whales. Orcas everywhere appear to specialize on certain prey. This way they divide up the available food in the marine ecosystem and avoid competition. Salmon, resident orcas' preferred delicacy, are widely dispersed, so residents are able to travel in large groups across wide expanses. Transients tend to move in their small groups silently, usually around seal haulouts. They silently stalk and outwit their wary food, zig-zaging in unpredictable patterns. The optimum number of orcas in a hunting party is three, since three can most easily detect and surround mammalian prey.

In one transient family, the second-born male offspring (M3) left his mom (M2) at about age 7 when a third offspring (M4), a female, was born. When M4 was about 10 another sibling (M5) was born, and two years later M4 departed, keeping pod size at three. M4 was photographed with another group of transients thousands of miles away, but two years later, after her oldest male sibling (M1) died, she returned to her mother's side, once again bringing pod size back to the prescribed number of three. At least two male transients are usually seen alone, but as yet no solo females have been found.

Residents often seem to celebrate festive occasions and gatherings of pods with repeated breaches, taillobs, cartwheels and spyhops, accompanied by a wide variety of vocalizations. Transients wait until their prey have been subdued before they make themselves known. Occasionally transients may gather in group of a dozen or more and can also be quite acrobatic during socializing sessions. Seals and porpoises may be tossed around like a frisbee, batted into the air with powerful tail slaps, or held underwater until drowned. Orcas probably got their exaggerated reputation as killer whales from reports of transients viciously ripping marine mammals, including large whales, to shreds. To date, however there are no known cases of orcas eating or even harming a human.

About 320 individually identified transient orcas are commonly seen along the coastline of Washington and British Columbia and from Southeast Alaska to California. Gulf of Alaska transients also number just over 300, and a third clan was all but wiped out by the 1989 Exxon Valdez oil spill. Fewer than ten survivors remain in 2009, none of which are reproductive females. These transient communities haven't all been photographed, however, and new adult individuals in the two larger groups are still occasionally documented.

References

Baird, R.W. and H. Whitehead. 2000. Social organization of mammal-eating killer whales: group stability and dispersal patterns. Can. J. Zool. 78: 2096-2105

Baird, R.W. 2000. The killer whale-foraging specializations and group hunting. In: Cetacean societies: field studies of dolphins and whales. Edited by J. Mann, R.C. Connor, P.L. Tyack, and H. Whitehead. University of Chicago Press, Chicago. pp. 127-153.

Baird, R.W., and Dill, L.M. 1995. Occurrence and behaviour of transient killer whales: seasonal and pod-specific variability, foraging behaviour, and prey handling. Can. J. Zool. 73: 1300- 1311.

Bigg, M.A., Ellis, G.M., Ford, J.K.B., and Balcomb, K.C. 1987. Killer whales-a study of their identification, genealogy and natural history in British Columbia and Washington State. Phantom Press, Nanaimo, B.C.

Dalheim, Marilyn, Paula A. White (2010). Ecological aspects of transient killer whales (Orcinus orca) as predators in southeastern Alaska. Wildlife Biology, Volume 6, No. 3: 308-322.

Rendell, Luke & Whitehead, Hal. 2001. Culture in whales and dolphins. Behav. Brain. Sci. v24(2): 309-382

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