Two populations of orcas, known as the northern and southern populations inhabiting the waters surrounding southern British Columbia and northern Washington, are going missing.

Orca hunting behavior and diet are geographically dependent. As a result, three types of orcas are recognized: resident, transient, and offshore. Although these orca types appear the same, each type has “specific genetic differences and specific food preferences and habits.” The resident orca type are salmon specialists, so declining salmon stocks are probably having a negative impact on these orcas. Certainly there are probably other related factors, but it’s safe to postulate that these animals require their main source of protein—salmon—in order to sustain their massive bodies. “Peanut head,” a term of art describing an orca’s condition, is a sign of starvation, and it has been reported from the area by fisheries observers and researchers. From Canada.com, Canada:

Some endangered southern resident killer whales are developing “peanut heads,” showing they are not getting enough food, said Howard Garrett of Washington-based Orca Network.

“They are looking sick. There is usually a thick layer of blubber just behind the skull, and that seems to be the first place to be drawn from when they need to draw down blubber,” he said. “In some of them, there’s a dip right behind the blow-hole and, when you see that, you know the whale has been hungry.”

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Unusual liaisons are happening as the whales search for elusive chinook salmon, Garrett said.

“A small group from L Pod have been traveling with J Pod all summer long, and twice J Pod has split into two completely separate groups, out of acoustic range from each other,” he said. “It’s an indication that they are searching high and low and in every nook and cranny for fish.”

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The strategy’s objectives are to ensure the whales have an adequate and accessible food supply, that chemical and biological pollutants and disturbance from human activities do not prevent recovery and that critical habitat is protected.

John Ford, marine mammal scientist at DFO’s Pacific Biological Station, is an expert on the eating habits of resident killer whales. Ford wrote last year in a University of British Columbia paper, that “resident killer whales may be dependent on chinook salmon, and the abundance of this prey species may have a direct effect on their survival.”

From the Globe and Mail, Canada:

The northern resident population, which ranges around the northern end of Vancouver Island, has relatively stable numbers. The group has about 200 whales, a decline of about 7 per cent since 2000. But reports this summer indicate the population has been struggling to find food.

The southern residents, a population of 83 whales found in Puget Sound and the southern end of the Strait of Georgia, have been hit harder. Not only have they had few salmon to feed on, but the Center for Whale Research, a U.S. facility that has been studying the population for 30 years, reported last week that seven adults – including two reproductive females – have vanished. Two calves are also missing.

Observers had earlier reported signs of starvation in some of the whales, which develop a distinctive condition known as “peanut head” when they lose weight. And the birth rate has declined – with only one calf born this year.

Dr. Barrett-Lennard said the southern resident population fell to 90 in 2004 from a historic level of about 200 and now is at 83.

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