30 Days of OCEANS: Naomi Rose

April 28, 2010

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Senior scientist with Humane Society International, Naomi Rose oversees campaigns to protect wild and captive marine animals.  She is also a member of the International Whaling Commission’s Scientific Committee, Her concern for whales and dolphins comes from her transition from field work to desk work. Given recent suggested changes in who can hunt whales when and where, Naomi’s expertise is much in need. An excerpt from our new book, OCEANS, The Threats to the Seas and What You Can Do to Turn the Tide.

Almost twenty-five years ago, a Ph.D. student at the University of California in Santa Cruz, I spent five summers camping on an uninhabited island and bobbing around in a small rubber inflatable boat following the ins and outs of the lives of a pod of killer whales, or orcas, in the waters off British Columbia. These were the Northern Resident orcas, which spend their summers in the Inside Passage of Vancouver Island, particularly in Johnstone Strait. I was interested in the social dynamics of the males, who stay by their mother’s side for life in this population, yet somehow still manage to father offspring outside of the family.

When I was studying these whales, researchers had been taking their photographs – by which these dramatic black and white animals are easily identified – for about 15 years, following individuals year after year. Using actuarial techniques similar to those used by insurance companies, they had determined that the females in this population were, in the words of one scientist, “immortal.”

Obviously this was a bit of an exaggeration, but the fact is that by the mid-1980s, after having followed these individuals since 1973, orca researchers had observed the loss of very few prime-age adult females. Juveniles of both sexes faced many risks and adult males seemed prone to any number of mid-life health crises. However, if a young female managed to make it into adulthood – past the age of 15, more or less, which is when the average female orca starts bearing calves – she was almost certain to live into her sixties, seventies or eighties.

All of that changed in the 1990s.

The change may have simply been a matter of probability. Perhaps in such a long-lived species, fifteen years wasn’t really long enough to gather enough representative data and the seeming immortality of adult females was just what statisticians call an “artifact” of a small sample size (in this case, the small number of years the animals had been followed). Maybe after ten more years of data collection, the dataset was giving a more accurate picture of orca lives. Maybe it was normal after all for a fair number of females to die in their twenties, thirties or forties.

However, other research was showing that deaths, of all sex and age classes of orcas, increased in years with bad Chinook salmon runs. The orcas of British Columbia aren’t marine mammal hunters, but rather specialize in feasting on salmon. And not just any salmon – they are very picky and love the prized Chinook or king salmon. In the 1990s, due to a host of mostly human-caused factors, there had been a number of poor salmon runs. In these years a larger number than usual of Northern Resident orcas were dying, including adult females who should have been in the prime of their lives.

I was shocked when I heard this news, not having been back to British Columbia in almost a decade. The orcas of Johnstone Strait had been frozen in time in my memory, hale, hearty and thriving. It was appalling to hear that the “immortal” females of my graduate career were dying, at the height of their reproductive years, sometimes with a dependent calf left behind to starve. Many of these females had been the sisters and mothers of the males I had studied for my dissertation research, animals I knew on sight, who had names and personalities and histories. And they were dying not in the natural course of things but because human beings were causing the degradation of their habitat (and that of their salmon prey), polluting their bodies with toxins, and over-exploiting the fish on which they depend.