Oil a Killer for Coastal Whales: Enbridge As Orca Champion?

West Coast oil spill would be a killer for whales

Misty MacDuffee and Chris Genovali - Raincoast Conservation Foundation 

Janet loves the orcas. At least that's what Enbridge would have had us believe in its now-aborted Northern Gateway ads that featured the company's vice-president Janet Holder touting how safe oil tankers are for B.C.'s killer whales.

Unfortunately, Janet must not remember what happened to killer whales 24 years ago after the Exxon Valdez grounded on Bligh Reef, or she wouldn't be willing to potentially subject animals she allegedly adores to miserable deaths like those suffered by Alaska's whales.

Prince William Sound, like coastal British Columbia, is home to two types of killer whales: the fish-eating resident whales and mammal-eating transient whales. In many ways, killer-whale reproductive biology is similar to humans; they are long-lived, slow to reproduce, reach sexual maturity in their teens and females typically have fewer than six calves in their lifetime. Resident killer whales will stay in their family unit (linked through the mothers and grandmothers) forever. Each animal is also unique in its markings and fin shape, so it is possible to do a census of the population with great accuracy.

After the Exxon Valdez oil spill, the mortality rate in two pods of Prince William Sound's killer whales skyrocketed. While 33 per cent of the resident whales in pod AB and 41 per cent of the transient ones in pod AT1 disappeared within a year of the spill, most of the carcasses of the 22 missing whales were never found. Even though the whales were absent from their pods, the lack of carcasses made it hard to confirm the whales were dead. But none of the missing whales were ever seen again. Both pods were documented surfacing in the oiled waters, one of which (the AT1 transients) were photographed at the stern of the Exxon Valdez while it was still leaking thousands of litres of oil into Alaskan waters.

The timing and magnitude of missing whales directly following the spill, plus the known exposure, suggests that oil was the cause of death. Other killer-whale pods that were not in Prince William Sound during the spill did not experience the mass mortality (10 times the natural rate) of these two pods. Scientists have hypothesized that these whales died from inhaling toxic oil vapours as they swam through and surfaced in the spill, and in the case of the transients, potentially from eating oiled harbour seals as well.

Unfortunately, many of the whale mortalities were breeding or young females. Although calves have been born into the resident whale population, unexpected mortalities, the loss of important females and a breakdown in the social structure has meant little recovery for this pod of whales.

In the case of the transient population, the loss of the females has meant no new births in more than 25 years. The transient pod is considered functionally extinct, as it will be gone when the remaining individuals die.

Both resident and transient killer whales in B.C. are species of concern under Canada's federal Species at Risk Act. Our northern and southern resident whales are threatened by declining salmon stocks, pollution and physical and acoustic disturbance. Past removal of individuals for the aquarium trade also lowered their numbers and likely has had other social consequences as well.

Like Prince William Sound's killer whales, these small populations are now more vulnerable to extinction. There are three main reasons for this.

First is the role of "chance variability." This occurs when there is a random drop in birth rate, an increase in death rate or repeated offspring of the same sex in a generation, all of which can lead to extinction.

Second, when small populations experience random events such as food shortages, disease or oil spills, the loss of individuals, (especially breeding females) can have dire consequences. This concept underscores the importance of numbers to maintain the resilience and adaptive abilities of populations that face disturbances.

Third, small populations are vulnerable to reduced genetic variation. By their very nature, small populations are a subset of individuals from what was once a much larger population. As small populations breed, the role of chance error in genetic makeup becomes higher. For populations to adapt and evolve with changing conditions, genetic variability must be present. Reducing genetic variation can decrease survival.

So when you see the new Enbridge commercials telling British Columbians "we all want better," keep in mind the very real threat the company's oilsands pipeline and oil-tanker project actually poses to B.C.'s killer whales.

Misty MacDuffee is a biologist with Raincoast Conservation Foundation. Chris Genovali is Raincoast's executive director.