Killer whales and the scientists working to save them
August 12, 2014
There is no documented case of a wild orca killing a human. It’s time we returned the favor by protecting the health, habitat, and viability of this highly intelligent, vocal, social and powerful species.
Orca face many threats including degradation of their hunting habitats, overfishing of their food, disturbance from sea vessels, warming oceans, and chemical pollution. They are exposed to toxic chemicals, some of which have been banned for decades and some in current use.
[British Columbia’s] killer whales are now among the most … PCB contaminated marine mammals in the world. While the “legacy” PCBs have largely been banned, … PBDEs have recently emerged as a major concern. The endocrine-disrupting nature of these two persistent fire retardants in biota spells trouble at the top of the food chain, with increasing evidence of effects on reproductive health, the immune system, and development in exposed mammals.
As the ocean’s top predator, orca ingest the pollutants their prey have consumed along the food chain. In British Columbia, “resident” killer whales eat fish, especially salmon, while “transient” orca eat highly contaminated marine mammals, such as seals and sea lions. As a result, Dr. Ross finds “transient killer whales are more PCB-contaminated than their fish-eating resident counterparts, reflecting their higher trophic level.”
A hemisphere away, the scenario is different. In New Zealand, pollutants settle in the sediment of harbors in industrial areas. The pollutants are ingested by filter feeders like scallops. Contaminated scallops are eaten by bottom feeders like rays, which make up 80% of New Zealand killer whales’ diet. So it’s not surprising that blubber samples from two dead orca showed very high levels of PCBs and DDT, putting New Zealand orca among the most contaminated marine mammals in the southern hemisphere.
The PCBs contaminating these animals have been banned for decades, but PBDEs, flame retardant chemicals in current use, have a similar structure. Like PCBs, PBDEs are toxic and accumulative. They are also lipophilic or “fat-loving” so they accumulate in blubber and fat-rich breast milk.
Male orca accumulate these chemicals throughout their long lives (up to 50 years) and are more PCB-contaminated than females. Females live longer (up to 85 years) but they transfer large amounts of their chemical burden to their calves through the placenta and breast milk.
Might this reduced chemical burden account for females’ longer lives? Might it explain why first-born calves have reduced life expectancy? Noting that females first give birth at around age 15, Peter Ross answers the second question saying,
We have no way of knowing whether this is due to contaminants (they do receive 15 years’ worth of accumulation compared to 3-4 for subsequent calves), or to inexperience on the part of the mothers (who are typically smaller as well).
Another marine biologist studying killer whales is Dr. Ingrid Visser, Founder and Principal Scientist at the Orca Research Trust. Dr. Visser is The Woman Who Swims with Killer Whales featured on BBC’s Natural World. In the documentary, she works alongside fellow Kiwis trying to save a pod of stranded pilot whales; rushes to rescue an exhausted humpback tangled in fishing net; and races to the latest orca sighting, dons her snorkel and plunges into the water to swim with New Zealand’s wild killer whales. With a population of less than 200 orca, Dr. Visser warns, “If we had one environmental disaster, one oil spill, we could wipe out the whole population. They’re right on the brink.”
Despite years of protection since being listed as critically endangered, New Zealand’s orca population shows no sign of growth. Why? And do the very high PCB and DDT levels found in the two dead orcas’ blubber samples explain a high number of orca deaths?
The samples were sent to Peter Ross for analysis. He noted these chemicals are “not acute poisons” and are “highly unlikely to poison any of these animals but these concentrations could weaken the animals or alter their growth and development. There might even be a risk of adverse effects on the reproductive health of both males and females.”
PBDE levels in the dead orca were relatively low compared to orca in other parts of the world, but flame retardant use is increasing in New Zealand as it is globally. In North America, concentrations of PBDEs in some species are doubling every 3-5 years.
Dr. Ross says, “PBDEs are slated to become one of the pre-eminent POPs [persistent organic pollutants] of the century.”
Dr. Visser notes flame retardants are insufficiently regulated and pledges, “It’s going to be a long haul trying to get some regulations in place for the flame retardants but I think it’s worth it… I’m not going to rest until [the orca are] better protected.”