In the waters off Alaska, populations of Aleutian sea otters and Steller sea lions have been declining at alarming rates over the last few decades, some by as much as 80 to 90 percent. But who or what is responsible for these declines? The search for an answer to that question has led to a rather unlikely scapegoat: orcas.
Some scientists are pointing their fingers at this marine mammal, who is also known as a killer whale. And the media, the fishing industry, and certain members of Congress have leaped at the chance to indict something other than human activity. After all, each one of these groups has a self-interest in buying into the orca theory: Legislators have political cover from powerful fishing industries, fisheries can continue their unsustainable practices, and journalists can spin a bloody tale of "voracious" orcas destroying ecosystems.
But the danger of this theory, The HSUS believes, lies not only in the possibility of orcas unfairly taking the blame for population crashes of other marine species, but also in the possibility of government-sanctioned culling programs specifically targeting these whales.
Where It All Began
A highly publicized scientific hypothesis is the source of much of this drama. Starting with a 1998 article in Science magazine, Dr. James Estes, a sea otter biologist at the University of California, Santa Cruz, and associates have been publicly speculating that some orcas in Alaska are "fishing down the food chain"—that is, eating smaller prey (such as Steller sea lions and Aleutian sea otters) than they have in the past. Transient orcas, who regularly eat marine mammals, are the focus of this hypothesis rather than the more frequently seen resident orcas, who primarily eat fish.
The theory presupposes, of course, that transient orcas were forced to abandon a previously favored food source. According to Estes and his colleagues, that source is large whales.
The researchers point out, correctly, that whaling wreaked havoc on species such as fin, gray, and humpback whales. Estes and colleagues go on to speculate that the reduction in whale populations was so dramatic that Alaskan orcas were forced to prey on smaller marine mammals to survive. Once the orcas ate through the mid-sized Steller sea lion and harbor seal populations (the latter have also crashed in Alaska in the last two decades), the researchers theorize that the orcas had to focus on the relatively tiny and lean otters. (Sea otters have little blubber and rely on their thick fur for warmth.)
What this theory has in its favor—at least when it comes to grabbing headlines—is that it provides a simple solution to a serious problem. What it lacks is evidence. Numerous biologists have pointed out that the hypothesis is not backed up by any direct evidence that transient orcas have caused local Steller declines or, for that matter, that orcas have historically preferred to eat large whales.
Indeed, some whale species, such as the minke, were never much reduced in the waters near Alaska. Others, such as the gray whale, have staged a remarkable comeback since commercial whaling was banned—a comeback that occurred roughly at the same time as Alaskan sea otters and Steller sea lions were declining. So, scientists wonder, why would orcas continue to focus on otters and sea lions if their favored food is in abundant supply?
Scientists have another question, too: If the presence of transient orcas translates into declining populations of smaller marine mammals, why then are so many seal and sea lion populations thriving along the west coast of the United States where transient orcas prey upon these animals with a frequency similar to that seen in Alaska?
Many scientists agree that the likely causes of the marine mammal declines are overfishing, global warming or pollution (or some combination of the three), rather than the presence of predators who have co-existed with sea lions and otters for millennia. Human activities simply have a much heavier impact on the marine environment, particularly at the poles. (Think: ozone hole.)
Furthermore, orca biologists tend to dismiss the "fish down the food chain" theory. In fact, preliminary research on the ecology of orcas indicates that Alaskan marine mammal declines should not be attributed to orcas without more data. In an interview with the Anchorage Daily News (May 19, 2002), Dr. Craig Matkin, who has been studying orcas in south-central Alaska for almost 20 years, said, "I'm really uncomfortable with applying this cascade hypothesis to killer whales across the whole region&There's just not enough evidence yet."
Matkin and other biologists are conducting the first significant research on orca population biology and feeding habits in western Alaska. In an interview on Arctic Science Journeys Radio (February 7, 2003), Matkin said, "It's too short a time to make any grand pronouncements. But certainly we haven't found anything in this first year that would push us farther toward thinking that killer whales are the big problem or were the big problem in the sea lion decline."
The radio show reported last summer that the researchers observed approximately 460 resident (fish-eating) whales, while spotting only about 23 transient (mammal-eating) orcas. Matkin commented that, "It's pretty ironic that 65 percent of our encounters with transient killer whales are in southeast Alaska [while in western Alaska, where the Steller population has declined by 80% or more, less than 10% of encounters are with transients]. Yet the population of both harbor seals and Steller sea lions is either stable or increasing [in southeast Alaska]." The Media Runs with the Story
Latching onto a good story, the media seem to have bought the Estes theory hook, line, and sinker. They perpetuate a villainous and dangerously misleading perception of orcas with headlines such as "Killer Appetites in Western Alaska" (Marine Mammal News, April 7, 2003) and "From Ocean Icons to Prime Suspects: Orcas Devastate Seal, Otter Populations" (Washington Post, April 12, 2003).
In the Washington Post article, orcas were said to be going on a "species-threatening rampage" in Alaska, where they are "wiping out" Steller sea lions and Aleutian otters. The article stated that harbor seals in Washington state were "traumatized" by predatory orcas.
In discussing drastic marine mammal declines, however, the Post reporter doesn't even mention the widespread negative impacts of overfishing, climate change, or oil spills. Furthermore, the Post article fails to include the perspective of large whale biologists, many of whom find it absurd to suggest that orcas prefer to hunt large whales and that, when those whales aren't available, will "devastate" other marine mammal populations. (These biologists note, for example, the absence of evidence such as scars, which surely would be found on many whales if orca attacks were common, taking into account that not all hunts would be successful.)
"The over-dramatization of a natural behavior such as predation is a disturbing and inaccurate form of environmental 'education'," says Dr. Naomi Rose, marine mammal scientist for The HSUS. "It is irresponsible for a newspaper to state pure conjecture as fact, especially in an article's headline. These stories may well influence politicians, in both Alaska and Washington, D.C., giving some a pretext for shifting the discussion focus of marine mammal declines from destructive human activities to a 'voracious' natural predator whose numbers may very well need to be controlled.
"In short," Rose adds, "these inflammatory articles may lead someone to propose an orca culling program to save the Alaskan ecosystem."
Stellers and Otters
Steller sea lions and Aleutian sea otters are just a few of the marine species in Alaska that have declined at alarming rates. Populations of harbor seals, fur seals, and sea birds are also crashing. This kind of widespread impact is indicative of the collapse of an entire marine ecosystem.
The western population of Steller sea lions has declined by almost 80% over the last few decades. In 2000, the estimate for the western Steller population in Alaska was a fragment of what it used to be: 34,600 animals, down from approximately 180,000 animals observed in the 1950s. Steller sea lions in the western Aleutian Islands region are of particular concern: The decline in pup counts from 1998 to 2002 was greatest (down 39%) in this region. This decline has paralleled a tremendous increase in high-volume trawl fisheries targeting sea lion prey species in critical habitat areas.
In 2001, estimates of sea otters in Alaska were at about 75,000 animals, having dropped by at least 25% since the mid-1970s when their population was estimated to be at around 100,000 to 150,000 animals. In the Aleutian Islands, the population has shrunk by about 70% since 1992, down to approximately 8,742 animals in 2001. The decline has been even more precipitous in the southern Alaskan peninsula, where the population was estimated to be about 1,844 sea otters in 2001, down approximately 91% since 1986.
The True Culprit(s)
What is responsible for such dramatic declines? The HSUS's Rose points to the excessive and wasteful commercial harvesting of fish.
"It's a matter of record that during the decline of the Steller sea lion, the National Marine Fisheries Service (NMFS) repeatedly failed in its responsibility to protect these animals and their habitat," Rose notes.
Instead, Rose adds, NMFS for decades held the door open for the enormous expansion of industrialized commercial fisheries, which have depleted fish stocks critical to the survival of Stellers and other marine species. "The development of one of the nation's biggest and most valuable fish catches has come at the cost of the integrity and diversity of one of the nation's most invaluable ecosystems," Rose says.
Other possible causes of sea lion and otter declines in Alaska range from climate change and environmental contaminants to nutritional stress and subsistence harvests. But it is clear that orcas and their prey have coexisted for millennia, Rose re-emphasizes, and that orcas are highly unlikely to be the primary driving force behind these severe declines in Alaska.
"If society is looking for a cause of these declines," Rose says, "the most obvious candidate is the activities of humans. It may be appealing for some to point the finger at orcas, but it would also be bad science, bad management, and cowardly politics."
