Scientists struggle to find reasons behind gray whale deaths

Some researchers think the whales are starving, but the cause of death may be far more complicated.

 

Scientists are monitoring the lives of grey whales in the Chukchi Sea to determine if the deaths could be part of a larger trend as animals struggle to adapt to climate change.
Nicholas Metheny/NOAA/NMFS Permit No. 20465

On July 2, around a thousand feet above the Chukchi Sea, Megan Ferguson sat with two scientists in the back of a small propeller plane. Bounded on the east by Point Barrow, Alaska, and on the west by Wrangle Island, north of Russia, the Chukchi serves as the summer feeding ground for hundreds of gray whales. This year, a disconcerting number of them are not completing their journey north. Along the West Coast of Mexico, the United States and Canada, at least 193 dead animals have washed ashore — the most in two decades.

The plane cut through clouds and fog, curving around Alaska’s northwestern coast as the research team searched for the 90,000-pound creatures. Through the overcast, a scientist at a side window spotted a gray whale. She opened the window, aimed her camera and photographed it, while Ferguson, a co-leader of an Alaska Fisheries Science Center research team,jotted down its location and behavior. By tracking the whales’ numbers, physical condition and eating patterns over a four-month period, the team can compare them to those of other gray whales in different areas. Ideally, that will help them uncover what is happening to this species. 

So far, the cause of the die-offs remains a mystery, though theories include starvation from lack of food, or a disease that mimics chronic wasting disease. Teams of scientists are investigating what the casualties mean for the gray whale population as a whole. But some also fear that the deaths could be part of a larger trend as animals struggle to adapt to climate change. Said Ferguson: The “gray whales are just one piece” to the environmental puzzle.

A thousand feet above the Chukchi Sea, Ferguson rides with other scientists to track the ambiguous cause of recent whale deaths.
Megan Ferguson/NOAA

This isn’t the first time marine biologists have seen large numbers of gray whales wash up on shore. In 1999 and 2000, around 630 whale carcasses were reported in Mexico and the United States. The deaths happened during their annual migration, when the whales travel 10,000 miles round-trip from their breeding areas in the warm waters of Baja California, Mexico, to their feeding grounds in the cold Arctic seas. At the time, scientists speculated that the deaths were caused by starvation, disease, ship strikes or some combination of the three, but no firm conclusion was reached.

Today, many of the whales washing up along the coast in California, Oregon and Washington look malnourished with blubber that lacks a healthy, oily shine. That was true of a dead whale on the rocky coast of Port Hadlock, Washington, whose stomach was filled with eelgrass. The presence of eelgrass, which grows on muddy ocean bottoms where whales typically suck up amphipods — microscopic ocean critters that may be struggling due to changing ocean conditions — suggests that the whales may have been desperately trying to eat but not finding the foods they typically rely on.

A gray whale carcass on the shore south of Point Lay, Alaska, in the northeastern Chukchi Sea. It is one of at least 193 that have washed up recently.
Lisa Barry/NOAA/NMFS Permit No. 20465

But in Alaska, Ferguson isn’t seeing signs of starvation. Instead, her aerial photos show normal-looking gray whales. There is the possibility that emaciated whales are dying before they reach Alaska, but that’s a working hypothesis and there’s still a lot of data to be collected, she said.

Sue Moore, an affiliate professor in biology at the University of Washington who studied the mass dies-offs two decades ago, thinks more is involved than malnutrition. Moore noticed that, just like last time, not all of the dead whales look the same, indicating that the cause of death may be more complicated. Their symptoms mimic chronic wasting disease (CWD), a deadly neurological condition that mainly affects hoofed mammals like deer, elk and moose. Once the disease reaches the brain, animals’ display abnormal behavior and start to starve, which eventually leads to death.

According to Trent Bollinger, a CWD expert at the Canadian Cooperative Wildlife Health Center, the chances of the whales having CWD are slim —but they may have a neurological disease with similar symptoms.  Moore would like to collect fresh tissue from the whales and test for an array of diseases and viruses.

The gray whale deaths also reflect a larger issue — the impact of climate change on the ocean. Arctic animals in particular are struggling to adapt to warming waters. For example, Alaskan salmon have been suffering from heart attacks caused by rising water temperatures, with some areas reaching all-time highs. Additionally, amphipods, one of the gray whales’ main food sources, may be at risk from a loss of oxygen in warmer Arctic waters. Since the mid-1900s, ocean oxygen levels have decreased on average by two to five percent. “This is a broader story,” Moore said. “I think something big is going on.”

For Ferguson, who is now flying out of remote Deadhorse, Alaska, the photos collected are key in helping investigative scientists reach a conclusion. Every year, something happens in the ocean that we couldn’t predict, said Ferguson. “We are definitely entering new and uncertain territory.”

Helen Santoro is an editorial intern at High Country News. Email her at [email protected] or submit a letter to the editor.

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