Seven resident killer whales that frequent the inland waters of Washington went missing this year and are presumed dead, and researchers want an explanation.
"We're losing animals and we don't exactly understand why," said Brad Hanson, a wildlife biologist with the National Oceanic and Atmospheric Administration Fisheries Service.
University of Washington researchers analyzing stress hormones and toxins from scat of the remaining 83 orcas have found signs suggesting the mammals may be starving, possibly due to dwindling salmon runs.
A different team of scientists from Global Research and Rescue is riding alongside the whales, using petri dishes on poles to capture air droplets from the blowholes. The breath samples are being studied for potentially harmful organisms.
Other theories as to the orcas' demise include ocean pollutants such as oil and sewage, or vessel noise disrupting their ability to find food.
The Center for Whale Research on San Juan Island plans to tag the southern resident population of killer whales next year to track their winter migration. While the region's signature whales have been studied for more than three decades, it's a mystery where they go and what they eat when they leave the Puget Sound.
Starting next year, researchers will attach two-inch satellite tags on the dorsal fins of six of the orcas. For the past seven years, two of the pods have been showing up in central California, an indication they may be foraging farther for salmon.
"We've got to think bigger about the whole food issue," said Joe Gaydos, a wildlife veterinarian and regional director of the SeaDoc Society.
What the whales eat when they leave Puget Sound has implications for salmon harvest in other areas like California and Alaska, he said.
UW researchers who use a 2-liter bottle on a telescoping pole to collect whale scat for analysis have found a link between whale mortality and low levels of thyroid hormone, which partly controls metabolism. When whale deaths are up, thyroid levels are down, suggesting that the whales are starving.
The results are still preliminary and unpublished, but Sam Wasser, director of the UW Center for Conservation Biology, said they show a consistent nutritional problem.
When whales don't eat much, they draw down their fat reserves, where toxins are stored, said Katherine Ayres, a graduate student doing work under Wasser. When that happens, toxins enter the circulation system and could cause health problems, she said.
It's unclear whether the whales are strictly starving or whether they're becoming more susceptible to disease, but it all goes back to food, she said.
"The future for the fisheries is grim, and it's going to get worse," Balcomb said. "I expect that we'll have a worsening of the whale situation."
Studies show orcas prefer Chinook salmon, a species listed as threatened or endangered in several waterways in the northwest, including Puget Sound and the Columbia River.
Scientists are trying to better understand which salmon runs are important to the orcas.
"We're taking a long hard look at which runs correlate with births and deaths," Hanson said. "That has tremendous implication for our ability to improve conservation."
