SEATTLE | Using petri dishes attached to long poles and a trained dog that sniffs for feces, scientists are analyzing killer whales’ scat and breath samples in the hope of solving the mystery of Puget Sound’s dwindling orca population.
Seven resident killer whales that frequent the inland waters of Washington state 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 the feces 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 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 off 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 the salmon harvest in other areas, such as California and Alaska, he said.
UW researchers who use a 2-liter bottle on a telescoping pole to collect whale feces 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The results are still preliminary and unpublished, but Sam Wasser, director of the UW Center for Conservation Biology, said they show a consistent nutritional problem.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 Mr. 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.
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 understand which salmon runs are important to the orcas.
“We’re taking a long hard look at which runs correlate with births and deaths,” Mr. Hanson said. “That has tremendous implication for our ability to improve conservation.”
Once they’ve collected fish scales and other remains the orcas leave behind after feeding, Mr. Hanson and others run it through a genetic database that allows them to identify the species in a way they weren’t able to a few years ago.
The lack of prey may not be the only barrier to orca feeding. Vessel noise may disrupt the mammal’s ability to find food.
To date, four citations have been issued under a new state law designed to keep vessels farther away from whales. Among the offenders were two Canada-based whale-watching operations ticketed for coming within 300 feet of the orcas, said Sgt. Russ Mullins of the state Department of Fish and Wildlife.
NOAA Fisheries is also writing new rules for vessels operating in federal waters.
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