December 21, 2008
Scientists Investigate Reasons Behind Missing Orcas
Scientists are analyzing killer whale scat and breath samples in the hopes of solving the mystery of Puget Sound's dwindling orca population.
There were seven resident killer whales that frequently pass the waters of Washington that went missing this year and are presumed dead."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.
Researchers of the University of Washington analyzed stress hormones and toxins from scat of the remaining 83 orcas and have found signs suggesting the mammals may have starved to death, possibly because of the dwindling salmon runs.
Another team of scientist from Global Research and Rescue is riding along with whales, using petri dishes on poles to capture air droplets from the blowholes. These samples are being studied for potentially harmful organisms.
One theory for the orcas' demise includes ocean pollutants such as oil and sewage, or vessel noise disrupting their ability to find food.
On San Juan Island, the Center for Whale Research plans to tag the southern population of killer whales next year and track their winter migration. That region's signature whales have been studied for more than three decades, and it's a mystery where they go and what they eat when they leave the Puget Sound.
Next year, researchers will attach satellite tags on the dorsal fins of six orcas. In the past, 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.
Researchers from UW have found a link between whale mortality and low levels of thyroid hormone by using a 2-liter bottle on a telescoping pole to collect whale scat for analysis.
Sam Wasser, director of the UW Center of Conservation Biology, thinks they show a consistent nutritional problem.
Katherine Ayres, graduate student doing work under Wasser, said if whales do not each much, they draw from their fat reserves, where toxins are stored. After that, toxins enter the circulation system and could cause health problems.
She said that it is unclear whether the whales are starving or whether they're becoming more susceptible to disease, but regardless it all goes back to food.
"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 prove 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 find which salmon runs are better for 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."
Hanson and others run the fish scales they collected through a genetic database that allows them to identify the species in a way they were not able to do a few years ago.
Lack of prey may be the only barrier to orca feeding, and vessel noise may disrupt the mammal's ability to find food.
There has been four citations issued under a new state law designed to keep vessels away from whales. Sgt. Russ Mullins of the State Department of Fish and Wildlife, said among the offenders were two different Canada-based whale-watching operations ticketed for coming within 300 feet of the orcas.
NOAA Fisheries is writing new rules for vessels operating in federal waters.
J. Pete Schroeder, a marine mammal veterinarian and director of research with Global Research and Rescue, said lack of food leads to other problems, including increased susceptibility to disease.
Schroeder and others have been capturing breath droplets from whales' blowholes.
They are studying for potential harmful organisms in the thin sea surface layer of the Puget Sound and in the breath samples of the orcas.
Orcas carry at least 13 antibiotic-resistant bacteria, said Schroeder. Pathogens normally live in blowholes and upper respiratory tracts without causing disease, but whales with a suppressed immune system can become infected.
"There are diseases out there that can wipe out this population," Gaydos said.
Schroeder said, all of this collective research will enable scientists to build a health assessment profile for the individual whales.
Advocates argue that orcas' problems should be seen as a call to action to clean up Puget Sound because the whales' decline means something far greater that losing the species itself.
"It means that the whole habitat is losing its ability to sustain life," said Howard Garrett, director of the Orca Network.
On the Net:
- National Oceanic and Atmospheric Administration Fisheries Service
- University of Washington
- Global Research and Rescue
- Center for Whale Research
- SeaDoc Society