Whale watching boats do cause stress in orcas but new research suggests lack of prey is a bigger issue for the resident killer whales of the Salish Sea.
credit:
NOAA/John Hogan
Feed me! New research suggests a big stressor for Puget Sound orcas is lack of food. And most of what orcas in the sound is salmon.
credit:
Flickr/mrritter
This time of year thousands of tourists start making their way to the San Juan Islands. Many of them pile onto boats and go out looking for the resident killer whales that are foraging for salmon in Puget Sound.
Scientists used to think all that boating traffic was a major source of stress for the whales.
But new research points to another factor that could be even more upsetting for them.
Katherine Ayres has spent a lot of time analyzing whale poop. She did her PhD work at the University of Washington’s Center for Conservation Biology.
The team there trains dogs to sniff out whale fecal matter when it surfaces and lead the research boat to the site to collect a sample.
Using those samples, Ayres looked at nutrition and stress-related hormones in the orcas to see what’s bugging them. She says those summer whale watch boats aren’t the main culprit.
“So stress does increase with numbers of boats but the key is that it increases in a steeper way when prey is less available,” Ayres says.
When the whales aren’t getting enough food their stress hormones go up.
Chinook - the largest and fattiest type of salmon - makes up almost 90 percent of the resident killer whale diet.
But the runs of chinook in the Northwest are at a fraction of their historic levels.
Ayres says keeping boats away from the whales is important.
“But providing enough prey to support a healthy population should be the first conservation priority for these whales,” she adds.
The orcas returned with a new baby this spring, bringing the population of this endangered group of whales to 85.
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