With the help of Tucker, a dog that can smell killer-whale scat from more than a kilometre away, researchers have learned that orcas become stressed by a lack of salmon, but not so much by tour boats.
The study, the first in the world to use a dog to find killer whale feces at sea, is good news for whale-watching guides, who in the past have been accused of harassing whales in the Salish Sea, near the southern tip of Vancouver Island. But it is not so good for the orcas because the salmon they like most – Chinook – are on the decline in the Fraser River.
"We need vastly more food to feed these whales," said Katherine Ayres, lead author of University of Washington study that used the skills of specially trained "scat detection dogs" to test two opposing hypotheses. One theory is that inadequate prey has caused the endangered southern resident population of killer whales to drop to just 88 from a historic high of 200. The opposing view is that vessel traffic is to blame because whale-watching boats that shadow the pods all summer stress animals and disrupt feeding patterns.
To find out which theory was correct, Ms. Ayres wanted to measure stress levels through hormones in fecal samples. To do that she needed to collect a lot of fresh whale scat, which floats only briefly before sinking.
That's where Tucker came in. The eight-year-old black lab, who comes to work dressed in a K-9 Ruffwear lifejacket, with goggles to protect his eyes, is one of a small group of dogs trained by the Conservation Canines program at the University of Washington.
Tucker, like most the other dogs in the program, was adopted from an animal shelter. He was trained to find the scat of wolverines, wolves, moose and woodland caribou, before the killer-whale assignment came up.
The use of dogs to locate wildlife scat was pioneered in 1997 by Samuel Wasser, director of the Center for Conservation Biology at the University of Washington, who modified methods the Washington State Department of Corrections developed to train dogs to find narcotics.
The dogs, which are for hire, are said to be better than remote cameras, radio collars, hair snags or trapping as tools to help wildlife scientists gather material in the field.
"No other method can acquire such a vast amount of reliable information in so short a time," the Conservation Canine website brags of its dogs, which have been used to track the scat of everything from giant anteaters to Pacific pocket mice.
Finding feces is important to researchers because the material is loaded with genetic, physiological and dietary information.
"He was really good at it," said Ms. Ayres, who with Tucker's help was able to scoop up 150 samples over six months.
Tests showed the stress level in whales were lowest in the summer when the number of whale-watching boats were highest and when the salmon run to the Fraser was peaking. When fish were scarce, the stress levels climbed.
Ms. Ayres said more study is planned to look at the cumulative impact of boat traffic, but the conclusion is that having too few salmon around is far worse for killer whales than having too many boats.
She said the study wouldn't have been possible without Tucker.
The dog rode in the bow of the research boat, and the researchers literally followed Tucker's nose, said Elizabeth Seely, a dog handler with Conservation Canines.
Ms. Seely said Tucker was trained first on land, and then by sniffing out a bowl floating in water, with a sample of scat inside.
"We gradually extended the range," she said. "Right now Tucker can detect killer whale scat from a mile away."
She said they didn't know what to expect when they began to train Tucker to find whale scat, bobbing in the waves.
"It amazes me every time we find a sample," Ms. Seely said. "I cannot believe what this dog can smell."
She said Tucker lets her know when he's hot on a scent.
"The more excited he gets, the closer we are," she said. "When we get really close he does this crazy bob and starts running all around the boat."
His big reward for finding whale scat?
"He gets to play with a ball on a rope," Ms. Seely said. "He throws it to himself and whacks himself in the head with it."
The research paper was published on Wednesday, in PLoS ONE, a leading journal published by the Public Library of Science, a nonprofit organization.