But there was something about listening to the desperate cries of a juvenile killer whale that had spent at least three weeks stranded in a remote bay off British Columbia's central coast that washed Barrett-Lennard's objectivity away.
"This animal just tore your heart strings," Barrett-Lennard, who runs the Vancouver Aquarium's marine mammal research program, recalled Friday, a day after he and a crew from the federal Fisheries Department rescued the whale and returned it to sea.
"I spent a few nights in the bay and he was calling incessantly, these almost human-like calls and screams. You could really relate to him as a very distressed animal trying desperately, trying to make social contact again."
The killer whale, named Sam, was discovered about three weeks ago by a pair of Fisheries Department researchers who were in the area conducting a whale survey.
The researchers pulled into a bay on Aristazabal Island, located about 550 kilometres northeast of Vancouver,to drop anchor for the night when they noticed the lone whale. They heard the animal's calls throughout the night, but the animal appeared reluctant to leave through the bay's shallow entrance.
That's when they contacted Barrett-Lennard, who arrived about a week later to find Sam in the bay, continuing to call out loudly but still avoiding swimming through the bay's entrance into the open water.
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The whale appeared to be in good condition; it was catching seabirds, but was not seen eating any fish. Transient killer whales typically eat marine mammals such as seals and seal lions.
Barrett-Lennard spent several days attempting to coax the whale out by using an underwater speaker to broadcast killer whale calls outside the bay, but the animal appeared too nervous to leave through the relatively shallow, six-metre-deep section of water.
"He seemed to be very interested in leaving — he'd go right up to the entrance, but he wouldn't cross the threshold," said Barrett-Lennard, who was still in the area and speaking over satellite phone.
"Killer whales are very conservative animals; they're very cautions. I think he was just afraid to go over that shallow area to get outside."
Barrett-Lennard returned to the bay last Saturday, but Sam's condition had deteriorated. Barrett-Lennard said he could see a depression behind the whale's blowhole, which indicates poor nutrition and weight loss.
It was clear something needed to be done.
On Thursday, Barrett-Lennard and a Fisheries Department crew stretched a floating rope across the bay behind the whale, leaving the animal between the rope and the bay's entrance.
Despite their fierce-sounding name, killer whales are particularly nervous creatures, said Barrett-Lennard, and even a rope floating on the surface can be enough to cause a whale to steer clear.
That allowed the crew to use the rope to essentially corral the whale toward the bay's entrance.
"As soon as he was close to the entrance, I played some of his calls back on our underwater speaker, and he shot thought the opening like a cork out of a bottle," said Barrett-Lennard.
"He did a big jump right beside my boat and continued on."
Sam disappeared under the water, but Barrett-Lennard could hear the whale's calls for about 90 minutes before the animal faded away.
A short time later, Barrett-Lennard caught up with the animal again, when he saw Sam near two other killer whales, which were likely the same type of whale but not directly related to Sam.
"He can tag along with them until he finds his family," said Barrett-Lennard.
The aquarium is asking boaters in the area to keep an eye out for the whale and to contact the facility if they spot it.
Barrett-Lennard said it's rare to see a young killer whale away from its pod.
"The family groups are incredibly strong," said Barrett-Lennard.
"These animals stay with their mothers, often for life and certainly until they're much older than this, so it's very unusual for a calf to get off on its own like this."