AUDIO:
Hear orcas talking to each other and searching for salmon.
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Showing up early for an appointment at the psychology department, a visitor hesitates before knocking on the door. From inside the office come these…watery gurgles. A captive mountain stream? The professor gargling? Also audible are faint whistles, and the occasional series of clicks. The visitor doesn’t want to interrupt something private, possibly intimate, but he’s in the right place, Buckley Center, and he has this appointment, you see, and so he knocks, and...
...finds the smiling psychology professor Mark Krause, who explains that sounds issuing from his computer monitor are “the vocalizations of whales.” The gurglings are ambient seawater, the whistles are whale talk, and the clicks are echolocation — the sonic probes of killer whales (Orcinus orca) in search of salmon.
“The signals emerge from the whale’s brow,” says Krause, “to bounce off prey and echo back through the lower jaw to register in the whale’s middle ear. Like bats,” he says, “whales use sonar to find their feed.”
Krause has just returned from three weeks on the Gulf of Alaska, where he and a colleague made these recordings. His purpose is to explore predator-prey interactions between orcas and salmon. Now that he has these killer whale vocalizations, Krause will return, in subsequent summers, to play back those recordings amidst natural gatherings of salmon, to see how they react. Later, with luck, he’ll see some actual predation.
Have salmon evolved the capacity to detect the presence of orcas based on auditory signals alone?
Like any pioneer, Krause is eager to find out.
At the close of the spring term Krause was at sea, riding a 45-foot dual-diesel cabin cruiser rigged for research from Seward, Alaska, out Resurrection Bay and into the gulf, an hour and a half seaward but still within view of the stark cliffs of the Kenai Fjords. Dall’s porpoises rollicked alongside the boat and darted past the bow.
“Our vessel was owned and operated by the Alaska Sealife Center. Their funding comes partly from the Exxon Valdez. Oil-spill money. They were immensely helpful at finding the whales. The weather was great. Sunny. We lucked out. The only problem was large ocean swells. You have to be careful not to block the whales’ path. Don’t harass them. Wait until there are no other boats within a couple of kilometers. Then shut our own engines off. Drift with the whales. Drop the hydrophone into the water at the tip of a 25-foot cable. These guys are pretty noisy. Our receiver, on board, was an amplifier wired to an MP3 player, powered by two 12-volt car batteries.” As he recorded, Krause compared the whales’ feeding patterns to what he already knew. These resident orcas like to forage in coves. They prefer chinook, will eat silvers, avoid pink. Pink salmon probably don’t carry enough oil. The nutritional return is not great enough to reward a whale’s effort.
“The clicks and whistles are coded information. We’ll want to know how, or whether, that information gets decoded by the prey.”
Drifting with whales is only a more sophisticated extension of what Krause has been doing all his life. He grew up monitoring wildlife in farm country, his dad the president of a fruit growing company in the San Joaquin Valley. At 15, Mark moved with his family to central Washington and graduated from Yakima’s Eisenhower High School with an affinity for rivers and woods and wild creatures.
“Ever since I was a kid,” says Krause, still lit up like a kid, “I had my eyes on the ground. As opposed to birders, I guess, I scanned the ground.”
Scuffling through fields, seeds hooked to his socks, Krause puzzled over caterpillars, questioned beetles in rotting bark, and captured blue-bellied lizards for inspection.
“Tubing the Yakima River and exploring the valley, I’d come home with snakes. I collected snakes. I’d started with garter snakes and gopher snakes back in California. I had a huge collection of snakes. Up north here I got curious about rattlesnakes.” He earned his bachelor’s and master’s degrees at Central Washington University and began studying to be a vet, but got nudged into pure research by good psychology professors and the school’s fine collection of signing chimps.
Doctoral studies at the University of Tennessee led to a thesis on (surprise!) snakes. Krause explored the predatory habits of garter snakes on a Lake Michigan island that was thick with them. How, he wanted to know, do snakes find their earthworms and frogs, their salamanders and newts? How, too, does variation in diet affect a garter snake’s behavior, body weight, and head size?
“I’ve always been interested in the predator side of the equation,” he says. “We know that snakes use chemical clues to find their prey. But then you might find that a rough-skinned newt has evolved a chemical that will make the snake sick. The snake may then evolve resistance to that prey’s toxicity. Nature is an arms race.”
This is psychology?
This is evolutionary biology. This is organic chemistry. A good new–fashioned naturalist, Krause works the estuarial mix between psychology and the life sciences. As the stream of human knowledge advances, the more blurred become distinctions between the behavioral and the natural sciences. Krause studies learning. How does nature facilitate or constrain the learning process? Sensory perception and communication — whether in animals or in people — are critical components of learning.
“Much of what we know about learning,” he says, “comes from non-human species, from captured or domesticated animals. Mice, lab rats, pigeons. Pavlov’s dog. I’m trained as an experimental psychologist, but I study learning in wild. That’s where the psychology comes in. We take for granted that learning promotes survival, but we don’t know much about how.”
In a two-year post-doctoral stint at the University of Texas, Krause focused on sexual behavior in Japanese quail. He taught, at the same time, at nearby Southwestern University. That’s where he ran into Jesse Purdy, an experienced marine-mammal behaviorist. Purdy, too, was into psychology in the wild. He and Krause decided to pick something to study together. They would pool their resources and apply what they know to real-world interactions with marine mammals. Whales.
On the Alaska trip, in May, recording whale sounds was the easy part. “We got this catalogue of vocalizations pretty quickly,” Krause says. The hard part — part two — was to find an ideal site to broadcast the vocalizations. Because Krause is interested in the salmon’s response to sound alone, he must separate the sounds from live whales in the vicinity. In real life, of course, predatory signals would mean the whale is close by. Salmon could be responding not the sounds but to visual, or other, cues.
“You’d want a thick population of salmon in a bay or a cove. Shallow water. Clear, so you can video or sonar-record the salmon’s response. We found such a site near Cordova. Flew there from Anchorage, to an otter research facility. At this point we were just getting the methodology down. With our GPS [Global Positioning System], we established the exact coordinates for test sites.”
Testing the playback, Krause and Purdy dropped an underwater speaker by cable from a boat and played the orca sounds. Lacking big expensive equipment for now, they used a nice new fish-finder to begin watching what the salmon would do. Experimental control in a natural setting is complex. It’s not going to be sunny every May Krause returns to the test site. Late May is a good time of year for salmon to be there, but you never know about salmon. Mid-July, near Cordova, might be ideal.
“If salmon do react to sound alone, how much do they hear? Are they responding to the whistles? To the clicks? How is this different from their response to ambient boat sounds? To no sound at all? That’s what we’re trying to get at.
Krause is focused on resident orcas, very different from the transient orcas who also visit the Gulf of Alaska. Resident whales feed primarily on salmon. Transients prey on mammals – sea lions, otters, seals.
“Whales are smart,” he says. “Transient whales dive longer and are quieter than resident whales. Killer whales get blamed as murderous animals. It has been thought that transient whales are to blame for the decline in populations of sea lions. But maybe not. Probably not. Whales are smart, but prey are savvy, too. In mammalian prey, the sensory systems are evolved enough that they can register predators. We know that they do hear a wide range of sounds. Seals and otters, sensing the presence of a transient whale, make a mad dash toward shore. One terrified seal, sensing the approach of a transient orca, jumped onto a research boat. They say the seal perched on board for an hour.
“If it’s a resident whale nearby, seals are less likely to panic.”
So. Mammals, as prey, are good at social learning. Adult mammals stay with their young for a good long while. Natural selection favors seals who teach their young the “Yikes!” response. Hear that, pups? Head for shore!
Salmon, on the other hand, get no parental guidance. Salmon never know their parents. The evolutionary strategy of an adult female chinook is to lay 5,000 eggs and die, having invested all of her energy on the chance that a half dozen or so of her progeny will rise from the gravel and make it all the way out to sea and back to spawn.
“Salmon have a tough time, all right. But like honey bees and fruit flies, salmon do learn. It’s not social learning, but they can be conditioned. They learn by consequences. Herring, for example, change the shape of their school in the presence of a predator. We also know — from Jesse Purdy’s earlier work — that individual hatchery salmon show a startle–response to predator signals. It’s a subtle response. A slight increase in swim speed and heart rate. Now we’ll be looking at gross behavioral responses. Whole schools of salmon. Will the salmon scatter or bunch? Will they flee, or approach and investigate? We think of salmon as less astute than mammal prey. But is there anything salmon have evolved to defend against orca attacks? Nobody knows.”
Krause, among the cleverest of mammals, hopes to know. If this project works, he will find out. After two or three more summer trips to the Cordova field site, he will find out and will write it up. This is social learning. Human beings, the talking animals, will teach others of their species. What Krause finds in the wild will guide the development of his own laboratory here on The Bluff.
Mark Krause is still talking, but his listener’s attention leaps to the larger enigma, to the ingenuity of nature, to the marvel that over hundreds of millions of years a Devonian fish managed to end up as a two-legged researcher with an MP3 player, probing the secrets of fish.
Robin Cody is the author of the novel Ricochet River (now a really awful film) and an account of his Columbia River canoe trip from source to mouth, Voyage of a Summer Sun, which won an Oregon Book Award.
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