For years, researchers have been able to track where wolves roam using GPS technology—but that's about it. Without direct observation, scientists have had no way of knowing exactly what these elusive predators are up to in the wild, and what the metabolic cost of different behaviors might be.
That has begun to change, however. A team of scientists at UC Santa Cruz has now outfitted wild wolves with a new kind of high-tech collars. Using the same kinds of accelerometers found in smartphones and fitness trackers, these devices tell the scientists not only where the animals are, but also whether they're burning up calories by running or conserving energy while resting, and when. Essentially, the wolves are keeping a diary.
“The caloric budget of an animal is sort of its life blood" says Chris Wilmers, an ecology professor at UC Santa Cruz and co-investigator on the project. "If an animal burns more calories than it’s taking in, it’s going to die,” And with too few calories, the animal also can’t reproduce. “We are able to say how many calories the animal burned minute by minute, as its moving across the landscape, carrying out all the functions it needs to do, to live and survive.”
It's not just wolves: Scientists around the world are deploying these accelerometers on fish, sharks, and whales to shed light on animal behavior. This is a hot new field, says Caleb Bryce, a doctoral student with Terrie Williams, also a co-investigator on the project. But Bryce is especially interested in the canine carnivores, which are in serious decline. Filling in the gaps of their ecology can help inform conservation efforts, says Bryce. So he wants to understand how prey and landscape features influence wolves' movements. “In order to figure out how much they need to eat to survive, we need to understand behaviors, and how those metabolic costs add up,” says Bryce.
Before the team could collect useful information from collared wolves, however, the scientists needed to calibrate the collars in the lab, seeing how calorie burn corresponds to different behaviors—an energetic “signature” for each activity. The problem: how do you get a wild wolf to come in for lab testing?
The answer is that it's very difficult—but you can work with a dog, and that's almost as good. Because dogs are the evolutionary descendants of wolves, the information collected from pooches wearing "Smart" collars serves as a useful proxy for wild wolves. Cue Kida, a fluffy 100 pound Alaskan malamute. Bryce recruited Kida and other dogs from scientists and graduate students at Long Marine Lab, in Santa Cruz, California.
The dogs ran in an enclosed chamber for about 10 minutes sporting the collar. Air from the chamber was siphoned to an oxygen analyzer. After each session of running, walking, or galloping, Bryce could measure the amount of oxygen depleted from the chamber. That let Bryce calculate the approximate calorie burn for different behaviors.
Kida is the longest running member (so to speak) of the study. “She loves having a job,” says Brandy Gale, who owns Kida along with her husband Henry Kaiser. Kaiser adopted Kida at just six months from a malamute rescue organization that finds homes for abandoned pets. Kida is now almost nine years old. “She knows exactly how to get to the lab, and walks through the building right to it,” she says.
The dogs are cute, but working with them was not easy, explains Bryce. It took several months to train dogs to run and walk on the noisy and unfamiliar treadmill. Some even pooped and peed on the device. “The mess was spread all over the belt while it was spinning. Yuck!” Years later, the soapy marks used to clean the tread are still present.
Though dogs were originally just models for wild wolves, Bryce found some unexpected results from the experiments. Not all dogs are the same, it turns out. Northern breeds were more efficient at running, he says: they can go longer distances while using fewer calories. Bryce and his team are exploring the reasons behind the northern breeds’ surprising efficiency.
“We assumed dogs’ metabolic rate was close to that of wolves, because at the time, there wasn’t any wolf metabolic rate published,” Bryce says. Assumptions are risky in science, however so the next step was to work with captive wolves. Eventually, the team tested collars on five captive wolves at a facility in Indiana. The wolves were even more skittish than the dogs. It took over 16 months for train them for the treadmill work.
Finally last March, he spent a month deploying the collars on wolves across Denali National Park and Preserve, Alaska. “It’s pretty breathtaking,” says Bryce. “They are truly the symbol of wilderness.” Bryce and his team chose to collar wolves in Denali because it has one of few well-studied wolf populations that is considered natural, says Bryce. This is because there are fewer human impacts on the wolves, such as hunters and roads, than a place like Yellowstone National Park.
The park is also huge—it spans more than six million acres—with vastly different prey species and landscape features from east to west. In the west, the land is relatively flat, and wolves eat salmon as a portion of their diet. To the east, wolves have huge mountains to cross, fewer salmon, and more large prey like sheep and moose. The team collared five males each from different packs spread across the park.
“The wolves have different things to run up and down, and different prey,” says Bryce. “We want to see if we can detect those differences.” The animals wore the collars for eight months, and Bryce will spend the next several months analyzing the data. The next step is comparing these data to other populations, including those in locations where wolves encounter more human impacts and degraded habitat.
Though Denali is remote, even these wolves face human threats, he says. During the course of the study, one of the males was shot when he wandered outside the park boundary. “I was pretty devastated,” Bryce says.
Large carnivores are important ecologically,” he says. “They actually help maintain healthy prey populations, unlike populations that are exploding out of control unchecked by predators.” Take the 1995 reintroduction of wolves to Yellowstone, he explained. Before the wolves were brought back, elk and deer ran rampant, munching down all the trees. But with new predators lurking, they had to move more and break into smaller herds. Aspen and willow seedlings had a chance to grow. More trees also meant more food for beavers, whose dams create ponds and habitat. The ripple effect continued and soon fish, small mammals, songbirds, and hawks returned in higher numbers. “It is a classic example of how bringing one focal apex predator back into an ecosystem can restore balance and set things back on the right track,” he says.
Members of the Wilmers and Williams labs are deploying this SMART technology on other large mammals, including polar bears, narwhals, and mountain lions. As for Kida, her days of running on treadmills have ended—but she still gets daily seaside hikes with Gale.