“Meet at 3?”
“Yo, where you at?”
“Are you going to Jennifer’s party tonight?”
We humans live in an interconnected world, where linking up with friends on the go is just a short text, a Skype call or a SnapChat away. Yet animals still manage to locate each other without nifty apps and gadgets—sometimes after being separated for long stretches of time and distance. How?
In one of the only studies of its kind, researchers have begun to shed light on how cheetahs reunite in Botswana’s Ghanzi region. The researchers were tracking three majestic feline companions who split from each other for a month and wandered miles apart. Then, suddenly, the trio came back together at a random spot. As the researchers report today in the journal PLOS ONE, the most plausible explanation is that the cats—which frequently mark their territory with urine and tree scratches—followed their noses.
“The methods the cheetahs use to reunite are not the ones I expected, like staying in the same area or reuniting in a place they often frequent,” says lead author Tatjana Hubel, a research fellow in the Structure and Motion Lab at the Royal Veterinary College of the University of London. “And I’m sure they didn’t agree a month in advance on a point to meet up at.”
Hubel and her colleagues were initially trying to investigate cheetahs’ hunting strategies. First, they equipped three male cheetahs—likely brothers—with GPS collars. (Adult male cheetahs are sociable, forming groups of two to four that researchers call “coalitions” and are often composed of brothers.) The collars took readings once every hour if the animals were sedentary; once every five minutes if they were walking; and five times a second if they were running. They tracked the animals for six months across their 300-square mile home range.
When the data came back, Hubel and her colleagues were surprised to see just how much time the cheetahs had spent apart from each other, and just how far they had strayed during that time. Mostly, the three boys—who the researchers dubbed Legolas, Gimli and Aragorn—stayed within 300 feet of each other. But at one point, Aragorn broke away from his buddies, and then spent the next 31 days wandering on his own, miles away.
A day before the meet-up, the animals were still 9 miles apart. Then, Aragorn looped around the area a couple times—as if searching for his friends—and finally converged with the other two at a seemingly random spot. “Researchers always assumed cheetahs stay close together, and that they split up for just a day or two,” Hubel says. “This was a surprise.”
To figure out what was going on, she and her colleagues used the process of elimination. Cheetahs’ vocalizations are more chirpy and soft that roar-y and loud, so the researchers guessed they weren’t using oral signals to communicate over long distances. Using their keen eyesight to keep tabs on each other was also unlikely, given that the area is scrubby and lacking any vantage points, making it difficult to see very far or survey the surroundings. And the chance that the animals randomly happened upon each other, the researchers calculated, was only about 1 percent. That left smell as the most likely navigational cue.
Robyn Hetem, a conservation physiology researcher at the University of the Witwatersrand in South Africa, says the paper provides “novel insights” into cheetah reunions, thanks to the “incredibly sophisticated technology” that the team used to take “previously unfeasible” measurements. But she thinks that the explanation for how the animals managed to meet may involve more than just scent markings. “Having observed the reunion of a cheetah coalition within a much smaller area in Namibia, I would advocate a strong role for vocal communications in facilitating that reunion,” says Hetem, who was not involved in the research.
This is the first time such fine-scale spatial data have ever been collected on cheetahs, and one of the few studies examining how any species manages to meet up in random locations. Once exception is lions, which we know find each other using roars that can be heard up to 2.5 miles away. Wolves, likewise, use howls. Other animals come back to a den, nest or hive, or to the place where they were born, using methods ranging from counting their steps to utilizing the sun as a compass, or relying on the earth’s magnetic field.
But as Hubel points out, returning to a known place is very different than finding each other at a random spot at a random time.
It will take further studies to figure out whether the smell hypothesis is correct. And the current study is difficult to generalize to all cheetahs, Hubel says, because the work focuses on just a single example involving only three individuals. It could be an anomaly that the cheetahs split up for so long, or that they found each other when they did.
“I’m not yet convinced that chance reunion can be ruled out,” says Neil Jordan, a conservation biologist at the University of New South Wales in Australia, who was not involved in the study. “[The authors] don’t seem to consider that cheetahs, particularly those from the same coalition, are likely to make similar decisions as one another as they move around their range, even when separated, which would greatly increase the likelihood of encounters between the two cheetah subgroups.”
Hubel and her colleagues were hoping to do a follow-up study to sniff out some of the answers to these unknowns. But before they could get started, Legolas was shot and killed by a farmer. “It’s illegal to kill cheetahs, but a lot of farmers just don’t want them on their land, because they think cheetahs are killing their livestock,” Hubel says. With the loss of Legolas, most likely it will be up to other researchers to further investigate the findings.
Hubel needs to get back to her hunting behavior studies, and the new site where she will be working isn’t open to putting GPS collars on many cheetahs, as tourists don’t like seeing those gadgets in the field. Still, she’s hopeful someone will pursue her discovery. “This is a prime example of unexpectedly finding something really novel and exciting,” Hubel says. “It could be the beginning of more research by other labs into how animals interact.”