How to Tame a Fox (and Build a Dog)

by Lee Alan Dugatkin

  For the most part, as with wild foxes, animals engage in less play as they mature. This was why the discovery that the tamer foxes were continuing to engage in object play as they grew up was important. Another youthful behavior was being extended into fox adulthood, as with the whimpering, hand licking, and general calmness. Lyudmila and Dmitri had more strong evidence for Dmitri’s destabilizing theory that when you radically change selection pressures by choosing the tamest animals, you shake up everything, and a whole suite of changes follow.

  IN THE TENTH GENERATION OF PUPS, born in 1969, two more striking physical changes occurred. One of them showed up in a precious little tame female pup. She had remarkable ears.

  In wild populations, in the control population, and thus far in the experimental population as well, the ears of a fox pup are floppy until it is about two weeks old, and then they straighten out. This pup’s ears, though, didn’t straighten then, and they still hadn’t straightened by the third week, and then the fourth, and fifth, and on and on. Her floppy ears made this little pup look almost exactly like a dog puppy. She was given the name Mechta, which translates to “dream.”

  Lyudmila knew Dmitri would be delighted by Mechta’s ears, and she wanted to surprise him and let him discover Mechta for himself. But he was extremely busy that spring and didn’t visit the farm until three months after Mechta’s birth. To Lyudmila’s delight, Mechta’s ears were still floppy. When Belyaev saw her he exclaimed, “And what kind of wonder is this?!” He began showing a slide of her at all of his talks, and Mechta became something of a celebrity in the world of Soviet animal studies. At one conference in Moscow, after he flashed a slide of Mechta, a former classmate of Lyudmila’s approached her and said, only half-jokingly, “So your boss is deceiving the audience showing us a dog pup, and portraying it as a fox!”5

  The other new trait to appear in the tenth generation showed up in one male pup. This youngster displayed a new kind of pie-bald coloration. While in the prior generation, patches of white and brown had appeared on the belly, tail, and paws of a few tame pups, with this pup, a small white star patch appeared smack dab in the middle of his forehead.6 This is another common feature of domesticated animals, seen especially in dogs, horses and cows. “We would joke,” Lyudmila fondly recalls, “that [now] that a star had lit, this will bring us success.”

  So many of both the behavioral and physical traits of domestication had now shown up in the foxes that it seemed clear the experiment was working. But in order to prove Dmitri’s theory of what was happening to the foxes, Lyudmila and he would have to find evidence that genetic changes were driving the process. They had no real doubt about this; in many cases the new traits had been transmitted from parents to offspring. But the science of genetics requires even stronger proof. So he and Lyudmila would need more.

  The leading method at the time for establishing a genetic link to the appearance of traits was pedigree analysis, which involves comparison of traits through many generations of parents and offspring. Some variation in behavior and morphology always occurs between individuals of a species. No two foxes ever look or behave exactly the same. To conclude that the changes they had documented were truly tied to genes, the pedigree analysis would need to show the characteristic patterns of inheritance of traits that had been worked out over many years of research.

  This sort of work was pioneered by the monk Gregor Mendel, who in the middle of the nineteenth century, tracked patterns of change in the colors of peas over many generations. Subsequent researchers had honed the methods of pedigree analysis to allow for considering a wide variety of traits. Lyudmila had drawn up family trees for all of the foxes, and her meticulous notes about all of their behaviors and physical traits allowed her to perform this analysis. It was arduous work, but she dug in, and the results were clear; much of the variance that they saw in the new traits in the tame foxes was the result of underlying genetic variance.7

  Another way to garner powerful supporting evidence would be to replicate the results of the fox experiment with another species. In 1969, Belyaev decided to launch such an experiment. For this he turned to a young man named Pavel Borodin, who was in his last year as a biology major at nearby Novosibirsk State University. Pavel was friendly with Dmitri’s son Nikolai, and when Dmitri saw him one day on a visit to the university, he asked what Pavel was doing as his senior year project. “He didn’t detect any enthusiasm in my response,” Pavel recalls, “and then Belyaev said: ‘I’m not going to try to lure you away . . . you decide. But let’s take a trip to the fox farm and you can take a look at what we’re doing there.’” Borodin was excited at the prospect, and once he got there, he was hooked, amazed by how domesticated—and truly friendly—the foxes were.

  Belyaev wanted Pavel to follow the same basic procedure they followed with the foxes, but now with wild rats, and he wanted him to select and breed not only a line of rats that were calm and tame toward humans, but also an aggressive line. That would allow for important comparisons between their offspring over time. Pavel was given lab space at the Institute of Cytology and Genetics, but as for the initial population of rats, he would have to go out and catch them himself. “The main source of my animals,” Pavel recalls, “were the pig houses on farms. There were quite a lot of rats there. It was not easy to trap them because they were just clever animals, but anyway, I succeeded.” After a few weeks of trapping, he had brought a hundred rats back to the lab.

  Slightly modifying the technique that Lyudmila had developed for the work with foxes, Pavel would place a gloved hand into a cage and note whether a rat came over curiously to smell the hand or perhaps allowed him to touch it, or even pick it up. Some did. Others attacked, which was quite unnerving at first. But Pavel persevered, and after five generations, two dramatically different lines of rats developed, one increasingly tame, allowing him to pick them up and even pet them, and the other fiercely aggressive. Though Pavel moved on to other work thereafter, Belyaev decided to continue the experiment and hoped it would go on to produce more supporting evidence, which it has.8

  Another important step in producing definitive genetic results was to begin also breeding a line of aggressive foxes. As it had with the rats, reversing the procedure that had been followed with the tame foxes and selecting them for aggressiveness toward humans should produce an increasingly aggressive group of animals, which would allow them to begin making rigorous comparisons between the three populations—the tame, the control, and the aggressive. The work breeding the aggressive line got underway in 1970.

  While the elite foxes were a joy to work with, interacting with the aggressive foxes was not something the caretakers relished. The most aggressive were truly menacing, and they often lunged at Lyudmila with bared teeth when she tested them for selection. Those teeth are very sharp, and when foxes bite they bite hard. Most of the workers and scientists who helped Lyudmila with the foxes were terrified of these animals. “I looked at one aggressive fox,” recalled one of them about a particularly upsetting encounter, “and she gazed straight into my eyes but didn’t move . . . her fox eyes intently followed my every movement . . . I slowly brought my palm nearer to front side of the cage . . . and she reacted immediately. She threw herself to front side of the cage . . . her front paws against wire mesh . . . She had a really dreadful look: her mouth was open wide, ears were pressed tight to head and blind fury burnt in protruding eyes . . . When I looked into her eyes, I felt fear. My heart pounded rapid and blood rushed toward my head . . . I believed that she would have sunken her teeth into my face or neck if there were not wire mesh.”9

  Thankfully, one of the workers, a petite young woman named Svetlana Velker, was willing to take on the job. She was “a young, seemingly fragile woman,” as Lyudmila tells it: “everyone was afraid to work with aggressive foxes, [but] Svetlana was astonishing everyone with her courage.” Svetlana decided to just lay it on the line with the aggressive foxes. Tell them how it was going to work. “When she needed to handle . . .
an aggressive fox,” Lyudmila continues, “Svetlana told the foxes ‘you are afraid of me, and I am afraid of you, but why do I, a human, have to be afraid of you, fox, more than you are afraid of me?’” Then she got down to business. “Belyaev always admired her bravery,” Lyudmila recalls, “and used to say that they should raise her salary for this kind of work with aggressive foxes.”

  Others who would follow in Svetlana’s footsteps had their own special ways of dealing with the aggressive foxes. Rather than the stern disciplinarian approach Svetlana adopted, Natasha, who works with these nasty foxes to this day, decided that these animals were what they were by no fault of their own. They needed to be loved just as much as the tame foxes. And that is what she did and continues to do. “I like my aggressive foxes most of all,” Natasha says. “They are my children. I like the domesticated foxes, but I love aggressive foxes.”10 Whenever Lyudmila hears Natasha express this love, she laughs: “it is very, very rare” is all she can say. The courage of these assistants was to prove immensely valuable as the experiment progressed and the aggressive foxes allowed for important comparisons with the tame foxes.

  In the meantime Lyudmila and Dmitri got started on an important comparison between the population of control foxes and the tame foxes. Belyaev had theorized that genetically linked changes in the production of hormones involved in the regulation of the reproductive cycle, temperament, and physical features were responsible for the appearance of many traits associated with domestication. In order to prove this part of his theory, they would have to measure levels of hormones in the tame foxes versus the control group. With the sophisticated equipment available at the Institute for doing this, Lyudmila could begin performing this analysis.

  She decided to start by measuring the stress hormone levels of pups, to see if the tame pups had lower levels after the period when foxes normally start to become more anxious and fearful, between two to four months of age. This required a delicate procedure of taking blood samples from all of the pups, and this would have to be performed as quickly as possible, within no more than five minutes. Otherwise the levels of hormones would likely be elevated due to stress caused by the procedure, distorting the results.

  Measuring hormone levels was a technical kind of work that Lyudmila had no experience with, so she sought the assistance of one of her colleagues at the Institute, Irena Oskina, who specialized in the work. But the problem was that Irena had never worked with foxes. So Lyudmila asked the caretakers, with whom the pups were so comfortable, to help her. They had to take samples at several stages of the pups’ development, beginning before they were two months old and were still living in pens with their mothers, up until they were adults. The workers came through brilliantly. They would slowly reach in to get pups, trying not to alarm the mothers, and it was a true testament to how tame the adult foxes had become that the mothers didn’t react viciously when they did so. When it came to the control foxes, again the workers rose to the occasion—the control fox mothers can be very vicious if they think their pups are in danger. Wearing the two-inch thick protective gloves that Lyudmila ordered for them, they managed with some practice to do the work with great efficiency.

  When Lyudmila received the results of the analysis of the samples from Irena, she was delighted by the stark contrast in stress hormone levels. As expected, the levels rose in all of the foxes as they matured, but in the elite pups, the burst happened much later and the spike was much less pronounced, plateauing in adults at typically a 50% lower level than that of the control foxes. This was powerful confirmation of Dmitri’s destabilizing theory regarding changes in hormone production.

  AS BELYAEV BEGAN GIVING TALKS ABOUT all of these new results, the world scientific community became increasingly interested in the foxes. Dmitri was again allowed by the Soviet authorities to attend the International Conference of Genetics, which was held in Tokyo in 1968. His Japanese hosts were so taken with him and his talk that they presented him with some exotic domesticated roosters as a farewell gift. Somehow he got the live roosters on to the plane back to Novosibirsk.

  Dmitri also began submitting papers to international academic journals, and the first article to appear in English outside of the Soviet Union—entitled Domestication in Animals—came out in 1969. But, up to this point, scientific attention to the work was mostly limited to the genetics community; animal behavior researchers hadn’t taken much note of it. That changed when Belyaev received an invitation to the International Ethological Conference to be held in Edinburgh, Scotland, in September 1971. The conference was an invitation-only affair, bringing together the top researchers in the world. Dmitri was the first Russian scientist to be invited. The invitation came straight from the conference organizer, Aubrey Manning, who was one of the leading animal behaviorists in Britain. Manning had made it one of his missions to give a more international flavor to that year’s conference. He wanted to reach out beyond the usual crowd from Europe and the United States and give the meeting what he called “a kind of United Nations feel.”11

  Manning had heard about the fox experiment and found the work fascinating. He had conducted his own graduate research under the supervision of Tinbergen, and he was a specialist in studying the links between genes and behavior. He and his wife, the geneticist Margaret Bastock, had performed groundbreaking studies with fruit flies in the mid-1950s that were some of the first to link a gene specifically to a behavior in an animal. Manning thought the strong evidence for genetic causes of behavioral change that the fox experiment had produced were very important for the animal behavior community to learn more about. When he wrote to Belyaev before 1971 asking if he’d speak, Manning’s expectations were low. “This was at absolutely the height of the Cold War, of course, or at least the Cold War was pretty thick,” Aubrey recalls, “and contacts with the Soviet Union were slim.”12 When Belyaev replied with an enthusiastic “yes,” Manning was delighted that he had “extricated for the first time an ethologist from the USSR.”

  This was a big step for Dmitri and Lyudmila, and Lyudmila was excited about the opportunity to present their work to such an elite gathering. Manning asked Dmitri to bring a group of colleagues, and Lyudmila and a number of other researchers from the Institute were scheduled to attend. But shortly before they were due to leave, the government decided that only Dmitri would be allowed to travel. At least Lyudmila knew he would give a wonderful talk and their work would begin to make its way into the larger animal behavior discussion.

  The venue for the conference was the David Hume Tower at the University of Edinburgh. Each day Belyaev, Manning, and the other attendees heard a suite of thirty-minute talks by some of the most respected animal behaviorists of the day,13 including Tinbergen, who just two years later would be awarded his Nobel Prize as a cofounder of ethology. The sessions could be contentious, as there was a mini-battle going on in animal behavior between a European camp, who were primarily trained as biologists and tended to focus on genetics and study their animals in the field, and an American camp, who were primarily trained as psychologists and who focused on animal learning and worked with animals in the laboratory.14 Some researchers in the latter camp had taken the arguments about conditioning to such an extreme that they denied that any animal behavior could be genetically “programmed,” rather it was all the result of conditioning or learning. But a great deal of research by animal behaviorists out in the field was suggesting otherwise.

  Some of the most important of the observations were made by biologist E. O. Wilson, who had traveled the world observing colonies of insects of many types. In January of the year of the conference, his landmark book The Insect Societies was published. He vividly portrayed rituals in insect colonies and included stunning photos and drawings of leaf cutter ants tending their elaborate fungus gardens, fertilizing their food source with manure they have gathered, or marching along with leaves many times larger their own bodies hoisted over their heads; of army ants returning to their nest with the remains of their sco
rpion booty; and of wasps applying a concoction of ant repellent to their nests. He described how in the colonies of some ant species, workers serve as living honey pots to be tapped by the community in time of need. They store nectar and honeydew in their guts and hang upside down from rocks in the nest. When drought conditions hit, the others turn on these living spigots for shots of energy. He also described the frightening opposite side of ant behavior, vividly depicting their brutal tactics in warfare, as when three ants will hold another in place while an attacker cleaves its body in half.

  How could an animal like ants perform such purposeful feats, with such wide-ranging motivations? Much of it must be based on instinct.

  Yet the behaviorists had produced strong evidence of animal learning. American psychologist Edward Thorndike had tested how quickly cats and dogs could escape from “puzzle boxes” he had built. He observed that they initially tried all sorts of ways to get out, and then, when by chance they discovered a route, they readily learned to repeat the process, getting out of the box faster and faster. This, he argued, showed that animals learned their behaviors by being rewarded for them, whether that was a certain way to approach a bird they were about to pounce on or licking a hand that then rewarded them.

  Many animal behaviorists were beginning to think that it was quite possible that both genes and learning were involved in many of animals’ complicated social behaviors. It was not a one-or-the-other scenario—learning could be layered on top of genetic predispositions, and what’s more, the ability to learn may itself have an underlying genetic component. Belyaev thought this sounded about right.