In a number of other Psychology Today posts (here and here), I have written about the remarkable silver fox domestication study that my colleague and friend Lyudmila Trut (who has been leading this study since 1958; not a typo, she turns 85 next month) and I discuss in our book, How to Tame a Fox and Build a Dog. In those posts, I discussed how this six-decade (and counting) experiment has produced behaviorally tame foxes that look remarkably dog-like. Here, I want to tell you about one of the more remarkable traits that has recently appeared in these foxes.

This part of the story begins in the 1980s when Lyudmila heard some of the domesticated foxes vocalizing in an odd new way, making a high-pitched “haaaaaw, haaaaaw, haw, haw, haw” sound when people approached them. Lyudmila thought it sounded like they were and called it the “ha ha” vocalization. But neither Lyudmila nor the other researchers in the fox study had knowledge of how to study vocalizations, so not much came of the new sounds. Then, in 2005, Lyudmila got a phone call from Svetlana Gogoleva.

Gogoleva, a 20-year-old undergraduate student at Moscow State University, was working in the lab of Ilya Volodin, a professor who specialized in animal communication. She knew of the fox experiment and thought it presented a unique opportunity to study how domestication affected the evolution of animal communication abilities. She and Volodin contacted Lyudmila proposing that Gogoleva visit the experimental fox farm in Novosibirsk, Siberia and record all of the foxes’ vocalizations so that she could compare the domesticated foxes to a control line of foxes that had not been selected based on their behavior to humans, and an aggressive line of foxes that had been selected based on how antisocial they were to humans.

Gogoleva began her work at the experimental fox farm in the summer of 2005. She began by cataloging the different sounds made by the domesticated, aggressive, and control foxes. It was immediately clear that the aggressive foxes were louder than the other animals. But, Gogoleva wasn’t especially interested in volume: she wanted to understand the natures of the sounds, and see if there were differences between domesticated, control and aggressive animals, so she tested 25 females from each of the groups.

In each trial, in a precise, methodical, manner, and armed with a Marantz PM-222 tape recorder, Gogoleva approached a fox in its home pen. She would stand two to three feet in front of the pen, and if the fox started making sounds, she recorded them for about five minutes. After many months of work, she recorded 12,964 calls, and all of them fell into one of eight categories. Four types of sounds were made by foxes in all groups—domesticated, control, and aggressive—but of the other four sounds, two were made only by the domesticated foxes, and two only by either the aggressive or control foxes.

The two sounds made only by the aggressive foxes and some of the control foxes were vocalizations that sounded like a snort and a cough. But one of the vocalizations made only by the domesticated foxes, and by almost all of them, from a very young age, was a rapid-fire rhythm of cackle, pant, cackle, pant that produces the strange “ha ha” sound that Lyudmila knew so well. Gogeleva ran a detailed analysis of the nature of “ha ha” sound, considering factors such as duration, amplitude, and frequency. What she found was that the “ha ha” sounds mimicked the sound of human laughter very closely. Closer than any other nonhuman vocalization. When she looked at a spectrogram that allowed her to visualize the domesticated fox “ha ha” sound, and a spectrogram of human laughter, she was hard-pressed to tell the difference. The similarity was astonishing. Almost eerie. Of course, the domesticated foxes make their “ha ha” sound regardless of what we might consider funny. But that doesn’t change the fact that the domestication experiment has now produced foxes that not only act and look like a lapdog, but will give you a “ha ha” when you need a laugh, as well as when you do not.

Gogoleva and Lyudmila hypothesize that the tame foxes make the “ha ha” sound to attract human and prolong interaction with people. Somehow, they propose, the tame foxes have become adept at pleasing us by the sound of our own laughter. How, they don’t know, but a more pleasant way for one species to bond with another is hard to imagine.