These Animals Are Not Pets, Please Don't Be Conned by Cuteness

Written by Dr. Karen Shaw Becker

wild fox

Story at-a-glance -

  • A recent study reveals that a Russian experiment to breed foxes for either tameness or aggression has changed the animals’ DNA in surprising ways
  • Some of the genetic differences uncovered by the researchers are responsible for tame and aggressive behaviors
  • The tame foxes were created simply by breeding the foxes least fearful of humans with each other
  • “Domestication syndrome” describes a group of distinctive genetic traits seen in domesticated animals that include both physical features and behavior
  • Despite the popular interest in pet foxes, they don’t make good pets; in addition, wild animals shouldn’t be purchased or taken from the wild for ethical reasons

For 60 years, foxes at the Russian Institute of Cytology and Genetics have been used in a selective breeding program known as the Russian farm-fox experiment. The foxes have been bred for either tameness or aggression in a bid to recreate the process of domestication from wolves to modern dogs.

In a study published not long ago in the journal Nature Ecology & Evolution,1 scientists evaluated the genomes of the two groups and revealed that the experiment has changed the animals’ DNA in unexpected ways.

Genetic Differences Between Tame and Aggressive Foxes

The research team looked for genetic regions differentiating the tame, aggressive and conventional populations of foxes. The “conventional” foxes were farm-raised relatives of the tame and aggressive foxes that weren’t bred for any particular behavioral trait.

The researchers sequenced the genomes of 10 animals from each population, and then compared them to a full fox genome and each other. The three groups differed in over 100 genomic regions, and as it turns out, some of those regions are responsible for tame and aggressive behaviors.

The research team focused on one of the regions that differed between the tame and aggressive foxes and discovered the friendliest foxes had a version of the SorCS1 gene that neither the aggressive nor conventionally bred foxes possessed. In addition, a different version of that gene found in aggressive foxes was exceptionally uncommon in the other groups.

The SorCS1 gene is associated with autism and Alzheimer’s disease in humans, and in mice, it’s involved in synapse formation and neuronal signaling.2

The researchers also identified genes that may be responsible for the difference in stress responses between domesticated and wild animals when they encounter unfamiliar people or objects. In addition, they located another genomic region in the aggressive foxes associated with Williams-Beuren syndrome in humans, a genetic condition that can be characterized by extreme anxiety.

How a Tame Fox Population Is Created

Breeding the tame, least fearful foxes with each other resulted in animals that were eager to make connections with humans. In addition, those foxes inherited physical features associated with domestication, including curly tails, floppy ears and white spots.

All of the alterations associated with domestication were created by simply breeding foxes based on their response to the presence of humans. The handlers at the Russian Institute of Cytology and Genetics interact with the foxes in a very specific series of steps when they conduct videotaped behavioral assessments.

They stand near each enclosure for one minute, hold the door open for another minute, reach toward the fox for a third minute, then close the door and stand near the enclosure for one final minute. The tamest foxes continue to try to interact with the handlers during the final minute of the assessment.

The animals who show curiosity about humans and allow themselves to be touched are included in the tame population. Those who back away and show other signs of fear are considered aggressive.

Why Domesticated Animals Have Similar Features and Behaviors

“Domestication syndrome” is a term coined by Charles Darwin to describe his discovery that “… domesticated mammals possess a distinctive and unusual suite of heritable traits not seen in their wild progenitors.”3 Domestication is seen not only in mammals like dogs, rabbits, foxes, pigs, horses or sheep, but also in domesticated birds and even fish.

According to the authors of a 2014 study published in the journal Genetics,4 when certain species are domesticated with the goal of taming them, it leads to genetic changes that affect a group of embryonic stem cells called the neural crest.

Neural crest cells form near the spinal cord of early vertebrate embryos. As the embryo develops, the cells travel to other locations in the body and create different tissue types, including pigment cells, parts of the head (skull, jaws, teeth, ears) and the adrenal glands, which are responsible for the fight-or-flight response. Neural crest cells are also indirectly involved in the development of the brain.

These genetic changes may explain why domesticated animals have many similar features and behaviors, including depigmentation (e.g., white patches), smaller ears, teeth and cranial capacity, shorter muzzles, floppy ears, curly tails and docile behavior.

Lack of Fear of Humans in Tame Animals May Be the Result of Abnormal Adrenal Glands

According to Genetics study co-author Adam Wilkins, Ph.D., of Berlin’s Humboldt University:

“When humans bred these animals for tameness, they may have inadvertently selected those with mild neural crest deficits, resulting in smaller or slow-maturing adrenal glands. So, these animals were less fearful.”5

The neural crest abnormalities Wilkins speaks of could also lead to physical signs of tameness — and not all of them good. For example, floppy ears are an appealing feature on dogs and rabbits, but unfortunately, they’re actually the result of deformed ear cartilage.

Animals with ears flopped over and hanging alongside their faces presumably don’t hear as well as those with erect ears. Domesticated animals also appear to have smaller brains than their counterparts in the wild. The decreased size of the forebrain seen in most domestic animals could be indirectly related to neural crest changes.

“Animal domestication was a crucial step in the development of human civilizations,” says Wilkins. Without these animals, it’s hard to imagine that human societies would have thrived in the way they have.”

A Word About Pet Foxes

It’s important to understand that the foxes involved in the Russian farm-fox experiment were and are used for research purposes, and each of us has an opinion on whether animals should be used in this manner. 

A bigger issue is the keeping of “pet” foxes, which is unethical, in my opinion — and an all-around bad idea. Foxes don’t make good pets, because despite their cuddly dog-like appearance, they retain many wild behaviors most people find hard to tolerate, especially when their “pets” reach sexual maturity.

More importantly, the fox is a wild animal, and like all wild creatures, belongs in the wild. There’s a reason it's illegal to take animals from the wild. Fortunately, it’s also prohibitively expensive to bring a (presumably) domesticated fox into the U.S., and several states ban them as pets.

There are countless homeless pets — including exotics — in shelters and rescues all over the country. I don’t think purchasing or trapping wildlife to hold captive is an honorable alternative to adopting a real pet.