Domesticated silver fox

The domesticated silver fox (Vulpes vulpes forma amicus) is a special type of silver fox, which is a dark-colored version of the wild red fox. These foxes were created through a scientific experiment that tested how animals can change when we carefully choose which ones get to have babies. This experiment took place at the Institute of Cytology and Genetics in Novosibirsk, Russia.

Scientists wanted to see if they could make foxes behave more like pets by only letting the friendliest foxes breed. Over many generations, the foxes not only became tamer but also started looking more like dogs, with some even developing spotted or mottled fur patterns.

This experiment was inspired by ideas about how wolves turned into dogs, as described long ago by Charles Darwin in his famous book On the Origin of Species. It showed how powerful selective breeding can be in changing both the behavior and appearance of animals. Even though some scientists later questioned some of the conclusions, these domesticated silver foxes remain an important tool for studying animal behavior and genetics.

Initial beliefs and research

Dmitry Belyayev wondered how different dog breeds came from their lupine ancestors. He thought the answer might lie in Mendelian inheritance. He noticed that many domesticated animals shared certain traits, like droopy ears or white patches in their fur. This idea is called the domestication syndrome.

Belyayev believed that the key to domestication was selecting animals for tameness. He thought that by choosing only the tamest foxes to breed, he could see if they would develop other traits typical of domestic animals. He chose the silver fox for his experiment because it is closely related to dogs and had never been domesticated before. His plan was to focus on breeding for tamability over many generations.

Domestication

The fox species was difficult to domesticate because it would not breed in cages. Scientists like Belyayev tried to breed animals in captivity but faced many challenges.

Belyayev focused on studying the domestication of the Arctic fox that had already been happening for many years. He carefully recorded the process to learn more about how animals become domesticated.

Experiment

Lyudmila Trut managed a special experiment with foxes starting in 1952. She collected the tamest foxes from fur farms and began breeding only the friendliest ones. The scientists did not train the foxes; instead, they let nature decide by only allowing the tamest foxes to have babies.

The foxes were tested each month to see how comfortable they were around humans. Scientists would try to pet and feed them to see their reactions. By the time the foxes were seven to eight months old, they received a score based on how friendly they were. Over time, more and more foxes became very friendly, even showing behaviors similar to dogs. This showed how selecting for friendly traits could change the foxes over many generations.

Results

Scientists noticed many changes in the foxes as they bred only the tamest ones over many generations. By the fourth generation, some foxes started wagging their tails like dogs. Their reproductive cycles also changed, and some females started having their mating periods earlier than usual.

Over time, the foxes developed other traits commonly seen in domestic animals, such as floppy ears, rolled tails, and multi-colored coats. They also had shorter skulls and tails, and their brains had higher levels of serotonin. These foxes became very tameable, eager to please, and clean, making them excellent pets. Some could even fetch and sit, showing just how much they had changed through selective breeding for tameness.

Significance

Scientists have studied these special foxes to learn more about how animals become tameable. They found that the foxes that were bred to be friendlier could also understand human signs just like puppies can, even though they did not know many humans before. This shows that being friendly might help animals learn to understand people.

These studies also help us think about how humans might have changed over time to live together better. By learning about the genes that make animals wild or tame, we can better understand both animal and human behavior. Scientists wonder why only a few animals, like horses, have been tamed by humans while others, like zebras, have not.

After Belyayev's death

After Belyayev died in 1985, scientist Lyudmila Trut continued the experiment. In 1999, she wrote about it in a magazine called American Scientist. By then, after many years and thousands of foxes, they had a group of 100 foxes that were much tamer than wild foxes. Trut believed Belyayev would be happy with how the experiment turned out.

When the Soviet Union collapsed, it became hard to get money for the research. Trut worked hard to keep the foxes safe. After Trut passed away in 2024, Anna Kukekova, a scientist at Cornell University, helped get funding from the National Institutes of Health to support the project.

Further research

Scientists continued to study how to domesticate other animals, such as rats, mink, and river otters. They also bred foxes that were very fearful and aggressive to learn more about animal behavior.

Researchers looked closely at the genes of the foxes to understand what makes them tame or aggressive. They found differences in how certain genes worked in domesticated foxes compared to wild ones. These studies help scientists learn about how animals change when they are domesticated.

Status

In 2014, officials said the number of foxes was stable at about 2,000. By August 2016, there were 270 tame vixens and 70 tame dogs on the farm.

Some people suggested letting people keep these foxes as pets to help protect them. One scientist tried to bring some foxes to the United States but was not successful. Two foxes were sent to the United States but were stopped at the border and sent to a zoo in Santa Ysabel, California. A sculpture honoring the scientist who started the experiment was built near the research institute.

Criticisms

Some scientists have debated the results of the silver fox experiment. Elinor Karlsson from the University of Massachusetts Medical School suggested that the foxes might not have been completely wild to start with and that some traits thought to be from domestication may have already existed. However, Adam Wilkins from Humboldt University of Berlin argues that even small changes during development can lead to many different effects in various species. Lee Alan Dugatkin [/w/2] points out that there isn’t strong evidence the foxes were already partly domesticated, and that they did develop new traits during the experiment.