Domesticated silver fox

The domesticated silver fox (Vulpes vulpes forma amicus) is a special type of silver fox, a dark-colored version of the wild red fox. These foxes were created through a scientific experiment that studied 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. They only let the friendliest foxes breed. Over many generations, the foxes became tamer and 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. These domesticated silver foxes are still used to study animal behavior and genetics.

Initial beliefs and research

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

Belyayev believed the key to domestication was choosing animals that were tameable. He thought that by only breeding the tamest foxes, they might develop other traits of domestic animals. He picked the silver fox for his experiment because it is closely related to dogs and had never been domesticated before. He planned to breed for tamability over many generations.

Domestication

The fox was hard to domesticate because it would not breed in cages. Scientists like Belyayev tried to breed animals in captivity but had many problems.

Belyayev studied the domestication of the Arctic fox. He kept careful records to learn more about how animals become domesticated.

Experiment

Lyudmila Trut started an experiment with foxes in 1952. She picked the tamest foxes from fur farms and only let the friendliest ones have babies. The scientists did not train the foxes. Instead, they let nature decide by choosing only the tamest foxes to breed.

Each month, the foxes were tested to see how comfortable they were around humans. Scientists would try to pet and feed them to see how the foxes reacted. By the time the foxes were seven to eight months old, they got a score based on how friendly they were. Over time, more and more foxes became very friendly, even acting like dogs. This showed how choosing friendly traits could change the foxes over many generations.

Results

Scientists saw 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.

Significance

Scientists study these special foxes to learn more about how animals can become friendly. They found that the foxes bred to be friendlier could understand human signs, like puppies can, even if they did not know many humans before. This shows that being friendly helps animals learn to understand people.

These studies also help us think about how humans learned to live together better. By learning about the genes that make animals wild or tame, we can understand both animal and human behavior better. Scientists wonder why only some 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 kept working on the experiment. In 1999, she wrote about it in a magazine named American Scientist. By that time, after many years and thousands of foxes, they had a group of 100 foxes that were much tamer than wild foxes. Trut thought Belyayev would be happy with the results.

When the Soviet Union broke apart, it became difficult to find 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 kept studying how to make other animals like rats, mink, and river otters live with people. They also raised foxes that were very scared and mean to learn more about how animals act.

Researchers checked the genes of the foxes to see what helps them be gentle or wild. They saw that some genes worked differently in tame foxes than in wild foxes. This helps scientists understand how animals change when they live with people.

Status

In 2014, officials said there were about 2,000 foxes. By August 2016, the farm had 270 tame vixens and 70 tame dogs.

Some people thought letting people keep these foxes as pets would help protect them. One scientist tried to bring some foxes to the United States but could not. 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 talked about the results of the silver fox experiment. Elinor Karlsson from the University of Massachusetts Medical School thinks the foxes might not have been fully wild at first. She believes some traits thought to be from domestication may have already existed. Adam Wilkins from Humboldt University of Berlin says even small changes can cause many different effects in animals. Lee Alan Dugatkin [/w/2] says there isn’t strong proof the foxes were already partly domesticated. He notes that the foxes did develop new traits during the experiment.