Clever as a Fox

Wednesday, March 25th, 2009

In Clever as a Fox, Geoffrey Milburn asks, What do all these domestic animals have in common?

All of these domestic animals have large white patches in their coats — areas where they’ve lost normal pigmentation — which is extremely common in domestic animals and not at all common in wild animals. Floppy ears are similar.

The Russian farm fox experiment demonstrated how piebald coats and floppy ears come along with domestication:

[Dmitri Belyaev] lost his job as head of the Department of Fur Animal Breeding at the Central Research Laboratory of Fur Breeding in Moscow in 1948 because he was committed to the theories of classical genetics rather than the very fashionable (and totally wrong) theories of Lysenkoism.

So instead, he started breeding foxes. Well, it was technically an experiment to study animal physiology, but that was more of a ruse to get his Lysenkoism-loving bosses off his back while he could study genetics and his theories of selecting for behavior.

He started out with 130 silver foxes. Like foxes in the wild, their ears are erect, the tail is low slung, and the fur is silver-black with a white tip on the tail. Tameness was selected for rigorously — only about 5% of males and 20% of females were allowed to breed each generation.

At first, all foxes bred were classified as Class III foxes. They are tamer than the calmest farm-bred foxes, but flee from humans and will bite if stroked or handled.

The next generation of foxes were deemed Class II foxes. Class II foxes will allow humans to pet them and pick them up, but do not show any emotionally friendly response to people. If you are a cat owner, you would call the experiment a success at this point.

Later generations produced Class I foxes. They are eager to establish human contact, and will wag their tails and whine. Domesticated features were noted to occur with increasing frequency.

Forty years after the start of the experiment, 70 to 80 percent of the foxes are now Class IE — the “domesticated elite”. When raised with humans, they are affectionate devoted animals, capable of forming strong bonds with humans.

These “elite” foxes also exhibit domestic features such as depigmentation (1,646% increase in frequency), floppy ears (35% increase in frequency), short tails (6,900% increase in frequency), and other traits also seen frequently in domesticated animals.

Belyaevn passed away in 1985, but he was able to witness the early success of his hypothesis, that selecting for behaviour can cause cascading changes throughout the entire organism. For instance, the current explanation for the loss of pigment is that melanin (a compound that acts to color the coat of the animal) shares a common pathway with adrenaline (a compound that increases the “fight or flight” instinct of an animal). Reduction of adrenaline (by selecting for tame animals) inadvertently reduces melanin (causing the observed depigmentation effects).

Frankly, I’m astonished that Paris Hilton isn’t running around with a tame silver fox — yet.

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