Awww, cute foxes

And not-so-cute rats:

On an animal-breeding farm in Siberia are cages housing two colonies of rats. In one colony, the rats have been bred for tameness in the hope of mimicking the mysterious process by which Neolithic farmers first domesticated an animal still kept today. When a visitor enters the room where the tame rats are kept, they poke their snouts through the bars to be petted.

The other colony of rats has been bred from exactly the same stock, but for aggressiveness instead. These animals are ferocious. When a visitor appears, the rats hurl themselves screaming toward their bars.

"Imagine the most evil supervillain and the nicest, sweetest cartoon animal, and that’s what these two strains of rat are like...."

"The ferocious rats cannot be handled....They will not tolerate it. They go totally crazy if you try to pick them up."

Belyaev’s hypothesis was that all domesticated species had been selected for a single criterion: tameness. This quality, in his view, had dragged along with it most of the other features that distinguish domestic animals from their wild forebears, like droopy ears, patches of white in the fur and changes in skull shape.

[Dmitri K. Belyaev, who believed in Mendelian theory despite the domination of Soviet science by Trofim Lysenko] chose to test his theory on the silver fox, a variant of the common red fox, because it is a social animal and is related to the dog. Though fur farmers had kept silver foxes for about 50 years, the foxes remained quite wild. Belyaev began his experiment in 1959 with 130 farm-bred silver foxes, using their tolerance of human contact as the sole criterion for choosing the parents of the next generation...

In fact, after only eight generations, foxes that would tolerate human presence became common in Belyaev’s stock.... [A]fter 40 years of the experiment, and the breeding of 45,000 foxes, a group of animals had emerged that were as tame and as eager to please as a dog.

As Belyaev had predicted, other changes appeared along with the tameness, even though they had not been selected for. The tame silver foxes had begun to show white patches on their fur, floppy ears, rolled tails and smaller skulls.

The tame foxes, Dr. Fitch reported, were also "incredibly endearing." They were clean and quiet and made excellent house pets, though — being highly active — they preferred a house with a yard to an apartment. They did not like leashes, though they tolerated them...

[Dr. Brian Hare of the Planck Institute] found that the fox kits from Belyaev’s domesticated stock did just as well as puppies in picking up cues from people about hidden food, even though they had almost no previous experience with humans. The tame kits performed much better at this task than the wild kits did. When dogs were developed from wolves, selection against fear and aggression "may have been sufficient to produce the unusual ability of dogs to use human communicative gestures," Dr. Hare wrote last year in the journal Current Biology.

My Kaohsiung rats, incidentally, while not particularly endearing to me, at least, weren't hostile. Rather a little curious, but also a little shy.