Pet deer attacks man! Pet wolf mauls child! Hand-raised tiger savages owner! Whenever one of these headlines flashes by my radar, I can't help thinking, "Why would anyone want a wild animal as a pet?"
Drawn by the animals' beauty and the novelty and status of having something exotic, many of these owners fail to appreciate the fact that wild animals are genetically adapted to living in the wild, and domesticated animals are adapted to living with humans, making domesticated animals much more appropriate as human companions. These adaptations have been unequivocally demonstrated in a landmark study by Dmitri Belyaev and Lyudmila Trut at the Institute of Cytology and Genetics in Russia.
In this study spanning 40 years and involving more than 10,000 foxes, researchers re-created the process of domestication by taking undomesticated commercial farm foxes and selectively breeding them solely for tameness over many generations. In each generation, the researchers raised all of the pups the same way and at 7 to 8 months old, they scored them for tameness. In each generation, the ones that scored the highest were bred.
Changes were clearly cropping up within a handful of years. By the sixth generation of breeding for tameness, some foxes were eager to establish human contact. They whimpered to attract attention and sniffed and licked the experimenters the way dogs would. By the 20th generation, 35 percent were this tame. By the 30th to 35th generations, 70 to 80 percent of the population was docile, eager to please and unmistakably domesticated. When tested in group enclosures, they competed for attention by snarling fiercely at each other. Even ones that escaped for several days eventually returned on their own.
This level of tameness was brought about by a number of interesting developmental changes. First, this population of fox puppies developed an expanded window for forming social bonds. During the sensitive period for socialization, animals learn which objects and animals are safe.
Those objects and animals they don't contact extensively during this period tend to elicit a strong fear response down the road. So the default setting in animals is to be fearful of new things, which is why wild animals don't come walking out of the woods to greet us like in Disney's "Snow White."
When dogs and other domestic animals aren't exposed to humans and common everyday objects such as people and their cars, hats, and umbrellas, they act as fearful as wild animals. Having an expanded window for forming social bonds provides more time for humans to assimilate into a dog's life, to form bonds with dogs, and to expose dogs to the many odd objects associated with civilization. In the domesticated foxes, this window was nine weeks, compared with six in their unselected counterpart. This expansion was due primarily to a delay in development of the fear response that follows the sensitive period for socialization.
These changes in turn correlated with differences in hormonal and neurotransmitter levels. The delay in development of the fear response was linked to lower levels of corticosteroids, which are stress hormones. The levels rose later and remained at a lower level in the farm foxes, so that by the 30th generation, the levels were approximately one-fourth that of the wild animal.
Additionally, the adrenal glands, which produce corticosteroids, released fewer corticosteroids when these farm foxes were subjected to emotional stress. Serotonin, a neurotransmitter in the brain that inhibits aggressive behavior, was higher in the domesticated foxes than the wild ones. Overall, the selection for tameness resulted in a fox that was less aggressive and less reactive to stressful stimuli and that went through an expanded sensitive period for socialization.
So what are the implications for wild animals living in our homes? Well, first it means that many of these animals are harder to tame than their domesticated counterparts. For instance, studies at Wolf Park in Indiana, where wolves are bred in captivity, managed in naturalistic conditions and studied scientifically, reveal that even pups born from tame wolves and raised in captivity became extremely fearful of humans starting around 8 weeks of age. These puppies have to be hand-reared away from the pack well before 14 days of age.
Additionally, after puberty, these now-adult wolves become harder for all but the most skilled humans to predict because they have a heightened drive to be No. 1 and take any opportunity to topple those above them. This dictates that all interactions, including play, are chances to test for weaknesses and upon detection can lead to life-threatening fights. Consequently, at places like Wolf Park, even the most skilled handlers stay out of the pens when they are even slightly sick or injured.
And from the wild animal's point of view, with its overactive stress-hormone response, confinement does not bode well in terms of contentment. Wolves rip through couches in search of interesting smells and ravage walls and windows in order to escape for a better time outside. Erecting a chain-link fence is the only way wolf owners can cope.
Domestication has over thousands of years imparted a number of changes that have allowed dogs, cats and other domesticated animals to live with humans. We should take advantage of these changes by choosing domesticated animals as our companions and leaving wild animals in the wild.
To find out how much work goes into caring for one wild species, read this article on A Day in the Life of a Show Biz Elephant.
Have you ever had a wild animal as a pet?