It’s easy to forget that our beloved pets are descended from wild species that can still be found roaming the forests and hunting down prey. After all, they’re so friendly and lovable, and put up with our molestations with good humour. And many of them barely resemble their ancestors anymore, their appearance so greatly modified through selective breeding. So it sometimes comes as a bit of a surprise or even a shock to see them engaging in behaviour that we don’t typically associate with a housepet.
Since getting all this snow, Raven has been channeling her inner Wild, and on any given walk she’ll pause many times to investigate something she thinks she’s discovered under the snow. To try to get at the perceived critter, she rears back on her hind legs, then drives her front ones down onto the target spot. The extra force punches through the layers of crusty snow underneath, exposing the tunnel network that rodents would create close to the ground. She then buries her face in the snow, perhaps whuffling once or twice, as she tries to locate the mouse she just knows is under there. This can be repeated several, sometimes dozens of times, in a location. She never finds any animals, although I wouldn’t be surprised if she is actually smelling their scent in the tunnels they’ve made.
This is undoubtedly an instinctual behaviour, drawn from her ancient Wild DNA. My assumption is that it would be more logical for her to dig to try to expose what was underneath, the way she might dig into a burrow in the ground in the summer, and that the odds would be slim she’d develop it as a learned behaviour in the absence of a teacher. We as humans tend to be very detached from our instinctual Wild side, it being buried long ago with the increasing brain size and formation of civilization.
It’s an interesting form of genetic “memory”, behaviour. Phenotypic DNA sequences act more like a blueprint, telling the construction workers which types of bricks to use and where to lay them down, but behavioural DNA is much more subtle, and presumably codes for certain ways that the neurons all fit together. At what point does a learned behaviour cross the threshold to become an instinctual and inheritable behaviour? Do some behaviours happen by random neuron-crossing, and then when they turn out to be beneficial to the organism they end up getting passed down to the next generation? Undoubtedly someone somewhere has asked these questions, but they’re not the topic for today’s post, so looking up the answers will have to wait.
I wanted to talk about domestic dogs today. Back when binomial nomenclature was first introduced, Linnaeus classified domestic dogs as Canis familiaris, their own unique breed. Relatively recent research, in the early 1990s, examined the DNA of the various Canid species to determine hierarchical relationships between the different species. Results of the research showed that dogs share 99.8% of their DNA with the Gray Wolf, Canis lupus, but only 96% with the Coyote, Canis latrans. Two humans may share 99.9% of their DNA; humans share 98% with chimpanzees. (For a really interesting statistic, humans share 50% of their DNA with bananas.) The results strongly suggested that the domestic dog was not in fact a unique species, but simply a subspecies of the wild Gray Wolf, with a genetic predisposition to accepting humans as friends and a great deal of variation in their appearance, the way eastern Asians developed black hair and Europeans evolved blond, but we’re still the same species. This reclassification was adopted by the Smithsonian Institution and the American Society of Mammalogists in 1993, and the dog became Canis lupus familiaris.
There are two theories presented for how Canis lupus familiaris came to be. The first is that humans intentionally domesticated the dog, searching out and stealing puppies from their mothers and raising them in a human setting, and then selecting and breeding the most human-tolerant individuals. The second, and the one that seems to have greater popularity at the moment, is that as humans started forming more permanent settlements, and accumulating refuse at the edge of the community, wolves started to sneak in to scavenge from the waste piles. Wolves with a greater tolerance for a proximity to humans would be able to scavenge more food, and therefore would gain a greater fitness that in turn would help them win more mates and make more pups.
As they became tamer, the wolves would have been allowed to enter the camp and/or humans would have started approaching and interacting with the most tolerant individuals, much like we enjoy feeding chickadees seeds from our hands. Wolves that associated with humans would have benefited greatly over those who chose not to. Humans might have discovered they could get the tag-alongs to help bring down a wounded kill that might otherwise have gotten away from the hunter; as a reward for its effort, the wolf would have been given the innards when the animal was gutted. Around camp, the wolves might have been fed scraps that helped to keep the place cleaner. Over time, the tame wolf population became functionally separated by behaviour from the wild population, and the domestication of the dog had begun.
Using both archeological and DNA evidence, it’s estimated that dogs diverged from wolves around 15,000 years ago, although some estimates may put it as long ago as 40,000 years. By using the DNA of the world’s different breeds and “mapping” where each breed originated, it appears that the domestication of the dog occurred in eastern Asia, and presumably they traveled with humans to new areas from there. Domesticated dogs arrived in North America over the landbridge about 8000 BC (10,000 years ago), and gradually diverged into many breeds. Nearly all of these indigenous North American dog breeds are now gone, having died out with traditional practice of Native American culture, or, even before that, having been bred with or replaced by European dogs.
We would have to go back a long ways to find any trace of east-Asian wolf in Raven’s pedigree, but the behavioural instincts of her wild counterparts have been faithfully passed down from one generation to the next, across centuries. They cause her to punch holes in snow, chase deer across meadows, sniff other dogs’ bums and circle three times before lying down. (Okay, I’ve never actually seen her do the last one, but it’s a dog stereotype.) Her mama never had a chance to teach her these things, and we certainly haven’t, so they must be inherited. Although, I wonder what sort of bedtime stories Mama Dog tells her youngsters…
I couldn’t find a good Creative-Commons-licensed photo of a wolf or coyote exhibiting this behaviour, but here’s another canid, in an appropriately wintery scene:
Edit: Ken/Randomtruth of Nature Of A Man offered this great capture of a coyote mid-pounce. You can read about the encounter at his blog, here. Thanks, Ken!