How selective breeding has changed dog behavior
For centuries, humans have bred dogs for specific traits or behaviors, developing breeds with a wide range of “specializations,” from companionship to herding or scent hunting. A new study shows that this selectivity has led to distinct dog breeds with distinctive brains.
According to the American Kennel Club, there are more than 340 dog breeds around the world, each with distinctive traits and behaviors.
From prehistoric times to the present day, humans have bred dogs for fun and companionship, for their beauty and elegance, or to help with chores.
The original role of Alaskan malamutes and Siberian huskies, for example, was to pull sleds, while that of beagles and dachshunds was to stalk their prey.
Huskies and malamutes are double-layered, which allows them to regulate body temperature in subzero temperatures, and beagles and dachshunds have a keen sense of smell, which allows them to detect the distinctive smells of other animals.
While it is clear that the selection was aimed at selecting the traits best suited to particular environments or tasks, the selection focused not only on physiological and functional characteristics, but also on specific behaviors.
This made it possible, for example, for dogs bred for company to be adaptable and ready to make friends, and for others, originally bred for sentry work, to be much more on their guard.
So where do these differences in behavior – and functional traits, such as a keen sense of smell – come from?
A new study – first authored by Erin Hecht, assistant professor at Harvard University, Cambridge, MA – has found that behavioral differences specific to particular dog breeds correspond to variations in brain network structures between the races.
For the present study, the conclusions of which are presented in The Journal of Neuroscience – the researchers analyzed MRI scans of the brains of 62 purebred dogs belonging to 33 different breeds.
These breeds were: Basset Hound, Beagle, Bichon Frize, Border Collie, Boston Terrier, Boxer, Bulldog, Cavalier King Charles Spaniel, Cocker Spaniel, Dachshund, Doberman Pinscher, English Pointer, German Shorthair Pointer, Golden Retriever, Greyhound, Jack Russell Terrier, Keeshond, Labrador Retriever, Lhasa apso, Maltese, Miniature Schnauzer, Old English Sheepdog, Pit Bull, Siberian Husky, Silky Terrier, Springer Spaniel, Standard Poodle, Weimaraner, Welsh Corgi, West Highland White Terrier, wheat terrier, whippet and Yorkshire Terrier.
The researchers also classified these breeds into 10 groups, according to “behavioral specialization,” as given by the American Kennel Club. They were:
- scent hunting: basset hound, beagle, dachshund
- company: Bichon Frize, Boston Terrier, Bulldog, Cavalier King Charles Spaniel, Keeshond, Maltese, Yorkshire Terrier
- breeding: border collie, old english sheepdog, welsh corgi, wheat terrier
- pest control: Boston terrier, dachshund, Jack Russell terrier, miniature schnauzer, silky terrier, West Highland white terrier, Wheaten terrier, Yorkshire terrier
- sports fights: Boston terrier, boxer, bulldog, pit bull
- Sentinel work: boxer, doberman pinscher, keeshond, Lhasa apso, wheat terrier
- police work: boxer, Doberman pinscher
- bird recovery: cocker spaniel, english pointer, german shorthaired pointer, golden retriever, labrador retriever, springer spaniel, standard poodle
- sight hunting: greyhound, weimaraner, whippet
- war: boxer, doberman pinscher
The researchers deduced that the behavioral differences were directly related to the differences in brain anatomy because, they explain, if they weren’t, “the variation would have to be randomly distributed across [brain] Regions. “
Instead, as MRI scans indicated, there were differences in the same distinct brain networks between different species, suggesting they might correspond to differences in selected behaviors.
However, researchers first had to identify distinct, mostly independent brain regions in order to see if they differed between races.
They were able to identify six: one “relevant to the social bond with humans”, one supporting conscious responses to tastes and smells, one relevant to moving around the environment, one probably “involved in action and ‘interaction’, a region associated with affective processes. related to fear as well as mating and aggression, and one related to the processing of odors and visual stimuli.
âHaving identified these six networks, we then studied their relationship with the phylogenetic dog [evolutionary] tree â, explain the authors in their study document.
âWe have found that the majority of the changes that occur in these components take place in the terminal branches of the tree (ie individual races),â they continue. This means that, among races, differences in these networks corresponded to differences in behavior.
âIn the six regional covariant networks that we found, significant correlations were found with at least one behavioral specialization. Associations between brain networks and associated behavioral specializations are apparent, âthe authors write.
The researchers also offer a few examples, noting that breeds specializing in scent hunting have a better-developed network that supports conscious responses to scents.
In their conclusion, the investigators note:
“These results strongly suggest that humans altered the brains of different breeds of dogs in different ways through selective breeding. “