A community science project called Darwin’s Ark (darwinsark.org) has gathered information from a diverse cohort of pet dogs who were enrolled to explore how genetics shapes complex behavioral traits.
Modern domestic dog breeds are only 160 years old and the result of selection for specific cosmetic traits.
From sociable labradors to aggressive pitbulls, when it comes to canine behaviour there are no end of stereotypes. But research suggests such traits may have less to do with breed than previously thought.
Modern dog breeds began to emerge in the Victorian era and are often physically distinct – for example, Great Danes are huge and chihuahuas tiny. But it has often been thought breed can predict behaviour, too.
Now researchers say there’s little sign that’s the case.
Dr Elinor Karlsson of the University of Massachusetts Umass Chan medical school, a co-author of the study, said research revealed a huge diversity of behaviours within each breed.
“Even if the average is different, you’ve still got a really good chance of getting a dog that doesn’t match what people say that breed is supposed to be,” she said.
Writing in the journal Science, the US researchers report how they analysed survey responses relating to the physical traits and behaviour of 18,385 pet dogs, almost half of which were purebred, with genetic data analysed for 2,155 of them.
Analysis of the survey results for purebred dogs suggested about 9% of behavioural variation was explained by breed.
“For the most part, we didn’t see strong differences in breeds, but there are some [behaviours] that are connected to breed more than others,” said Karlsson.
While no behaviour was exclusive to one breed, howling was more common among beagles, while pitbulls and retrievers were more “human sociable”, or comfortable with strangers.
There were also some differences based on dogs’ ancestral functions. For example, herding breeds were, among other traits, more biddable.
But there was a high degree of variability between individuals, meaning it is difficult to predict a dog’s behaviour based on its breed.
To explore whether genetics explained the associations, the team analysed the behaviour of mutts that had different levels of ancestry from particular breeds. The results reveal some traits have a stronger genetic component than others.
Labrador retriever ancestry was associated with mutts who had few qualms about getting wet, yet such ancestry appeared to have no link to human sociability.Advertisement
“We’d expect that if Labrador retrievers are genetically more human social, we should see that mutts with more Labrador retriever ancestry to be more human social,” said Karlsson.
While the team’s other analyses found human sociability is highly heritable, Karlsson noted the mutt results suggest the genetic variants involved do not appear to be more common in particular breeds. Instead, differences between breeds for this trait may be down to environmental influences, or even owners’ perceptions.
But not all behaviours were found to be heritable, including how easily a dog is provoked by a frightening trigger – a finding that suggests that how aggressive a dog is may have little to do with genetics.
The team says the study has implications for owners.
“They should pay much less attention to all the stories about what their dog’s breed ancestry says about their behaviour and personality, and pay attention to the dog sitting in front of them,” said Karlsson.
Daniel Mills, professor of veterinary behavioural medicine at the University of Lincoln, who was not involved in the work, said genetics can give insights into populations but often reveal far less about individuals.
Mills added that it was not surprising genetics played little role in canine aggression, and criticised breed-specific legislation.
“Potentially risky behaviours … are unlikely to be controlled by simple genetic mechanisms since animals have to make judgment calls based on the much wider environment and their developmental history,” he said.
The findings came as another study, published in Scientific Reports, revealed that different breeds have strikingly different life expectancies.
The analysis of 30,563 records of dog deaths in the UK, collected between 2016 and 2020, showed that while jack russell terriers have a life expectancy of 12.72 years at birth, flat-faced breeds tended to have shorter lives, with French bulldogs having a life expectancy at birth of just 4.53 years.
Researchers have now investigated how genetics align with breed characteristics. Dogs are a natural system for investigating the genetics of complex traits. Millions of pet dogs live in human homes, sharing our environment, and receive sophisticated medical care. Behavioral disorders are treated with human psychiatric drugs, achieving similar response rates, and genetic studies suggest shared etiology with some human psychiatric conditions.
The DNA of more than 2,000 purebred and mixed-breed dogs was sequenced and the data, coupled with owner surveys, were used to map genes associated with behavioral and physical traits.
Although many physical traits were associated with breeds, behavior was much more variable among individual dogs.
In general, physical trait heritability was a greater predictor of breed but was not necessarily a predictor of breed ancestry in mutts.
Among behavioral traits, biddability—how well dogs respond to human direction—was the most heritable by breed but varied significantly among individual dogs. Thus, dog breed is generally a poor predictor of individual behavior and should not be used to inform decisions relating to selection of a pet dog.
Dogs are a natural system for investigating the genetics of complex traits. Millions of pet dogs live in human homes, sharing our environment, and receive sophisticated medical care. Behavioral disorders are treated with human psychiatric drugs, achieving similar response rates, and genetic studies suggest shared etiology with some human psychiatric conditions.
Before the 1800s, dogs were probably primarily selected for functional roles such as hunting, guarding, and herding. Modern dog breeds are a recent invention defined by conformation to a physical ideal and purity of lineage.
Breeds are commonly ascribed temperaments and behavioral proclivities based on the purported function of the ancestral source population. By extension, the breed ancestry of individual dogs is assumed to be predictive of temperament and behavior. Through
Dogs are a natural system for investigating the genetics of complex traits. Millions of pet dogs live in human homes, sharing our environment, and receive sophisticated medical care. Behavioral disorders are treated with human psychiatric drugs, achieving similar response rates, and genetic studies suggest shared etiology with some human psychiatric conditions
Darwin’s Ark was created as an open data resource for collecting owner-reported phenotypes and genetic data and invited any dog owner to enrol their dog.
The researchers, led by Kathleen Morrill, with Bioinformatics and Integrative Biology, University of Massachusetts Chan Medical School, was looking at variations among the breeds.
“Our inclusive approach achieved the large samples needed to investigate complex traits,” said the researchers in the paper published in Science.
We surveyed owners of 18,385 dogs (49% purebred) and sequenced the DNA of 2155 dogs. Most behavioral traits are heritable [heritability (h2) > 25%], but behavior only subtly differentiates breeds. Breed offers little predictive value for individuals, explaining just 9% of variation in behavior. For more heritable, more breed-differentiated traits, like biddability (responsiveness to direction and commands), knowing breed ancestry can make behavioral predictions somewhat more accurate (see the figure). For less heritable, less breed-differentiated traits, like agonistic threshold (how easily a dog is provoked by frightening or uncomfortable stimuli), breed is almost uninformative.We used dogs of mixed breed ancestry to test the genetic effect of breed ancestry on behavior and compared that to survey responses from purebred dog owners. For some traits, like biddability and border collie ancestry, we confirm a genetic effect of breed that aligns with survey responses. For others, like human sociability and Labrador retriever ancestry, we found no significant effect.