Dog breeds tend to have signature traits: Border collies love to herd, greyhounds love to chase, and German shepherds make good guard dogs.

There’s a reason for that: Traits like these are highly heritable, according to a study of 101 dog breeds that identifies genetic differences in behavior.

The , published Oct. 2 in the Proceedings of the Royal Society B, points to 131 genetic variants, and offers new evidence to support what scientists have long suspected: that some of the behaviors that help characterize breeds — a drive to chase, for example, or aggression toward strangers — are associated with distinct genetic differences among them.

“Dogs present a good model for understanding what portion of the variation in their behavior is attributable to differences in genetics, and how much to their environment and experiences,” said , an assistant professor of psychology at the 91̽�� and a co-author of the study.

Most dog breed diversity has arisen in the last few centuries. People have bred dogs for their looks, but the bulk of breeding efforts have taken aim at eliciting particular behaviors, said James A. Serpell, a professor at the University of Pennsylvania’s School of Veterinary Medicine.

“If you look at the evolution of the dog, selection has been primarily for behaviors: hunting behaviors, guarding behaviors, or giving companionship to humans,” said Serpell, the study’s senior author.

What seems obvious — that genes can influence an individual’s behaviors — has not always been easy to support with evidence, in large part because behaviors are complex traits, the researchers said.Tendencies such as aggression, anxiety, or a compulsion to chase anything that moves are governed by many genes, not just one.

But dog breeds, being highly inbred, have allowed researchers to make progress in this area. Snyder-Mackler and the research team recognized that, if a dog breed is associated with a particular behavior that distinguishes it from other breeds, it might be easier to detect the genetic variants contributing to that behavior if that breed’s genome was compared to a host of others.

The team used data from C-BARQ, short for Canine Behavioral Assessment and Research Questionnaire, a survey that more than 50,000 dog owners have filled out about their pets. C-BARQ returned a result on 14 behavioral “factors” about each dog surveyed, giving a measure of traits such as stranger-directed aggression, excitability, energy level, and predatory chasing drive.

For this study, the researchers pulled 14,020 of those entries that included information about purebred dogs. To look for associations with genetics, they borrowed data from two earlier studies, together representing 5,697 dogs, for which 172,000 points in the genome had been sequenced.

They found that about half of the variation in the 14 measured behaviors across breeds could be attributed to genetics — a greater proportion than previous studies have found.

The traits with the highest rates of heritability — in other words, those that seemed to be most influenced by genetic factors rather than environmental ones — were behaviors such as trainability, predatory chasing, stranger-directed aggression and attention seeking. For these traits, genetics explained 60 to 70 percent of variation across breeds.

“These are exactly the types of traits that have been selected for in particular breeds of dogs,” said Serpell. “So for trainability, you’re thinking of breeds like border collies that have to respond to human signals to accomplish complicated tasks; for chasing behavior you can think of something like a greyhound, which is innately predisposed to chase anything that runs; and for stranger-directed aggression you might focus on some of the guard dog breeds that are highly protective and tend to respond in a hostile way to unfamiliar people.”

When the researchers looked for genetic variants associated with breed differences in the 14 C-BARQ traits, they found 131 variants tightly linked to these behaviors. Some were located in genes that have been implicated in influencing behavior, including in humans. But many were unknown and provide fodder for future study.

“This gives us an encouraging start and places to look,” said lead author Evan MacLean of the University of Arizona. “We have ongoing projects where we’ve obtained genetic and behavioral data from the same individuals, so we’ll be able to dive deeper into some of these traits and variants to see if the patterns we found here hold up.”

As a final step, the team looked to see where the genes in which key variants appeared were expressed in the body. Their analysis showed the genes were much more likely to be expressed in the brain than in other tissues.

The researchers’ results also leave plenty of room for individual differences and an animal’s environment in influencing behavior.

“It’s important to keep in mind that we looked at breed averages for behavior,” Snyder-Mackler said. “We’re not at a point yet where we can look at an individual’s genome and predict behavior. Environment and training still has a very, very strong effect.”

Bridgett vonHoldt of Princeton University was a co-author. The study was supported with a grant to Snyder-Mackler from the National Institute on Aging.

For more information, contact Snyder-Mackler at nsmack@uw.edu.

Adapted from a University of Pennsylvania news release.

Research in recent years has linked a person’s physical or social environment to their well-being. Stress wears down the body and compromises the immune system, leaving a person more vulnerable to illnesses and other conditions. Various stressors, from family adversity to air pollution, can lead to .

But scientists do not fully understand how the association between stress and health plays out at the cellular level. A new study examines one key stress-inducing circumstance — the effects of social hierarchy — and how cells respond to the hormones that are released in response to that stress. They found that social status determined how individual macaques responded to a key stress hormone, glucocorticoid.

“The goal is to understand the mechanisms through which social experiences or environment ‘get under the skin,’ so to speak, to affect health and survival,” said the study’s lead author, , a 91̽�� assistant professor of psychology.

The study, conducted in collaboration with researchers at Duke University, the University of Montreal and the Yerkes National Primate Research Center, is published Dec. 11 in the .

For this research, Snyder-Mackler and the team turned to a nonhuman social primate: . Scientists mixed up existing social groupings of nearly four dozen macaques, observed behaviors among the new groups, and analyzed blood samples to determine the cellular effects of the new social order. The team specifically measured effects on the peripheral immune system, which are immune cells that patrol other systems of the body, such as muscles.

Macaques were a suitable subject for this research, Snyder-Mackler explained, because they are relatively close cousins of humans but lack certain cultural or societal factors, such as substance use or access to medical care, which can complicate any corresponding study of human health.

The new study extends Snyder-Mackler’s research from his postdoctoral work at Duke University, which in a 2016 reported that social status had a direct effect on immune systems. The current study altered the groupings of monkeys to see how cells responded to what would happen in a short-term stress situation.

, social status has been linked to health and quality of life. Lower social status can mean less social and community support, and fewer buffers against stress or adverse circumstances. In animals, that equates to fewer allies and greater harassment from peers, while in humans, lower status is often tied to struggles with income, employment and relationship stability.

Organizing the macaques into nine new groups in effect created a new social hierarchy, the authors wrote, whereby the order in which each monkey was introduced also determined its status. The first in the group became the most dominant and held the highest rank, while the last to join the group typically held the lowest status.

After each group’s hierarchy was established and the team could observe the macaques’ behavior, the researchers then took blood samples and treated them with a synthetic glucocorticoid — which mimicked the macaques’ natural, primary stress hormone. In both macaques and people, glucocorticoid hormones are activated to mobilize resources during times of heightened stress; the ways that cells respond to a surge in stress hormones can indicate whether the body can appropriately respond to the stressor, or whether the stress pathway is chronically activated, which wears down the body and leaves it more susceptible to illness.

By using the synthetic-treated blood samples to simulate what happens inside the macaques during acute stress, the researchers could show how the glucocorticoid hormone could affect cellular behavior in different macaques — particularly whether macaques responded productively to the stress hormone, or had been worn down by it and no longer responded appropriately. In this experiment, the cells of the lower-status macaques were less able than those of the higher-status animals to respond productively to the glucocorticoid. One explanation for this lack of a response was found within the macaque immune cells’ genetic information. By measuring chromatin accessibility — how the DNA is packaged in the cell — they found that low-status females had immune cells that were less accessible to the signal from the glucocorticoids.

In humans, stressful or traumatic situations such as losing a job, caring for a chronically ill child or grieving the death of a loved one — the physical toll, at the cellular level, of stress on the human body. Snyder-Mackler’s work suggests one possible mechanism, namely altered chromatin accessibility, that may underlie glucocorticoid resistance in low-status individuals.

“Given the shared biology and evolutionary history between monkeys and humans, these findings help us better understand how social status can affect humans,” Snyder-Mackler said.

Further research is needed, he added, to identify the magnitude of the effects of stress, as ignited by a change in social status, and what buffers might protect individuals from those impacts. Not all individuals respond similarly to the same stress; some are more resilient — or susceptible — to the same stressor.

“We know that social adversity early in life can have far-reaching effects that extend into adulthood. The questions are, when do these events have to occur, how severe do they have to be, and are they reversible or even preventable?” Snyder-Mackler said.

The study was funded by the National Institutes of Health, the National Science Foundation, the Canada Research Chairs Program and the Natural Sciences and Engineering Research Council. Other authors were of Centre Hospitalier Universitaire Sainte-Justine in Montreal; Jordan Kohn and of Emory University and the Yerkes National Primate Research Center; of Wayne State University; of the University of Chicago; and Tawni Voyles and of Duke University.

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For more information, contact Snyder-Mackler at nsmack@uw.edu.

Grant numbers: NIH: R01-GM102562, R01-AG057235, P51-OD011132, K99/R00-AG051764, T32-AG000139; NSF: SMA-1306134; Canada Research Chairs Program: 950-228993; NSERC RGPIN/435917-2013.

Researchers from the 91̽�� and seven other institutions are working together to restore a Puerto Rican research station and its nearby community following the damage wrought last week by Hurricane Maria.

The research station known as Monkey Island is located on Cayo Santiago, off the southeast coast of mainland Puerto Rico, and is home to more than 1,000 rhesus monkeys. A site of scientific research since the 1930s, Monkey Island is staffed year-round by dozens of residents of the nearest mainland town, Punta Santiago.

Hurricane Maria, a Category 4 storm, devastated Puerto Rico, which, nearly a week afterward, remains without power and, in most places, water. Its governor said Monday that the U.S. commonwealth is reaching a “humanitarian crisis.”

That’s why scientists say they’re for residents and to rebuild the freshwater supply for the monkeys on Cayo Santiago. Researchers have established two GoFundMe pages – one for the , one for the – the latter of which has raised more than $30,000 so far.

“Our primary effort is to help our staff and the community near Cayo, while also trying to ensure that the animals are provisioned,” said , an assistant professor of psychology at the UW. “The local staff have incredible resilience and, while still dealing with the fallout from the storm in their personal lives, have continued to focus on the animals they care for.”

The first priority is to assist the local population with short-term needs, such as water purification systems and solar-powered flashlights, Snyder-Mackler said. Then the relief effort can support longer-term needs for the community and the research station that is supported by the community.

The is an international collaboration of faculty in the fields of psychology, biological anthropology and neuroscience from the UW, New York University, the University of Buffalo, the University of Exeter, University of Michigan, University of Pennsylvania, University of Puerto Rico and Yale University. The site is considered unique: The monkeys roam free on a natural tropical island, but also are habituated to humans, allowing them access into their daily lives. This microcosm of monkey society has informed studies of how the animals think, how they choose friends and mates, and what genes might underlie their complex social behaviors.

Though staff haven’t been able to take a precise count of the monkey population since the storm, they have observed distinct groups of monkeys, said James Higham, an assistant professor of anthropology at NYU.

“The good news is that we know that all the different social groups on the island have been accounted for, which means that most of these resilient monkeys weathered this powerful storm,” Higham said.

But the situation for the monkeys on the island remains precarious. Much of the vegetation, and all but one of the cisterns that hold rainwater for drinking, were destroyed, Snyder-Mackler said. The immediate effort for the animals is focused on reconstructing the cisterns to take advantage of the next rains.

update: heavy infrastructural damage (things can be replaced). monkey groups are accounted for. Full census starts tomorrow.

— Noah Snyder-Mackler (@SMack_Lab)

Snyder-Mackler, who joined the 91̽��earlier this month, has conducted research on the island for four years. Originally scheduled to return in mid-October, Snyder-Mackler studies the monkeys to explore the role of social support in the aging process. His work, which is funded by the National Institute on Aging, examines whether a positive social environment can slow the decline in our immune systems that typically comes with age. “This is one of the only naturally ranging populations of monkeys in which we can objectively measure every aspect of their social environment and how the environment, in turn, affects their biology over the entire lifespan,” he said.

��Access to and on Cayo Santiago is limited. The island is normally reached by boat, but the storm wiped out the dock at Punta Santiago, and some of the damage has been surveyed by helicopter, Snyder-Mackler said. Punta Santiago is about 40 miles from Puerto Rico’s capital, San Juan, but fuel shortages have made travel difficult.

��“It’s hard to fathom how these small monkeys managed to weather such a powerful storm, but they are not out of the woods yet,” said Snyder-Mackler. “We need to mobilize our resources to rebuild the infrastructure on the island as well as that of the community that supports it. If we don’t, we are at risk of losing one of our most valuable scientific resources.”

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Portions of this release were adapted from a joint statement by the researchers.