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Dogs of Bali—A Study

Evidence of environmental effects on behavior
By Karen B. London PhD, June 2018, Updated June 2021

The dogs who colonized the island of Bali before the end of the most recent glaciation differentiated into their own unique breed at least 3000 years ago. In ancient times, far fewer people visited Bali than other islands such as neighboring Java, which limited migration of new dogs to Bali. For most of the last 100 years, a strict program designed to control rabies meant that few new dogs came to the island. Though genetic studies have found too much diversity among Bali Street Dogs (or BSDs as they are also known) for them to be considered a truly isolated dog population, they are believed to have bred freely and roamed the island with limited outside gene flow for thousands of years. Additionally, unlike many dogs around the world, BSDs have not likely been actively selected for specific morphological or behavioral traits.

The dog population of Bali offers an opportunity to investigate the question of how the environment in which dogs live affects their behavior and personality. Specifically, researchers asked how the personality and behavior of free-ranging dogs differ from dogs who live as human companions. It’s a hard question to explore in most situations because free-ranging dogs and owned dogs are not from the same genetic pool. That means that any differences that turn up could be genetic, environmental, or some combination of the two. Recently, many people—especially expatriates—in Bali have adopted BSDs as household pets, which involves confining them to houses and small backyards. This presents an unusual situation in which it is possible compare dogs from the same genetic pool but who live in different environmental situations.

For this research, people filled out the 75-item “Dog Personality Questionnaire” about 75 dogs in Bali. Those dogs that are living as human companions were evaluated by their guardians, and free-ranging dogs were evaluated by caretakers. The caretakers in this study are all familiar with dogs, in part because they all work for organizations focused on dog welfare. The caretakers knew the dogs in the study individually because the dogs roam free near where they live or because they regularly visited the area where the dogs live in order to care for them. Dogs were observed in a variety of behavioral contexts, including feeding, sleeping, traveling, scavenging, playing, and otherwise interacting with other dogs.

Researchers found distinct differences in the behavior and personalities of free-ranging dogs compared to those dogs who live with humans. The free-ranging dogs were overall less active, less excitable, less aggressive to people and less likely to chase animals or humans than was the case for dogs living as human companions. The evidence that being adopted (which results in being confined and having less to do each day) has negative effects on behavior and expression of personality is clear for BSDs. It’s not possible to compare Bali Street Dogs directly to dogs with guardians in other areas of the world, but the suggestion that free-ranging dogs are receiving the stimulation that allows their best selves to shine through while dogs in homes may not be is worth considering.


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If the dogs who were taken in as household pets and confined were the ones who showed less reactive, excitable or aggressive behavior, that could have been explained by people choosing to welcome the best-behaved dogs into their homes. Since the effect was the opposite—negative impacts on the dogs’ behavior associated with being taken in by people and confined—it must be considered that the lifestyle of so many of our dogs around the world who live in homes without the independence that free-ranging dogs have may be in environments that make it hard for them to behave as we might like. Of course, it is also a possibility that the dogs in Bali who are free-ranging and prone to the negative behavior that was more prevalent in the pet population may have been removed from the free-ranging population. (That sort of behavior is risky and could lead to injuries and loss of life due to fights or being hit by cars.)

This study offers some intriguing insights into the way that a dog’s environment or lifestyle affects behavior and personality, but the results are preliminary. Future studies with larger sample sizes are warranted, but it is exciting that scientists took advantage of a population of dogs that is genetically homogenous with individuals living in very different situations to explore this issue.

photo by hint of plum/Flickr

Karen B. London, Ph.D. is a Certified Applied Animal Behaviorist and Certified Professional Dog Trainer who specializes in working with dogs with serious behavioral issues, including aggression. Karen writes the animal column for the Arizona Daily Sun and is an Adjunct Professor in the Department of Biological Sciences at Northern Arizona University. She is the author of six books about canine training and behavior, including her most recent, Treat Everyone Like a Dog: How a Dog Trainer’s World View Can Improve Your Life