Dogs May Be Stressing Wildlife More Than We Realize, 12-Year Study Reveals

New research shows that even leashed pets can have lasting effects on wild animals living in parks and natural areas.

Taking your dog for a hike has become one of the most popular ways to enjoy the outdoors. Whether it's a morning walk through a neighborhood park or a weekend adventure on a forest trail, millions of dogs accompany their owners into natural spaces every year. While these outings provide excellent exercise and enrichment for pets, new research suggests they may also be creating an unexpected source of stress for wildlife.

A 12-year study conducted by researchers from the University of Wisconsin–Eau Claire and the University of California, Davis, found that domestic dogs have a significant impact on California ground squirrels living in parks and human-dominated landscapes. The research, published in the Journal of Urban Ecology, offers one of the longest examinations to date of how wildlife responds to the combined presence of people and their pets.

The findings reveal an interesting contrast: while adult squirrels gradually became accustomed to humans, they remained highly stressed by domestic dogs. Young squirrels, meanwhile, showed elevated stress levels in areas with frequent human activity, suggesting that age plays an important role in how wildlife adapts to urban environments.

Dogs Trigger a Strong Fear Response

For prey animals like squirrels, survival depends on recognizing potential predators.

Although today's domestic dogs spend their evenings curled up on the couch, many wild animals still perceive them as predators. Their size, movement, scent, and behavior resemble those of coyotes, foxes, and wolves—animals that naturally hunt small mammals.

Researchers found that adult California ground squirrels consistently displayed stronger stress responses when dogs were present than when humans were nearby alone.

Interestingly, adult squirrels appeared to become less fearful of people in areas with frequent human activity. Scientists believe this may be because parks and urban green spaces often contain fewer natural predators, allowing squirrels to become accustomed to people over time.

Dogs, however, were a different story.

Even regular exposure did not eliminate the squirrels' heightened stress response, suggesting that domestic dogs continue to be viewed as a genuine threat.

Young Squirrels Face Different Challenges

Perhaps the study's most surprising discovery involved juvenile squirrels.

Instead of responding primarily to dogs, younger squirrels experienced higher stress hormone levels in areas with heavy human foot traffic.

Researchers believe developing animals may be particularly sensitive to disturbances while they are learning to navigate their environment.

Chronic stress during early life can influence growth, immune function, and behavior. While the study did not measure long-term health effects, the findings raise important questions about how increasing recreation in natural areas could influence wildlife populations over time.

Wildlife Can Recover

There was encouraging news as well.

Researchers found that squirrels living in quieter areas with fewer people and dogs had significantly lower stress levels.

This suggests that wildlife is remarkably resilient when suitable habitat remains available. Providing protected spaces where animals can forage, reproduce, and rest without frequent disturbance may help reduce chronic stress and improve overall ecosystem health.

The findings reinforce the importance of maintaining buffer zones and preserving areas where wildlife can thrive with minimal human interference.

Why This Matters for Veterinarians

Although the study focused on squirrels, the results have broader implications for veterinary medicine, wildlife rehabilitation, and conservation biology.

Stress affects nearly every body system.

Prolonged elevations in stress hormones can suppress immune function, reduce reproductive success, alter feeding behavior, and increase vulnerability to disease.

Wildlife veterinarians and rehabilitators frequently observe the effects of chronic stress in injured or displaced animals. Research like this helps explain how repeated human recreation—even when well intentioned—can influence animal health before an injury or illness ever occurs.

The findings also support the growing "One Health" concept, recognizing that human activities, domestic animals, wildlife, and environmental health are deeply interconnected.

What Pet Owners Can Do

The researchers emphasize that dogs do not need to be excluded from nature. Instead, responsible recreation can significantly reduce their impact.

Simple actions include:

• Keeping dogs on designated trails.

• Using a leash where required.

• Preventing dogs from chasing wildlife.

• Respecting seasonal closures during breeding periods.

• Giving wild animals plenty of space.

• Avoiding areas specifically designated as sensitive wildlife habitat.

These small changes allow both pets and wildlife to safely enjoy shared landscapes.

A Growing Field of Research

This latest study builds upon previous work examining how urbanization changes wildlife behavior.

As cities expand and outdoor recreation becomes increasingly popular, scientists are discovering that animals adapt to humans in surprisingly complex ways. Some species become bolder, while others experience chronic physiological stress that may not be visible to casual observers.

Long-term studies like this one are particularly valuable because they capture changes that unfold over many years rather than a single season.

By following squirrel populations for more than a decade, researchers were able to identify patterns that shorter studies might have missed.

Looking Ahead

For veterinarians, conservationists, and pet owners alike, the message is clear: our presence in natural spaces matters.

Dogs enrich our lives in countless ways, but they also influence the ecosystems we visit. Understanding those impacts allows people to make small adjustments that can have meaningful benefits for wildlife.

As more families head outdoors this summer, the research serves as a timely reminder that responsible pet ownership extends beyond protecting our own companions—it also includes protecting the wild animals that share our parks, forests, and open spaces.

With thoughtful management, conservation planning, and public education, it's possible for people, pets, and wildlife to coexist while preserving the health of natural ecosystems for generations to come.

Source: University of Wisconsin–Eau Claire and UC Davis. Study published in the Journal of Urban Ecology.