Outdoor recreation noise triggers fear response in wildlife

Although we often seek peace and quiet in the woods, a recent study led by the USDA Forest Service Rocky Mountain Research Station has revealed that our recreation noise follows us, disturbing wildlife. 

This noise triggers fear responses in animals, akin to escaping predators, raising concerns about whether these habitats offer real refuge when humans are present and highlighting the need to balance recreation and conservation.

“Providing outdoor recreational opportunities to people and protecting wildlife are dual goals of many land managers,” wrote the study authors.

“However, recreation is associated with negative effects on wildlife, ranging from increased stress hormones to shifts in habitat use to lowered reproductive success.”

Wildlife responses to recreation noise 

“Wildlife responses to recreation noise are often unobservable, and it was a fun research challenge,” said lead author Katherine Zeller, an expert in wildlife biology at the Rocky Mountain Research Station. 

“Our study is the first to quantify responses to human-produced recreation noise based on recreation type, group size, group vocalizations, and wildlife species. Information like this can help managers balance recreation opportunities with wildlife management, which is critical as outdoor recreation continues to grow in popularity.”

Mimicking recreation noise to study wildlife

The research was conducted in the Bridger-Teton National Forest, Wyoming. The scientists used an innovative method to isolate and study the effects of recreation noise on various mammal species. 

The team placed wildlife cameras and speakers on trails, playing different types of noise when animals approached and capturing their reactions. These noises mimicked activities such as hiking, mountain biking, and off-highway vehicle use, with variations in group size and vocal presence. 

This setup allowed scientists to observe immediate changes in animal behavior and wildlife presence in response to these noises. 

Key findings of the study

• Increased fleeing and vigilance: Wildlife were 3.1 to 4.7 times more likely to flee and showed vigilance behaviors for 2.2 to 3.0 times longer when exposed to recreation noise compared to natural sounds or silence.
• Reduced wildlife presence: The local wildlife abundance was 1.5 times lower in the week following exposure to recreation noise.
• Impact of group size and activity type: Larger groups, especially vocal hikers and mountain bikers, had a 6 to 8 times greater likelihood of causing wildlife to flee.
• Species sensitivity: Elk and black bears were most sensitive to recreation noise, fleeing most consistently, while large carnivores were least affected.

“Our findings highlight the need for thoughtful planning, with potential consideration of noise mitigation measures to minimize the impact on wildlife while still providing outdoor recreational opportunities for people,” said study co-author Mark Ditmer, an ecologist at the Rocky Mountain Research Station.

“Noise from recreation can carry far beyond a trail system, so understanding how noise alone can affect wildlife is important for management.”

Impacts of human noise on wildlife

Human noise has significant impacts on wildlife, disrupting their natural behaviors and habitats. This noise, often originating from urban development, transportation, and industrial activities, can interfere with animals’ communication, making it difficult for them to find mates, avoid predators, and care for their young. 

For instance, birds may sing louder and at higher pitches to be heard over the din, which can be energetically costly and less effective. 

Marine life, particularly species like whales and dolphins that rely on echolocation, can be severely affected by underwater noise pollution from ships and sonar, leading to disorientation, stress, and even strandings. 

Additionally, chronic noise exposure can alter wildlife behavior, causing animals to avoid noisy areas, which may result in the loss of critical habitats and food sources. 

These disturbances can also affect reproduction rates and increase mortality rates due to accidents or predation in unfamiliar territories. 

The overall biodiversity and health of ecosystems can be compromised as species struggle to adapt to the relentless presence of human-made noise.

The study is published in the journal Current Biology.

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