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ABSTRACT. We recorded observations of caribou (Rangifer tarandus), grizzly bear (Ursus arctos), Dall sheep (Ovis dalli) and moose (Alces alces) along the Denali National Park and Preserve road corridor during 1995-97. We compared these observations to similar data from previous studies to evaluate the effect of an increase in traffic on the number of animals sighted and their behavior. Between 1972 and 1997, annual visitation to Denali National Park increased from about 45 000 to 350 000, with attendant increases in traffic on the park road. The mean number of caribou, grizzly bear, and Dall sheep observed did not decline (p > 0.301) from 1973 to 1997. The number of moose observed declined by more than 50% (R 2 = 0.529, p < 0.001). The estimated population of moose also declined over the same period (R 2 = 0.374, p = 0.002). The distance from the park road at which caribou and grizzly bears were sighted did not change (p > 0.787), but fewer moose (p < 0.031) were observed within 100 m of the road and fewer sheep (p < 0.011) were observed between 400 and 500 m from the road. Adverse behavioral responses to traffic (e.g., running from vehicles) occurred in less than 1.3% of observations for each species. Increased traffic on the park road apparently has not caused significant changes in abundance, distribution, or behavior of caribou, grizzly bear, Dall sheep, and moose in the park road corridor.

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Protected natural areas are not free from noise, especially noise generated by traffic within park boundaries. Natural soundscapes are important for maintaining community structure, providing positive visitor experiences, and increasing visitor support for management actions that reduce impacts on natural resources. To test experimental quieting as a strategy to increase both wildlife habitat quality and visitor experience, we enforced decreased speed limits and presented educational signage to reduce sound levels along a road system in an alternating, on-off block design within Grand Teton National Park, Wyoming, USA. We continuously recorded background sound levels while conducting bird space use assessments and visitor-intercept surveys along the experimental corridor. Our mitigation approach lowered sound levels during sign-present weeks, yet there was no relationship between bird space use near roadways and traffic noise, perhaps due to the increased duration of noise exposure created by lower speed limits. There was, however, a relationship between visitor perception of birdsong diversity and background sound level. Critically, visitors preferred soundscape mitigation strategies limiting personal access in exchange for better experiences in natural soundscapes.

A growing body of evidence suggests that traffic noise negatively affects wildlife. Protected natural areas are not free from noise exposure, both external to and within park boundaries. Natural soundscapes are important in many aspects of animal life histories, for increasing positive visitor experiences, and for providing psychological ecosystem services. To examine the use of signs as an effective traffic noise mitigation strategy, we experimentally altered speed limits from 45 mph to 25 mph, with additional educational signage, along the Oxbow Bend traffic corridor in Grand Teton National Park, USA. We continuously recorded sound levels between alternating week-long blocks while conducting avian point counts at each station. We detected 2,217 individuals of 48 species across all stations throughout the study. To assess visitor experiences with the soundscapes and visitor attitudes towards sign use and management strategies, we conducted stated-choice intercept surveys along a park turnout within the experimental corridor. We administered 471 surveys at an 82% response rate. Future data will evaluate impacts of traffic noise on avian abundance and distributions, visitor attitudes towards mitigation strategies, and the potential coupling between human and natural systems via the soundscape.   Featured photo from Figure 2 in report.