Listen Up, Hikers

What if nature-lovers inadvertently cause negative impacts to wildlife?

by Michelle Reilly

JHU alumni, MS Environmental Sciences & Policy, 2011

In June of 2011, I finished my Master’s degree at Johns Hopkins University, handed in my independent research project, and moved to Arizona. I was hired by Dr. Paul Beier as a PhD research assistant on a very important project: to investigate how habitat use is impacted by different levels of hiking and biking. Recreation is the second most widespread cause of species endangerment on federal land in the United States (Losos et al. 1995), and within the category of recreation, disturbance from hiking was second only to disturbance caused by off-road vehicle use (Losos et al. 1995).

Previous research shows that impacts to wildlife from non-motorized recreation result from two principle mechanisms. Hikers accompanied by dogs have the potential to greatly impact wildlife. First, domestic dogs directly impact wildlife through harassment—such as chasing—which results in disruption of normal maintenance routines of wildlife (Sime, CA. 1999). Second, recreationists and dogs indirectly affect wildlife through disturbance. Even minimal disturbance such as displacement from one area to another can cause avoidance of suitable habitat (Papouchis, 2001). That is, without giving chase, dogs can still elicit responses in wildlife and cause altered behaviors (Lenth, Knight, Brennan, 2008).

Image courtesy of Michelle Reilly, taken via Reconyx HC600 camera trap

Image courtesy of Michelle Reilly, taken via Reconyx HC600 camera trap

In short, hiking has the potential to seriously impact habitat used by wildlife through disruption of normal activities. Disruption of daily maintenance routines increases energy expenditures and lessens the amount of time wildlife can spend foraging. Avoidance of potentially suitable habitat further impacts wildlife populations. And the ways in which wildlife uses or has the ability to use an area influences the carrying capacity for that species.

Past research has investigated physiological impacts of recreation on individual animals but there is limited research on how recreation affects habitat use by a group of species. This is where my research comes in. I proposed to investigate how different levels of hiking and biking impact habitat used by a suite of species. Camera traps would be used to calculate habitat use for medium and large mammal species in the San Francisco Bay ecoregion. Camera traps are a reliable and noninvasive method for estimating habitat use by wildlife and can concurrently be used to track human recreation in an area. My research would use repeated presence-absence data to model habitat use by applying Bayesian hierarchical methods developed by Royle and Dorazio.

The research goals are these: 1) quantify how habitat use by mammals (rabbits and larger) is affected by the amount of hiking, mountain biking, equestrian use, and domestic dog activity in natural areas and 2) provide guidance managers can use to locate trails and manage non-motorized recreation is ways that do not degrade the habitat value of natural areas.

Image courtesy of Michelle Reilly

Image courtesy of Michelle Reilly

The first field season was completed in the summer of 2012. Thirty-nine sites with 468 cameras were set up in seven counties around the San Francisco Bay in Northern California. Study sites ranged from National and State Parks to county and regional parks and open spaces to closed, private ecological preserves.  Preliminary results suggest reinforcement of past research studies. Looking at the data, we see a trend in both number of animals and types of species in areas closed to the public as opposed to areas open to the public. Further analysis will be used to investigate these trends in relationship to other variables such as size of the natural area, proximity to urban edge, and topographic ruggedness of the study site.

This summer, we will continue sampling but in a slightly modified design. This will allow us to use the insight from the first season and more efficiently sample the region. With this modified design, I believe we will be able to set up more sites and also sample parks and natural areas which we couldn’t before, further adding to the robust study design.

To learn more about this ongoing research project, visit:

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