Ecotourism has become a booming, if controversial, business. Although advocates argue it can benefit conservation, some studies have suggested that the development and disturbance that tag along with tourists can have harmful impacts on wildlife. Now, two researchers find that chatting visitors can scare away the very tropical birds they’ve come so far to experience.

The mountainous forests of the Tambopata region in southeastern Peru have become an nature tour hotspot, Daniel S. Karp of Stanford University in California and Roger Guevara of INECOL in Mexico report in the current issue of Biotropica. Between 1995 to 2005, the number of ecotourists grew by 22% per year, to nearly 40,000 visitors a year. The number of ecotourist lodges, meanwhile, rose from 3 in 1990 to 37 in 2008. Lodges now manage more than 54,000 hectares of land, which are often laced with trails built especially for visitors.

To see how local birds are responding to the growing groups of tourists, Karp and Guevara recorded visitors conversing in a room, then played the tapes back while walking along trails through two kinds of forests. One was a frequently visited tract near an ecolodge; the other was in a rarely visited preserve. At multiple points along each trail, they surveyed all the birds they could see or hear after a moment of silence, and after playing a brief snippet of their recording at 50 decibels – a typical level for talking tourists – and at 60 decibels, about equal to the volume of an excited child.

Turns out the birds in both forests just didn’t want to hear it. After playing the recordings, the number of individual birds detected by the researchers declined by 35 to 39 percent; the number of species they detected dropped 33% to 37%. Some birds stopped singing (37%), while others fled out of sight (44%). Insect-eating birds appeared to be the most sensitive, perhaps because they have particularly acute hearing. The researchers also speculate that the birds may associate noise with predators.

The researchers worry that “increasing secretive behavior may have negative consequences for birds.” They may stop singing during the dawn chorus, for instance, perhaps reducing their ability to attract mates and drive away rivals. And although ecotourism “has much worth, and is clearly preferable to large-scale, exploitive practices such as commercial agriculture, mining, and timber harvesting… (A)s currently practiced, [it] may not be the savior of sensitive species.”

There may be an easy win-win solution for tourists in Peru, however: silence. By shutting up, tourists would disturb fewer birds and “silence would probably result in tourists encountering more wildlife, increasing their perceived return on investment. Further, wildlife may continue to frequent tourist areas, benefiting the lodges’ future economic viability.” David Malakoff

Source: Karp, D., & Guevara, R. (2010). Conversational Noise Reduction as a Win-Win for Ecotourists and Rain Forest Birds in Peru Biotropica DOI: 10.1111/j.1744-7429.2010.00660.x

Image © Sophia Tsibikaki