Hungry deer in the northeastern US are likely changing the acoustics （音效）of their forests by eating up bushes, small trees and other leafy plants that normally would affect the transmission（传播）of natural sounds such as bird calls.
Megan Gall, an ecologist at Vassar College who studies how the environment shapes animals' senses, showed curiosity about the possibility after talking with a couple of colleagues who were studying how browsing（吃草的）deer could transform a forest ecosystem by eating up the entire lower level of leafy plants.
Gall already knew that sound travels differently through open fields than through the woods. She also had previously studied how human noise can influence wildlife communication. Confused about how deer might change what other animals hear, she decided to do some experiments in a couple of forested areas that her colleagues had set up for their deer studies.
One area was fenced off in a way that kept out the deer. The other area was marked off but left open so that deer could enter and browse. Gall and two students set up audio equipment around these areas. They broadcast different sounds and checked to see how those sounds changed after traveling through each environment. They checked sounds that they sent through the lowest level of the forest, in the middle-level of the forest and at angles going from the ground upward.
The results, published in the journal PLOS One , show that the structure （结构）of a sound changed a lot when it was traveling through an area that the deer hadn't snacked on.
“When deer were browsing, we actually found that the sound was clearer,Gall says.
“The challenge for further study is to find places that have not been browsed," he says, “to see if any of these changes have already occurred. Deer are so pervasive. You'd really have to look hard to find areas that have not been browsed. ”
