Animals use sound for many purposes. Some hear only to become aware of their surroundings. Others produce sounds and listen to the transmissions of conspecifics in order to communicate or attract and locate mates. A few specialized animals use the echoes of their sounds to orient and navigate their environment and to search for and intercept prey.
We study two behavioral models – echolocating bats and chorusing frogs – using a variety of observational techniques in the field. Our most powerful tool is a custom method of detecting and localizing sounds using our own passive sonar. We setup an array of microphone towers and carefully measure the position of each receiver. By measuring the propagation differences of sounds to each of the microphones, we are able to locate animals in 3D whenever they make a sound.
Using this system, we track bats as they fly and hunt using sonar, even in the presence of interference and jamming. After tracking a bat, we construct an acoustic filter that acts like a virtual microphone following a bat's path through space. This technique allows us to follow the spatial behavior of bats and groups of bats, and ask how the spatial distributions of bats, prey and clutter affect echolocation behavior.
In a similar fashion, we localize the calls of chorusing male frogs as they try and attract female conspecifics. By setting a microphone array next to a pond, we are able to localize and listen to individual male frogs as they both compete with and team up with their neighbors. These studies allow us to ask how the frogs time their calls and how the calling behavior has evolved as equilibrium of competition and teamwork.
We conduct field work in the fields and around the ponds of New England, in Japan and in Belize.