Echolocating bats fly around in darkness emitting ultrasonic sounds and listening for the echoes that return from things like tasty insects flying nearby. The bats use the echo information to locate the insects and chase them with breathtaking high speed maneuvers. I was interested in knowing what kind of computations the bat's brain may be doing in order to turn sensory information into a flight strategy. I designed and built apparatus to measure the sonar beam patterns of flying bats. I made observations of bat flight behavior and mathematically modeled the flight strategies they use to capture insects. I showed how the bat's acoustic gaze (where it directs its sonar beam) is related to its flight pattern and may be used to gain insight into what the bat is planning. I also showed how the bat optimizes its flight strategy to chase unpredictably moving insects in order to improve its chances of a quick, successful capture.
In addition to formal scientific papers, I also wrote two informal essays on my work with bats. This essay was done on invitation for Imagine magazine and this essay was by invitation for the Intentional Society for Neuroethology newsletter.
Publications
[With Cynthia F. Moss, Timothy K. Horiuchi, P.S. Krishnaprasad, Jeffrey D. Triblehorn and David D. Yager]
Kaushik Ghose, Jeffrey D. Triblehorn, Kari Bohn, David D. Yager and Cynthia F. Moss (2009) Behavioral responses of big brown bats to dives by praying mantises. J. Exp. Biol. 212,693 -703. (fulltext, pdf)
We got featured in the "Inside JEB" section with this blurb!
Kaushik Ghose, Timothy K. Horiuchi and Cynthia F. Moss (2007) Flying big brown bats emit a beam with two lobes in the vertical plane. Journal of the Acoustical Society of America, 122(2), 3717-3724. (pdf)
Kaushik Ghose (2006) Sonar Beam Direction and Flight Control in an Echolocating Bat. PhD. Thesis (pdf)
Kaushik Ghose, Timothy K. Horiuchi, P.S. Krishnaprasad and Cynthia F. Moss (2006) Echolocating bats use a nearly time-optimal strategy to intercept prey. Public Library of Science: Biology, 4(5), (pdf)
Echolocating bats adopt an interesting strategy when chasing erratically moving insects. The approach they use can be shown to minimize the time to intercept, even though the motion of their prey is random (erratic). This form of interception is called parallel navigation and was described by engineers working on the very first guided missiles. It appears that bat's had them beat by a few million years.
The idea that bats use a parallel navigation strategy similar to guided missiles made for good copy on The Hindu, Science Daily and other parts of the internet.
Kaushik Ghose and Cynthia F. Moss (2006) Steering by Hearing: A Bat’s Acoustic Gaze Is Linked to Its Flight Motor Output by a Delayed, Adaptive Linear Law. Journal of Neuroscience, 26(6), 1704-1710. (pdf) Supplementary video S1, S2 , Publicity video.
This paper reports an interesting link between where a bat "looks" with its sonar beam and where is ends up flying. Somewhat like humans "look where they go" bats seem to "point before they fly" - directing their sonar beam to the left or right of their current flight path, before adjusting their flight.
Discovery channel interviewed me as part of a short piece on the Steering by Hearing paper on February 9th 2006.
Kaushik Ghose and Cynthia F. Moss (2003) The sonar beam pattern of a flying bat as it tracks moving and stationary prey. Journal of the Acoustical society of America, 114(2), 1120-1131. (pdf) Beam pattern animations
This paper reports the first study of how a species of echolocating bat points its sonar beam at insects it is trying to catch. The paper reports parallels between how humans and other visually guided animals gaze at objects they are interested in and how a bat "looks" at objects with its sonar beam.
The sonar beam animations gained notoriety by winning first prize (non interactive media) in the Science and Engineering Visualization Challenge hosted by Science magazine and the NSF. The word diptych, if you wondered like I did, means any object with two flat plates attached at a hinge.