Killer whales, blind bats, discriminating dolphins, ma...(e of obstacles/targets which is coded by...)

Date:6/25/2008

e of obstacles/targets, which is coded by the time delay between call and echo. Yet during flight, such accuracy is perturbed -- first because bats call and receive echoes at different positions and second because echoes are modified by Doppler shifts, according to Marc Holderied (marc.holderied@bristol.ac.uk) of the University of Bristol, who studies how flying bats compensate for these sorts of ranging errors.

Holderied has found that combining the two types of errors -- both of which depend upon flight speed -- results in an interesting spatial distribution of the combined ranging errors. Objects at one particular distance from the bat have zero ranging errors, while ranging errors increase for closer or more distant objects. This distance of zero ranging error depends on signal design, in particular the sweep rate, according to Holderied. By adjusting signal design, flying bats could shift this distance adaptively to their target of interest. Because this has similarities with focusing -- accommodation in vision -- this distance is called distance of focus.

Holderied will report on new results from his studies of how 18 different species of bat control the spatial distribution of ranging errors by signal sweep rate. "The challenging task is to relate their echolocation behavior to their flight behavior, particularly with respect to obstacles and prey," he says. To that end, he employs 3D tracking techniques combined with 3D laser scans of bat habitats to study their adaptive calling behavior. At the meeting, he will present examples of actual distances of focus for different bat species in different behavioral contexts, such as search flight, obstacle avoidance, and target approach.

Paper 2pABa9, " Acoustic focussing: how flying bats control spatial distribution of Doppler-ranging errors by signal sweep rate" will be presented at 6:20 p.m. on Tuesday, July 1 in room 342B.

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Contact: Jason Bardi jbardi@aip.org 301-209-3091 American Institute of Physics Source:Eurekalert

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