Aloha colleagues,
For your interest, we have just published the following article on
dolphin echolocation:
Branstetter, B. K., Mevissen S. J., Pack, A. A., Herman, L. M.,
Roberts, S. R., and Carsrud, L. K. (2007). Dolphin (Tursiops
truncatus) echoic angular discrimination: Effects of objects
separation and complexity. Journal of the Acoustical Society of
America, 121, 626-635.
Summary of
article
A
bottlenose dolphin was tested on its ability to echoically
discriminate horizontal angular differences between arrays of
vertically oriented air-filled PVC rods. The blindfolded dolphin was
required to station in a submerged hoop 2 radial m from
the stimuli and indicate if an array with two rods (S+) was to the
right or the left of a single rod (S-). The angular separation between
the two rods (thetaw) was held constant within each experiment while
the angle between the S+ and the S- stimuli (thetab) varied to produce
angular differences (Deltatheta=thetab-thetaw) ranging from 0.25 to
4°. In experiment I, thetaw was maintained at 2° and in experiment
II, thetaw was maintained at 4°. Resulting 75% correct thresholds
(method of constant stimuli) were 1.5 and 0.7°, respectively. The
two main findings of this study are: (1) decreasing the number of
targets does not aid in localization, and (2) increasing the space
between the rods enhances localization. Taken as a whole, the
experiments suggest dolphins have a well-developed ability to resolve
spatial information through sonar.
Reprint pdfs may be obtained from
Brian Branstetter at branstet@hawaii.edu or from Adam Pack at
pack@hawaii.edu.
Wishing you all a happy, healthy, and peaceful 2007,
Adam A. Pack, Ph.D.
Vice President and Research and Education Program Manager, The Dolphin
Institute
Affiliate Graduate Faculty, University of Hawaii at Manoa
P.O. Box 700694
Kapolei, HI 96709
808-679-3690