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