Professor Peter Teglberg Madsen

TY - JOUR

T1 - Biosonar adjustments to target range of echolocating bottlenose dolphins (Tursiops sp.) in the wild

AU - Jensen, Frants Havmand

AU - Bejder, Lars

AU - Wahlberg, Magnus

AU - Madsen, Peter Teglberg

PY - 2009

Y1 - 2009

N2 - Toothed whales use echolocation to locate and track prey. Most knowledge of toothed whale echolocation stems from studies on trained animals, and little is known about how toothed whales regulate and use their biosonar systems in the wild. Recent research suggests that an automatic gain control mechanism in delphinid biosonars adjusts the biosonar output to the one-way transmission loss to the target, possibly a consequence of pneumatic restrictions in how fast the sound generator can be actuated and still maintain high outputs. This study examines the relationships between target range (R), click intervals, and source levels of wild bottlenose dolphins (Tursiops sp.) by recording regular (non-buzz) echolocation clicks with a linear hydrophone array. Dolphins clicked faster with decreasing distance to the array, reflecting a decreasing delay between the outgoing echolocation click and the returning array echo. However, for interclick intervals longer than 30–40 ms, source levels were not limited by the repetition rate. Thus, pneumatic constraints in the sound-production apparatus cannot account for source level adjustments to range as a possible automatic gain control mechanism for target ranges longer than a few body lengths of the dolphin. Source level estimates drop with reducing range between the echolocating dolphins and the target as a function of 17 log(R). This may indicate either (1) an active form of time-varying gain in the biosonar independent of click intervals or (2) abias in array recordings towards a 20 log(R) relationship for apparent source levels introduced by a threshold on received click levels included in the analysis.

AB - Toothed whales use echolocation to locate and track prey. Most knowledge of toothed whale echolocation stems from studies on trained animals, and little is known about how toothed whales regulate and use their biosonar systems in the wild. Recent research suggests that an automatic gain control mechanism in delphinid biosonars adjusts the biosonar output to the one-way transmission loss to the target, possibly a consequence of pneumatic restrictions in how fast the sound generator can be actuated and still maintain high outputs. This study examines the relationships between target range (R), click intervals, and source levels of wild bottlenose dolphins (Tursiops sp.) by recording regular (non-buzz) echolocation clicks with a linear hydrophone array. Dolphins clicked faster with decreasing distance to the array, reflecting a decreasing delay between the outgoing echolocation click and the returning array echo. However, for interclick intervals longer than 30–40 ms, source levels were not limited by the repetition rate. Thus, pneumatic constraints in the sound-production apparatus cannot account for source level adjustments to range as a possible automatic gain control mechanism for target ranges longer than a few body lengths of the dolphin. Source level estimates drop with reducing range between the echolocating dolphins and the target as a function of 17 log(R). This may indicate either (1) an active form of time-varying gain in the biosonar independent of click intervals or (2) abias in array recordings towards a 20 log(R) relationship for apparent source levels introduced by a threshold on received click levels included in the analysis.

KW - Tursiops

KW - Delfin

KW - Hval

KW - Ekkolokation

KW - Biosonar

KW - Lydproduktion

KW - Automatic Gain Control

KW - Tursiops

KW - Dolphin

KW - Whale

KW - Echolocation

KW - Biosonar

KW - Sound Production

KW - Automatic Gain Control

U2 - 10.1242/jeb.025619

DO - 10.1242/jeb.025619

M3 - Journal article

C2 - 19329740

VL - 212

SP - 1078

EP - 1086

JO - BRITISH JOURNAL OF EXPERIMENTAL BIOLOGY

JF - BRITISH JOURNAL OF EXPERIMENTAL BIOLOGY

SN - 0022-0949

ER -