Passive Acoustics in the Gulf of Mexico Takes First Steps in Studying Mysterious Beaked Whales

 

Natalia Sidorovskaia - nas@louisiana.edu
Dept. of Phys., Univ. of Louisiana at Lafayette

UL Box 44210

Lafayette, LA 70504‐4210

 

George E. Ioup

Juliette W. Ioup

Dept. of Physics, Univ. of New Orleans

New Orleans, LA 70148

Christopher O. Tiemann

ARL, Univ. of Texas at Austin

Austin, TX 78713

Alexander E. Ekimov

James Sabatier

National Ctr. for Physical Acoustics, Univ. of Mississippi

Oxford, MS 38677

Popular version of paper 5aAB2

Presented Friday morning, April 23, 2010

159th ASA Meeting, Baltimore, MD

 

 

Over several years the Littoral Acoustic Demonstration Center (LADC), a consortium comprising the University of New Orleans, University of Louisiana at Lafayette, University of Southern Mississippi, University of Texas at Austin, and US Navy Labs at Stennis Space Center has collected an extensive acoustic library of marine mammal phonations in the Northern Gulf of Mexico, including recent (first in the Gulf of Mexico) recordings of Cuviers and Blainvilles beaked whale clicks. Understanding beaked whale social organization, behavior, and their extremely sensitive reaction to human-made sounds in the ocean (including reported mass strandings during naval sonar exercises) is a challenge for scientists from different disciplines, because of animals evasive nature, long deep dives, and the acoustic characteristics of produced sound. Since acoustics is a primary communication mechanism for these whales, LADC scientists have been developing tools to process recorded beaked whale phonations to reconstruct acoustic portraits of individuals in a group, hoping to understand how the animals themselves recognize each other during dives. In this talk we report preliminary results on using a new processing algorithm (multi-band cadence frequency analysis) to identify the temporal evolution of individual rhythmic patterns in overlapping trains of simultaneously echolocating beaked whales in a group while the group is diving and seeking prey. The proposed algorithm has several advantages. It provides species-related association cues for complex cluttered acoustic environments where different species phonate with similar inter‐click intervals, which allows improved performance of a passive acoustic detector for beaked whales. We also investigate the capabilities of the algorithm to estimate the number of animals in a diving group and to associate echolocation signals with particular individuals. The proposed approach is beneficial for passive acoustic studies of beaked whale populations and social behavior and may contribute to understanding the acoustic communication of these evasive animals.