Demonstration of adaptation in beluga whale echolocation signals

TLDR

Kaneohe Bay’s ambient noise is 12–17 dB louder than San Diego Bay. The same beluga whale’s echolocation signals were recorded in San Diego Bay and later in Kaneohe Bay. After moving to Kaneohe, the whale raised its signal frequency by about an octave—from 40–60 kHz to 100–120 kHz—expanded bandwidth, and increased intensity by up to 18 dB, providing the first quantitative evidence of cetacean biosonar adaptation.

Abstract

The echolocation signals of the same beluga whale (Delphinapterus leucas) were measured first in San Diego Bay, and later in Kaneohe Bay, Oahu, Hawaii. The ambient noise level in Kaneohe Bay is typically 12 – 17 dB greater than in San Diego Bay. The whale demonstrated the adaptiveness of its biosonar by shifting to higher frequencies and intensities after it was moved to Kaneohe. In San Diego, the animal emitted echolocation signals with peak frequencies between 40 and 60 kHz, and bandwidths between 15 and 25 kHz. In Kaneohe, the whale shifted its signals approximately an octave higher in frequencies with peak frequencies between 100 and 120 kHz, and bandwidths between 20 and 40 kHz. Signal intensities measured in Kaneohe were up to 18 dB higher than in San Diego. The data collected represent the first quantitative evidence of the adaptive capability of a cetacean biosonar system.