Inter and intra specific variation in echolocation signals among odontocete species in the Northwest Atlantic, the Temperate Pacific and Hawaii

Abstract

Odontocete species use echolocation signals (clicks) to forage and navigate. The aim of this study is to explore inter- and intra-specific variation in clicks among odontocete species in the Northwest Atlantic, Temperate Pacific, and Hawaii. Clicks were examined for seven species of odontocetes—bottlenose dolphins, common dolphins, striped dolphins, rough-toothed dolphins, pilot whales, Risso’s dolphins, and Cuvier’s beaked whales. Specially developed PAMGuard tools were used to automatically measure a suite of click parameters. Seven parameters were compared within and between species; duration, 10 dB bandwidth, 3 dB bandwidth, center frequency, peak frequency, sweep rate, and number of zero crossings. Significant differences in duration, center, and peak frequency were evident between species within study areas (Dunn’s test with Benjamini-Hochberg adjustment <0.05). Geographic variation in click parameters between the three study regions was also examined. Results showed statistically significant pair-wise differences between geographic regions for almost all echolocation click parameters and species (Dunn’s test with Benjamini-Hochberg adjustment <0.05). Results suggest species-specific differences in clicks among odontocetes and indicate that geographic variation exists for multiple species. The ecological significance of these findings will be discussed along with implications for classifier development.