Echolocation click discrimination for three killer whale ecotypes in the Northeastern Pacific

Area of Science:

• Marine Biology
• Bioacoustics
• Animal Communication

Background:

• Three killer whale (Orcinus orca) ecotypes inhabit the Northeastern Pacific: residents, transients, and offshores.
• These ecotypes exhibit unique pulsed call repertoires, enabling discrimination in passive acoustic data.

Purpose of the Study:

• To characterize ecotype-specific echolocation clicks from Northeastern Pacific killer whales.
• To assess the potential of echolocation click properties for differentiating killer whale ecotypes.

Main Methods:

• Passive acoustic monitoring using seafloor-mounted sensors at shallow and deep locations off Washington state.
• Analysis of echolocation clicks from killer whale encounters previously assigned to ecotypes based on pulsed call matching.

Main Results:

• All killer whale ecotypes exhibited echolocation clicks with energy peaks between 12 and 19 kHz.
• Resident clicks had sub-peaks at 13.7 and 18.8 kHz; offshore clicks peaked at 14.3 kHz; transient clicks were rare with lower peak frequencies (12.8 kHz).
• Inter-click intervals (ICIs) were similar for resident and offshore whales at shallow sites but longer and more variable for offshore whales at deep sites; transient ICIs were not clearly discernible.

Conclusions:

• Echolocation click properties, particularly peak frequencies and sub-peaks, can distinguish resident and offshore killer whale ecotypes.
• Transient killer whale echolocation may not be sufficiently distinct for reliable identification in monitoring applications when used in isolation.