The Boing

The Boing is a distinctive underwater whale vocalization. It has a long and intriguing history in marine acoustics, with its source remaining a mystery for decades before finally being attributed to minke whales.

The "boing" sound was first documented in the 1950s by G. M. Wenz, who recorded it using submarines off the coast of San Diego, California, and in Hawaiian waters, as well as from bottom-mounted hydrophones off Kāneʻohe, Hawaii. For many years, the origin of this unique sound remained unknown, though it was suspected to be produced by a whale species. Early observations by Thompson and Friedl in 1982, using hydrophones off Oʻahu, noted two distinct calling states with different inter-call intervals, suggesting that the sound might be related to acoustic contact between whales. However, due to limited sample size and the inability to localize calls, the exact source and function remained elusive.

It wasn't until the early 2000s that researchers definitively identified the minke whale as the source of the "boing" sound. Specifically, Rankin and Barlow attributed the North Pacific "boing" sound to minke whales in 2002. This discovery was significant because minke whales are notoriously difficult to observe visually due to their small, inconspicuous blows, brief surface times, and solitary nature. Therefore, passive acoustic monitoring (PAM) became a crucial tool for studying their behavior and life history.

Further research, particularly in Hawaiian waters, has shed more light on the characteristics and potential function of the "boing" call. The central North Pacific "boing" call, as opposed to the eastern North Pacific type, is characterized by an onset transient component followed by a long call with both frequency and amplitude modulation, typically lasting around 2.6 seconds. The majority of its energy is concentrated in the 1,350 to 1,440 Hz band, with 115 Hz pulse repetition rate harmonic bands.

Recent studies, such as those conducted at the Pacific Missile Range Facility (PMRF) off Kauaʻi, Hawaiʻi, have utilized extensive passive acoustic monitoring to analyze minke whale "boing" calls. Between August 2012 and July 2017, researchers collected 599 days of data, identifying over 223,000 calls from 2,245 individual minke whale tracks [5]. This research revealed that minke whales exhibit two distinct calling states: a nominal rate with an average inter-call interval (ICI) of approximately 6.85 minutes, and a rapid rate with an average ICI of about 0.63 minutes.

A key finding from these studies is that minke whales are more likely to call at an increased rate when in close proximity to other vocalizing minke whales. This suggests that the "boing" call, while potentially serving as a mating call, may also communicate territoriality, with increased calling rates signaling aggression when other whales approach too closely. This dual purpose is observed in other animal species where vocalizations serve both mating and aggressive functions. The seasonality of the "boing" call in Hawaiian waters, primarily from October to May, further supports its potential role in breeding behavior, similar to humpback whale songs.

The "boing" sound's discovery and subsequent attribution to minke whales have significantly advanced our understanding of these elusive creatures, highlighting the critical role of acoustic monitoring in marine mammal research.

External links

• Minke Whale "boing" at Vimeo