Male Sperm Whales' Slow Clicks Are the Loudest Communication Signals of Any Mammal, Aarhus Study Finds
A study led by Aarhus University finds male sperm whales' slow clicks exceed 200 dB and can carry up to 70 kilometers, the loudest mammalian communication signal recorded.
Overview
Male sperm whales produce slow, low-frequency clicks that register as the loudest communication signal of any mammal, according to a study from researchers at Aarhus University published in the Annals of the New York Academy of Sciences, as reported by Phys.org. The paper, titled “Extreme Rhythm Keeping in Long-Range Slow Click Communication of Sperm Whales,” appears in Volume 1559, Issue 1, Article e70289 of the journal, according to the study’s listing on Aarhus University’s research portal.
What We Know
- The slow clicks reach source levels ”> 200 dB re 1 µPa (peak-peak)” and were found to be “the loudest communication signal of any mammal,” according to the study abstract published on Aarhus University’s research portal.
- Under deep-ocean conditions, the clicks have an estimated “active space of up to 70 km,” or 70 kilometers (43 miles), the same abstract states, a figure also reported by Phys.org.
- The clicks are “highly rhythmic at rates of 0.1-0.3 Hz,” which the researchers describe as “an order of magnitude slower than other rhythmic communication signals among mammals and birds,” according to the study abstract. Phys.org reports this translates to five to 10 seconds between each click.
- These slow clicks are distinct from the echolocation clicks sperm whales use to hunt prey; they are instead communication signals, according to Phys.org.
- The clicks are produced through a nasal complex that in a fully grown male “can weigh more than five tonnes (11,000 pounds),” according to Phys.org.
- “What is extreme about slow clicks is that the whales can produce them with long time intervals between them. And they can do it very rhythmically. And over those distances. It is really the combination of the three things that is extreme: the strength, the rhythm and the range,” said Simone Videsen, a postdoctoral researcher at Aarhus University, according to Phys.org.
- The researchers propose the clicks may function as an “honest advertisement” of a male’s size, since “a big nose sits on a big male, and a big nose will produce a lower-frequency click,” said Professor Peter Teglberg Madsen, a senior author of the study, also from Aarhus University, according to Phys.org.
- Videsen said the function of the signal remains an open question: “Could it be linked to honest advertisement, sexual selection, territorial enforcement or something else entirely?” according to Phys.org.
- The study abstract proposes that “slow click production is a low entropy, long-range communication signal that may offer honest advertisement through rhythm-keeping to distant receivers,” according to the Aarhus University research portal.
What We Don’t Know
- The researchers say they don’t know exactly how the whales maintain such precise timing between clicks separated by several seconds. The study abstract speculates that whales “may be achieved by the sperm whales using extrinsic echo information from the environment to maintain extreme isochrony,” according to the research portal listing. Madsen cautioned that this remains unproven: “We do not know whether they do this, but it would be a way for them to use the environment as a stopwatch,” he said, according to Phys.org.
- The exact biological function of the slow clicks — whether tied to mate attraction, rivalry, territory, or another purpose — has not been established.
- Madsen cautioned against over-interpreting the findings: “But I warn against making them more human than the data can support,” he said, according to Phys.org.