Last May, we were fortunate to sight a group of six male sperm whales logging and resting at the surface. At Futurismo we take every opportunity to collect data, to learn more and contribute to the scientific community. We decided to put our hydrophone in the water. We not only found out that the six males were communicating between each other, but we also had the opportunity to record it. Such an uncommon sighting being recorded was an ideal way to celebrate the 2021 Year of Sound, a global initiative set by the International Commission for Acoustics (ICA) to highlight the importance of sound in different aspects of life on Earth.
Little is known about the social life of male sperm whales. Generally, male sperm whales remain in their family group until they become juveniles. Young males gather then to form bachelor groups before they reach adulthood, and after, they segregate to live mainly solitary (Whitehead, 2003). A recent study by Kobayashi et al. (2020), demonstrated how male sperm whales from Nemuro Strait in Japan can maintain long-term associations, forming long-term companionship and foraging in social proximity to each other. Some encounters, such as multiple strandings, also suggest the possible strong social bonds between male sperm whales, even with individuals from different breeding regions (Kobayashi et al. 2020; Autenrieth, 2018).
But what about the Azores?
The sighting of this group of males was somehow unusual in the Azores. Here, adult male sperm whales are sighted occasionally mostly alone, or probably to mate with females (van der Linde & Eriksson, 2019), while younger males are frequently sighted within their family group (Clarke, 1956). However, bachelor groups are not sighted so often around here, and in this case, they really seemed like adult individuals!
After analysing the sound, we were able to distinguish three types of clicks: (1) some more intense than the rest, with 4 seconds interclick intervals (ICIs), which can be heard throughout the entire recording (Graph. 1); (2) other less intense clicks resembling a sound like a dropping marble bouncing on solid ground, with shorter interval pauses as the time passes by, which overlapped with the former sound (Graph. 1); and (3) three last repetitions of a sound pattern of fast clicks in the end of the recording, resembling a rusty door opening with 2 clicks more separated from the other 6-7 clicks (Graph. 1,2).
We tried to link some of these sounds with a certain described sound type. The first clicks may possibly be slow clicks (Wahlberg, 2002; Carwardine 2020). They are likely to be used as an acoustic display in breeding grounds, such as the Azores, in order to show competition abilities and maturity (Weilgart & Whitehead, 1988). The rusty door-like clicks resemble surface creaks, which may be used to locate objects in the water (Carwardine, 2020).
In the last few months, at Futurismo we have started to record sounds regularly, to try to understand them and to slowly discover a bit more about the acoustic realm of the sperm whale. A long way to go, but the hardest first step, which is starting!, is done 😉
Maybe one day we will be able to find out if these males were saying:
- I am better than you to mate with this girl (slow clicks).
- How interesting is this hydrophone in the water! (scanning surroundings with surface creaks).
- Great conversation today with my friends (codas).
We will clarify these conclusions in the course of the following months with our biologist’s crew and the partners working alongside us. So keep tuned to follow the story!
Autenrieth M. et al., (2018), Putative origin and maternal relatedness of male sperm whales (Physeter macrocephalus) recently stranded in the North Sea, Mammalian Biology, Volume 88, pages 156-160, ISSN 1616-5047, link: <https://www.sciencedirect.com/science/article/pii/S1616504717301337>
Carwadine, M., (2020), Handbook of whales, dolphins and porpoises, BLOOMSBURY WILDLIFE, London, ISBN HB: 978-1-4729-0814-8.
Clarke, R.B., 1956. Sperm Whales of the Azores. PhD Thesis. University Press.
Kobayashi H, Whitehead H & Amano M., (2020), Long-term associations among male sperm
whales (Physeter macrocephalus), PLoS ONE 15(12): e0244204, link: <https://doi.org/10.1371/journal.pone.0244204>
van der Linde, M.L. & Eriksson, I.K. (2020), An assessment of sperm whale occurrence and social structure off São Miguel Island, Azores using fluke and dorsal identification photographs. Marine Mammal Science, 36(1), 47-65. https://doi.org/10.1111/mms.12617
Wahlberg M., (2002), The acoustic behaviour of diving sperm whales observed with a hydrophone array, Journal of Experimental Marine Biology and Ecology, Volume 281, Issues 1–2, pages 53-62, ISSN 0022-0981, link: https://www.sciencedirect.com/science/article/pii/S0022098102004112
Whitehead, H. (2003). Sperm whales: social evolution in the ocean. University of Chicago press.
Weilgart L. S. & Whitehead H., (1988), Distinctive vocalizations from nature male sperm whales (Physeter macrocephalus), Canadian Journal of Zoology, link <https://cdnsciencepub.com/doi/10.1139/z88-282>