How big is a sperm whale?
There are many ways to find out their size.
For example, diving with them and using a really long meter (not recommended, it can be really hard!).
In a more scientific way, you can actually measure stranded animals. This is a highly precise method. Unfortunately, stranding events can happen. On the 20th of September, 14 individuals stranded on King Island, near Australia. Necroscopies and many analyses will be conducted.
With living animals, other cool stuff can be done. Have you ever thought that you can measure them from photographs? Well, you can do it! It's called photogrammetry and it's a matter of comparison between the animal and a predefined measure, usually the distance between two lasers.
And there's a truly amazing methodology that you probably don't know: measuring them from their clicks! Indeed sperm whale's produce a large variety of sounds, including clicks. These are really short sounds, broadband (in frequency) and highly intese (currently, the most intense! They can almost kill a human, but no such events have been reported). They can produce these sounds thanks to a complex, unique to this species, nasal apparatus (consisting also of the spermaceti organ). You can see a representation in the second picture (Caruso et al., 2015). Amazing right? Dotted lines represent the way this sounds travel through the organ. All this complex mechanism leads to the emission of the sound infront of their head, consisting of different pulses due to the sound reflection in the air sacs. Actually, the time distance (delay) between two subsequent pulses can be related to the size of the spermaceti organ, so of the head and finally of the lenght of the animal. Isn't it so cool? So, just recording their sounds, when they echolocate (when they are searching for food) or when they socialize, can give us the opportunity to measure them.
This incredible discovery come from 1972 with Norris and Harvey. In all these years it developed incredibly, with new discoveries, new approaches (like automated ones, so helpful!) and many publications.
This was the core part of what I did for my Master thesis, with data collected in São Miguel Island, Azores. And also thanks to this work, now I am an intern at the Marine Bioacoustics Lab in Aarhus University, under the supervision of one of the greatest names in Bioacoustics and sperm whales' research.
Life can be really unexpected, right?
𝗥𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲𝘀:
Caruso F, Sciacca V, Bellia G, De Domenico E, Larosa G, Papale E, et al. (2015) Size Distribution of Sperm
Whales Acoustically Identified during Long Term Deep-Sea Monitoring in the Ionian Sea. PLoS ONE 10(12): e0144503. https://doi.org/10.1371/journal.pone.0144503
Madsen, P. T., Payne, R., Kristiansen, N. U., Wahlberg, M., Kerr, I., & Møhl, B. (2002a). Sperm whale sound
production studied with ultrasound time/depth-recording tags. Journal of Experimental Biology, 205(13), 1899-
1906. https://doi.org/10.1242/jeb.205.13.1899
Marcolin, C. (2022). Sviluppo di un protocollo acustico a bordo di navi da whale watching per stimare la taglia di Capodogli a largo di São Miguel, Azzorre. Unige. https://unire.unige.it/handle/123456789/4252
Møhl, B. (2001). Sound transmission in the nose of the sperm whale Physeter catodon. A post mortem
study. Journal of Comparative Physiology A, 187(5), 335-340. https://doi.org/10.1007/s003590100205
Møhl, B., Wahlberg, M., Madsen, P. T., Miller, L. A., & Surlykke, A. (2000). Sperm whale clicks: Directionality and source level revisited. The journal of the Acoustical Society of America, 107(1), 638-648.
Norris, K. S. & Harvey, G. W. A theory for the function of the spermaceti organ of the sperm whale. NASA SP 262,
397–416 (1972). https://ntrs.nasa.gov/.../casi.ntrs.nasa.gov/19720017437.pdf
Whitehead, H. (2003). SPERM WHALES. Social Evolution in the Ocean. University of Chicago press. ISBN:
9780226895185
𝗦𝘂𝗽𝗽𝗹𝗲𝗺𝗲𝗻𝘁𝗮𝗿𝘆 𝗺𝗮𝘁𝗲𝗿𝗶𝗮𝗹 / 𝗔𝗽𝗽𝗿𝗼𝗳𝗼𝗻𝗱𝗶𝗺𝗲𝗻𝘁𝗶:
Madsen, P. T., Wahlberg, M. & Møhl, B. (2002b) Male sperm whale (Physeter macrocephalus) acoustics in a
high-latitude habitat: implications for echolocation and communication. Behav Ecol Sociobiol 53, 31–41.
Rhinelander, M. Q., & Dawson, S. M. (2004). Measuring sperm whales from their clicks: Stability of interpulse
intervals and validation that they indicate whale length. The Journal of the Acoustical Society of America, 115(4),
1826-1831. http://dx.doi.org/10.1121/1.1689346
Teloni, V., Zimmer, W. M., Wahlberg, M. and MADSEN, P. T. (2007). 127 Consistent acoustic size estimation
of sperm whales using clicks recorded from unknown aspects. J. Cetacean Res. Manage, 9(2), 127-136.
http://citeseerx.ist.psu.edu/viewdoc/download...
Watwood, S. L., Patrick J. O. Miller, Johnson, M., Madsen, P. T., & Tyack, P. L. (2006). Deep-Diving Foraging Behaviour
of Sperm Whales (Physeter macrocephalus). Journal of Animal Ecology, 75(3), 814–825.
http://www.jstor.org/stable/3838392
Wahlberg, M. (2002). The acoustic behaviour of diving sperm whales observed with a hydrophone array. Journal
of Experimental Marine Biology and Ecology, 281(1-2), 53-62. https://doi.org/10.1016/S0022-0981(02)00411-2
Ph: Cristina Marcolin.
Nasal apparathus representation (second image) adapted from Caruso F, Sciacca V, Bellia G, De Domenico E, Larosa G, Papale E, et al. (2015) Size Distribution of Sperm
Whales Acoustically Identified during Long Term Deep-Sea Monitoring in the Ionian Sea. PLoS ONE 10(12).
