Speed Dating Basking Sharks
Nov 17 2022
Its been a great year for basking sharks in both conservation and research! New research published this year unveils some fascinating insights to basking shark behaviour, and we were so happy to have been able to contribute to this study. This behaviour we’ve observed over the years around the Hebrides, has now helped to understand complex basking shark courtship.
What is a basking shark ‘torus’?
Basking sharks have been observed swimming in tight circles, mouth closed, showing subtle movements with some sharks exhibiting differing colours. This is unusual behaviour for basking sharks, when we see them on the surface they are usually feeding solitary or in small groups. It is thought that these circling aggregations are a courtship ritual and that the circle descends deeper in the water where potentially mating occurs. Although elusively, mating has never been recorded yet!
The behaviour has been termed a ‘torus’. In geometry torus is described as a revolving circle around an axis – also known as a donut and relates to the shape of the basking sharks swimming in a circle. (But we prefer the term sharknado!)
We’ve observed torus in both a small number of individuals and larger groups, many of which were feeding before hand and conducting normal shark swimming behaviour. It’s unknown what trigger leads to the torus forming. Larger torus’s have also been observed off the Irish coast which forms the bulk of the study as there was especially large aggregations observed here over the years of writing.
The paper is called ‘Circles in the sea: annual courtship “torus” behaviour of basking sharks Cetorhinus maximus identified in the eastern North Atlantic Ocean.’ It’s open access and can be found here
Shane Wasik & Lois Flounders from Basking Shark Scotland worked on contributing to the final study with our observations from the Hebrides. Thank you to Luke Saddler & Tammi Warrender (former staff), Will Clark, Rudolf Svensen and Bertie Gregory (guests) for sharing footage that was included in the study.
See below for a videos made to assist in the interpretation of the paper.
In addition if you wonder what happens when the sharks descend, there has been some footage captured from a camera tagged basking shark during a study by Nature Scotland. Although it did not record actual copulation it’s another piece of the basking shark puzzle!
