Ocean News

Basking in newfound glory:

19th October 2018

The latest research shows that filter-feeding basking sharks can breach like predatory great white sharks

Photo © Martin Prochazkacz | Shutterstock

The basking shark, cruising the oceans with its mouth agape, is an ocean image perhaps least synonymous with speed and power. Indeed, our perception of large filter feeders is that they seem to move through the water with a languid behaviour best adapted to scoop mouthfuls of microscopic plants and animals – plankton – as they swim.

Photo © Martin Prochazkacz | Shutterstock

Images of powerful sharks bursting above the water’s surface are typically reserved for the mackerel sharks: the predatory mako and great white sharks. These streamlined sharks with their perfectly adapted shape seem made to ambush their prey, lolling at the water’s surface, with a burst of speed and breach from below.

Comparing basking (left panel) and white (right panel) sharks. (a) The external morphology of these species is similar; (b) breaches by these species; (c) vertical breach velocity as determined from video analysis; means and one standard deviation. Illustrations reproduced with permission of Marc Dando, and breaching images credited to Bren Whelan and White Shark Africa™. (Online version in colour.)

Now, scientists have used cameras attached to basking sharks to glimpse into these animals lesser-known behaviours, investigating observations that basking sharks use improbable speed and power to breach. The paper, led by Emmett Johnston from Queen’s University in Belfast and the Irish Basking Shark Study Group, was published in September in Biology Letters. They compared the footage to that captured by co-author Alison Kock from the University of Cape Town, of great white sharks. The two different species, while they have totally different feeding strategies, have rather similar body shapes. They found that basking sharks breach at a similar angle and speed to great white sharks!

Photo © Martin Prochazkacz | Shutterstock

Why on earth would basking sharks need to breach at all, if their food hangs mostly suspended in the water column? The paper’s authors surmise that the behaviour might have some social communication purpose. It might be linked to any number of other functions, from dominance to mating displays or removing parasites from their skin. Whatever the reason, the finding certainly challenges our perception of the basking shark as langorous filter feeders and suggests that the same kind of body shape can be used for vastly different life histories!

You can read the full paper here.

Reference:  Johnston EM, Halsey LG, Payne NL, Kock AA, Iosilevskii G, Whelan B, Houghton JDR. 2018. Latent power of basking sharks revealed by exceptional breaching events. Biol. Lett. 14: 20180537.