Extending their vibration-sensitive whiskers, the mammals are almost as efficient at pursuing their quarry as they would be if guided by sight. Wolf Hanke and his colleagues from the University of Rostock, Germany, are fascinated by how harbour seals perceive the world through their flow-sensitive vibrissae.
Having already found that seals can pick up and follow fish wakes up to 35 seconds after the prey has passed and knowing that a fish's size and shape can dramatically affect its wake structure, graduate student Sven Wieskotten decided to find out how well seals can distinguish between the wakes of objects with different shapes and sizes. The team publishes their discovery that harbour seals can detect differences in the wakes generated by differently shaped objects using only their whiskers in The Journal of Experimental Biology at http://jeb.biologists.org/content/214/11/1922.abstract
Teaming up with Henry the harbour seal at the Marine Science Centre, Germany, Hanke, Wieskotten and their colleagues, Lars Miersch and Guido Dehnhardt, began testing Henry's ability to distinguish between the wakes of differently sized paddles. The researchers blindfolded Henry and covered his ears, then they swept a paddle through a large box in Henry's enclosure and allowed him to enter it 3ƒn seconds later. Having trained Henry to press a target outside the enclosure when he recognised the wake of a standard paddle and to press a different target when he recognised the wake from a larger or smaller paddle, the team found that Henry could distinguish between paddles that differed by as little as 2.8cm in width.
Then, the team tested which aspects of the wake the seal picked up on. 'We randomised the speeds of the paddles so that the maximum flow velocity wasn't a distinguishing cue for the widest paddles, but the structure of the wake had to be recognised by the seal and he could do that too, but with slightly less accuracy,' remembers Hanke.
Next, the team varied the paddle shapes and asked Henry to distinguish between the wakes of triangular, cylindrical, flat and undulating paddles. The seal successfully distinguished between the flat and cylindrical paddles, the flat and undulating paddles and the undulating and cylindrical paddles after they were swept through the enclosure. However, he had problems distinguishing the triangular paddle from the undulating or cylindrical shapes.
Having found that Henry can distinguish between the wakes of different passing objects and investigated the structure of each paddle's wake with digital particle image velocimetry, Hanke says, 'It is difficult to tell which part of the wake serves the animal most and which aided only a little.' So, Hanke is keen to test Henry's responses to single vortices to find out which wake components might give a fish's size and shape away. He explains that hunting seals have to optimise the amount of energy that they ingest while hunting so, if a seal can distinguish between small skinny fish ¡V which cost too much to pursue ¡V and the perfect lunch based on their wakes alone, that could improve its hunting efficiency enormously.
IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org
REFERENCE: Wieskotten, S., Mauck, B., Miersch, L., Dehnhardt, G. and Hanke, W. (2011). Hydrodynamic discrimination of wakes caused by objects of different size or shape in a harbour seal (Phoca vitulina). J. Exp. Biol. 214, 1922-1930.
New technology offers fast peptide synthesis
28.02.2017 | Massachusetts Institute of Technology
Biofuel produced by microalgae
28.02.2017 | Tokyo Institute of Technology
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
28.02.2017 | Life Sciences
28.02.2017 | Power and Electrical Engineering
28.02.2017 | Information Technology