Making Tags Less of a Drag: Optimising Biologging Devices with Computational Fluid Dynamics

Post provided by WILLIAM KAY

Drag and Biologging Devices

A harbour seal tagged with a biologging device. ©Dr Abbo van Neer

A harbour seal tagged with a biologging device. ©Dr Abbo van Neer

Michael Phelps is one of the most decorated Olympic athletes of all time and the world’s fastest swimmer. And yet, he could swim faster. Wearing the Speedo LZR Racer supersuit Michael Phelps could reduce his hydrodynamic drag, or water resistance, by upwards of 40%. That could increase his swim speed by more than 4%! In competition, that’s the difference between silver and gold. But, if Phelps forgot to remove his “drag socks” – cumbersome footwear designed to increase water resistance for strength training – his speed would be dramatically reduced. He’d be lucky to walk away with bronze!

Professional swimmers have adapted to the use of performance enhancing technologies to decrease their drag, but that’s nothing compared to the adaptations made by wild animals. Creatures in the marine environment have evolved incredible adaptations to decrease drag, such as extreme streamlining in marine mammals and seabirds. This allows them to move underwater as quickly and efficiently as possible. Seals, for example, are pretty ungainly on land, but in the water they’re sleek and rapid. They have a body shape designed to maximise speed while swimming.

When we study marine animals we often use tracking devices, which can be attached using harnesses, glue, or suction-cups. These ‘biologging devices‘, or tags, are similar to Fitbits. Attaching them to animals allows us to record, amongst other things, all of the animal’s movements and behaviours. This information is crucial to understanding their ecology and for improving their conservation management. Continue reading

Remotely Tracking Movement and Behaviour with Biologgers: How to Add Accelerometer Data to the Mix

Post provided by Sam Cox, Florian Orgeret and Christophe Guinet

Animal biologging is a technique that’s quickly becoming popular in many cross-disciplinary fields. The main aim of the method is to record aspects of an animal’s behaviour and movement, alongside the bio-physical conditions they encounter, by attaching miniaturised devices to it. In marine ecosystems, the information from these devices can be used not only to learn how we can protect animals, many of whom are particularly vulnerable to disturbance (e.g. large fish, marine mammals, seabirds and turtles), but also more about the environments they inhabit.

Challenges when Tracking Marine Animals

Many marine animals have incredibly large ranges, travelling 1000s of kilometres. A huge advantage of biologging technologies is the ability to track an individual remotely throughout its range. For animals that dive, information on sub-surface behaviour can be obtained too. This information can then be retrieved when an animal returns to a set location. If this isn’t possible (e.g. individuals that make trips that are too long or die at sea), carefully constructed summaries can be relayed via satellite. This option provides information in real time, which can be very useful for researchers.

Tracks of juvenile southern elephant seals. Red tracks are individuals that returned to their natal colony. Grey are those individuals whose information would have been lost had it not been transmitted via the Argos satellite system.

Tracks of juvenile southern elephant seals. Red tracks are individuals that returned to their natal colony. Grey are those individuals whose information would have been lost had it not been transmitted via the Argos satellite system.

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