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GPS backpacks reveal sheep flocking strategy

24 July 2012

UK researchers have shown for the first time that instead of fleeing randomly when faced with danger, sheep head straight for the centre of the flock.

Understanding this behaviour in healthy animals may help researchers understand the breakdown in social behaviours caused by neurological disorders in sheep, as well as those in humans, such as Huntington's disease.

Sheep wearing the GPS backpacks

The findings support a 40-year-old idea put forward by evolutionary biologist Bill Hamilton. He suggested that creatures as different as insects, fish and cattle all react to danger by moving towards the middle of their respective swarms, schools or herds.

"Scientists agree that flocking behaviour has evolved in response to the risk of being attacked by predators. The idea is that being part of a tight-knit group not only increases the chances that you might spot a predator, but decreases the chance that you are the one the predator goes for when it attacks," explains Dr Andrew King from the Royal Veterinary College (RVC), lead author of the study, published in Current Biology.

Scientists call this the selfish herd theory - individuals benefit from being in a herd, because they can control where they are relative to their group-mates and any potential predator. This ends up lowering the likelihood of being grabbed by a big, hungry mouth.

But actually demonstrating this has thwarted many scientists, both because predator attacks are unpredictable and it's difficult to track individuals in real time.

Dr King and colleagues from RVC, the University of Cambridge and University College London (UCL) got around this problem by fitting 46 sheep and an Australian Kelpie working dog with mini backpacks loaded with GPS receivers.

They then instructed the dog to herd the sheep towards an open gate on a farm near Adelaide in South Australia. They repeated the exercise twice more, then used the data they collected to calculate exactly where the centre of the flock was, how far the Kelpie was from the middle of the flock, as well as how far each sheep was from the middle of the cluster on a second-by-second basis.

They found that when the dog got within 70 metres of a sheep, the sheep would try to get to the centre of the flock until eventually they were in a tight cluster.

"If we put similar backpacks on insects, fish and other creatures that swarm, shoal or herd, we're confident we'd see similar patterns. But, by using sheep, we could directly test Hamilton's prediction, because we had control of the system we were testing," says Professor Alan Wilson, Head of the Structure & Motion Laboratory at RVC, who co-authored the study.

"Sheep must be attuned to their neighbours' reactions to be able to flock like this. We are now using our approach to understand the breakdown of group behaviours that may occur when sheep are injured, ill, or have diseases. Having an understanding of normal behaviour means that changes in behaviour can be linked to the progress of neurological diseases such as Huntington's disease," says Professor Jenny Morton from the University of Cambridge, co-author of the study.

The study was funded by CHDI Foundation, Inc, a not-for-profit research organisation exclusively dedicated to developing therapies that will slow the progression of Huntington's disease, while Dr King was supported by the Natural Environment Research Council (NERC).

Further information

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Scientists' contact details:

Dr Andrew King (primary contact)
The Royal Veterinary College
Tel: 01707 666988
Mob: 07786 033412

Professor Alan Wilson
The Royal Veterinary College
Tel: 01707 666259

Professor Jenny Morton
University of Cambridge
Tel: 01223 334057

Notes

1. To download images and videos of the sheep being herded by an Australian Kelpie and the research paper visit our FTP site .

2. This press release is based on the paper 'Selfish-herd behaviour of sheep under threat', Andrew J King, Alan M Wilson, Simon D Wilshin, John Lowe, Hamed Haddadi, Stephen Hailes, and A Jennifer Morton, published online in Current Biology on 23 July 2012.

3. Dr King and his colleagues have published a previous study demonstrating that the GPS device harness fitted to the sheep has no effect on their behaviour - 'Data-loggers carried on a harness do not adversely affect sheep locomotion', H Hobbs-Chell, AJ King, H Sharratt, H Haddadi, SR Rudiger, S Hailes, AJ Morton, AM Wilson (2012), Research in Veterinary Science 93: 549-552.

4. The Royal Veterinary College is the UK's first and largest veterinary school and a constituent College of the University of London. In the recent Research Assessment Exercise the RVC ranked as England's best school in the Agriculture, Veterinary & Food Science unit of assessment, for institutions whose research is exclusively veterinary related, with 55% of its submitted academics viewed as producing 'world class' and 'internationally excellent' research. The College provides support for veterinary and related professions through its three referral hospitals, diagnostic services and continuing professional development courses.

5. NERC is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, environmental influences on human health, the genetic make-up of life on earth, and much more. NERC receives around £300m a year from the government's science budget, which it uses to fund research and training in universities and its own research centres.

6. CHDI Foundation, Inc is a privately-funded, not-for-profit, biomedical research organisation that is exclusively dedicated to rapidly discovering and developing therapies that slow the progression of Huntington's disease. As a collaborative enabler, CHDI seeks to bring the right partners together to identify and address critical scientific issues and move drug candidates to clinical evaluation as quickly as possible. Their scientists work closely with a network of more than 600 researchers in academic and industrial laboratories around the world in the pursuit of these novel therapies, providing strategic scientific direction to ensure that their common goals remain in focus.

Press release: 19/12

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