Original URL: http://www.theregister.co.uk/2012/07/24/gps_sheep_study/
GPS-equipped sheep prove herd mentality exists
Woolly thinking helps tight-knit groups of animals to survive
British Boffins from Cambridge, University College London and The Royal Veterinary College have used an Australian farm to research flocking behaviour in herd animals and feel they have validated theories about how herds of animals protect themselves from predators.
Detailed in Current Biology , the team started with the long-held theory that “A major factor in the evolution of flocking behaviour is thought to be predation, whereby larger and/or more cohesive groups are better at detecting predators...” Herds are also thought to be better at responding to predators, as once an individual herd member detects a threat it will alert its herd-mates. All members of a herd were thought to then bunch up, to make it harder for predators to pick a target.
The team found most of those assumptions valid after setting a trained sheep dog on 46 Australian sheep, all of which wore GPS trackers. The sheep “demonstrated classic aggregation and avoidance behaviour” once the dog came within 70 metres, and each individual “moved towards the flock centroid until they were in a tight cluster” as shown in this video  of one test (AVI download).
The resulting tightly-knit (pardon the pun) herd of sheep meant no lone individual could be picked off by a predator, which could explain why so many land and animals gather in groups.
The researchers admit that larger-scale tests are needed to fully validate the theory. ®