- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Selfish Sheep Seek the Center
23 July 2012 5:08 pm
To escape a hungry wolf, a sheep doesn't have to outrun the wolf, just the other sheep in its flock. Many researchers think that such selfish behavior, not cooperation for the benefit of the whole crowd, shapes the movements of groups of animals. But the decades-old "selfish herd theory" has been hard to back up with data. Now, a detailed analysis of how a flock of sheep moves to avoid a sheepdog has found that the theory holds true. Each sheep heads to safety in the center of the flock, rather than running directly away from the dog.
"It's really difficult to measure 2D spatial information on large animals in the wild," says biologist Theodore Stankowich of the University of Massachusetts, Amherst, who was not involved in the new work. "They've taken advantage of a unique opportunity to work with the sheep to answer these types of questions in a controlled environment."
Studies on seals, crabs, and pigeons have shown that those animals seem to herd for selfish reasons, but the data have often been crude. Biologist Andrew King and colleagues at the Royal Veterinary College of the University of London attached GPS backpacks to 46 sheep and to a trained Australian Kelpie dog. When they released the dog to herd the sheep, they recorded the location of each animal every second. Then, they analyzed the data to determine what factors influenced each sheep's path. The movements of the sheep, the researchers reveal today online in Current Biology, could be best predicted by the center of the flock. Rather than run in a line away from the dog, scatter in all directions, or follow their nearest neighbors, the sheep all hurried toward the flock's center. The sheep began to converge when the dog was 70 meters away. Even as the flock as a whole moved, each sheep continuously competed to be as near the middle as possible.
"The fact that they're running toward the center reduces the chances of their being on the edge and being picked off by a predator," says King. It's a selfish behavior since each sheep puts the animals at the fringes of the flock at risk in order to save itself.
The new observation helps back up hypotheses on the evolutionary pressures that have encouraged animals to group. In addition, further work could reveal how herding behaviors change when sheep are infected with neurodegenerative diseases such as scrapie, which kills sheep and can quickly spread throughout a flock if infected animals aren't quarantined. The results could lead to ways to detect infections earlier through behavioral monitoring, says King.
"These methods are an advance on previous efforts," says Stankowich. "I'd like to see the same technique applied to other large mammals." Even if sheep herd for selfish protection, the findings don't necessarily hold true for all animals.
And trained sheepdogs may not be the best mimic of a dangerous predator, King acknowledges. "It could be a downgraded level of threat, because it's something the sheep have experienced before," he says. The animals' response to a wolf, for example, could be different.