Hiking St. Cuthbert’s Way recently, we were reminded of how sheep run together when you come near them. Each one is determined not to be an outlier that the wolf might pick off. Safety in numbers.

It’s interesting to note that the simplest model of this behavior shows no advantage to the flock. The hungry wolf is going to take exactly one sheep, regardless of whether they’re huddled together or sparsely scattered. Thus flocking together does not improve the mean risk of death for the sheep, averaged over the flock, though it’s a big win for some of the individuals.

So the safety in numbers effect is another example like that paradoxical phenomenon that a population generally doesn’t have many more females than males, even though there could be more offspring if the ratio were ten to one. Evolution optimizes the individual, not the group.

[20 April 2023]