Field voles are one of the most numerous British mammals and because they are prolific breeders, populations in a favourable habitat often increase to number in their thousands - a vole plague. When this happens, competition for space and food and heightened aggression leads to less successful breeding, with the result that the population rapidly declines. The fluctuations in populations usually occur in 3 -5 year cycles. Some predator populations also increase as the vole populations increase. For example, field voles are the main food of barn owls, forming 90 percent of their diet. A shortage of voles has an effect on the number of young barn owls reared.
Other predators include foxes, stoats, weasels, kestrels and snakes.Read More: Field Voles and humans