Population cycles of small rodents are caused by specialist predators: or are they?

Predation by specialist mammalian predators has been hypothesized to be the primary cause of multi-annual density fluctuations (‘population cycles’) in voles. Using a series of replicated field experiments, Isla Graham and Xavier Lambin have now shown that specialist mammalian predators are neither necessary nor sufficient to drive field vole Microtus agrestis population cycles. These findings conclusively contradict the specialist predator hypothesis. The search for the mechanisms underlying the spectacular dynamics of cyclic vole populations must, therefore, continue.