Throughout the world rats have invaded islands with devastating consequences for local fauna, particularly birds, mammals and reptiles. Recently, rats have been eradicated from a number of islands in an effort to restore populations of native animals. However, rats do more than just kills animals: they also eat plant parts (seeds, seedlings, fruit and bark) and radically change the vegetation. Furthermore, many of the islands invaded by rats also served as nesting grounds for large colonies of seabirds, which themselves had large effects on the vegetation and soils (by digging burrows in which to lay their eggs). This project has two goals. First, we will examine how rats affect the vegetation and soils, and how much of this is due to changes in seabird populations. Second, we will evaluate to what extent islands recover from rat effects after rats are eradicated, and whether this depends seabird population sizes. We will do this by comparing three groups of islands located off the coast of New Zealand: one which has never had rats, one which has rats, and one from which rats have been removed during the past decade. If vegetation and soils fail to recover (or take a long time to recover) following the eradication of rats, then efforts to bring back native animal populations may not be successful without additional restoration work. The results of this work will give a better understanding of the effects rats have and how to reverse them on islands everywhere.
