Costs and benefits for biodiversity following rat and cat eradication on Te Hauturu-o-Toi/Little Barrier Island

Abstract

Considerable benefits can be achieved for indigenous biodiversity when invasive vertebrates are removed from islands. In New Zealand, two logistically challenging eradications were undertaken, one to remove cats (Felis catus) and the other Pacific rats (Rattus exulans) from Te Hauturu-o-Toi/Little Barrier Island (Hauturu). Here we document the short and long-term impacts of these interventions on the biodiversity of Hauturu. We also assess the extent to which predicted outcomes were reflected in the measured responses for a wide range of species. Short-term impacts of the eradication program encompassed individual mortality for some native species but no measurable impact to populations. Our findings are based on research and monitoring completed on the island from 1962 to the present. We review published and unpublished studies, but also present new data that illustrate changes following rat and cat removal.