CALIBRATION OF TUNNEL TRACKING RATES TO ESTIMATE RELATIVE ABUNDANCE OF SHIP RATS (RATTUS RATTUS) AND MICE (MUS MUSCULUS) IN A NEW ZEALAND FOREST

Abstract

Ship rat (Rattus rattus) and mouse (Mus musculus) density and habitat use were estimated by snap trapping and tracking tunnels at Kaharoa in central North Island, New Zealand. Eighty-one ship rats were caught in an effective trapping area of 12.4 ha. Extinction trapping gave an estimated density of 6.7 rats ha1 (6.5-7.8 rats ha1, 95% confidence intervals). A linear relationship existed between ship rat trapping and tracking rates. Estimating the density of mice was impossible because trapping rates increased rather than decreased during the experiment. Comparisons of density from tracking and trapping rates of mice may be confounded by interference by rats, but this requires further investigation.