New Zealand Journal of Ecology (1996) 20(2): 271- 275

Calibration of tunnel tracking rates to estimate relative abundance of ship rats (Rattus rattus) and mice (Mus musculus) in a New Zealand forest

Research Article
K. P. Brown 1,2
H. Moller 1,2
J. Innes 3
N. Alterio 1,2
  1. Zoology Department, University of Otago, P.O. Box 56, Dunedin, New Zealand
  2. New Zealand and Ecosystem Consultants, P.O. Box 6161, Dunedin, New Zealand
  3. Manaaki Whenua - Landcare Research, Private Bag 3127, Hamilton, New Zealand

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 ha(-1) (6.5-7.8 rats ha(-1), 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.