density estimation

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

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.

Distance sampling techniques compared for a New Zealand endemic passerine (Philesturnus carunculatus rufusater)

The effectiveness of line- and point-transect distance sampling methods was compared for estimating the density of a conspicuous endemic passerine, the North Island saddleback Philesturnus carunculatus rufusater, in two forest habitats on Tiritiri Matangi Island, Hauraki Gulf, New Zealand. The reference population abundance in each habitat was calculated through an intensive capture, colour-banding, and resighting effort.

Estimating density of ship rats in New Zealand forests by capture- mark-recapture trapping

We developed a capture-mark-recapture protocol for measuring the population density (D) of ship rats (Rattus rattus) in forest. Either mesh cage traps or Elliott box traps were set at each of six sites (48 traps per site for 5 nights) in the Orongorongo Valley on two occasions in autumn 2003. Cage traps only were set at three sites in autumn 2004. Rats were caught much more readily in cage traps than in Elliott traps and none were recaptured in Elliott traps. Additional food, bedding and trap covers reduced mortality and interference with traps.