Keeping track of the stoats

Forest and Bird, Issue 281, 1 August 1996, Page 25

Keeping track of the stoats

/ =") ELIABLE MEASURES are needed ~ to assess how effective stoat ‘"Acontrol operations have been. Conservation managers often ask whether stoats are present in an area, whether they are present in sufficient numbers to threaten a particular species or wildlife community, and if sufficient have been killed after a control operation to reduce or remove that threat. Stoats were first radio-tracked in New Zealand by Elaine Murphy and John Dowding in 1990. Working in the Eglinton Valley, one of their first challenges was to come up with a radio-transmitter package that would stay on a stoat. By the end of the two-year study they had one, but it took considerable time (and a lot of frustration) to develop. The study gained information on stoat home ranges, movement patterns and eating habitats. One of their main findings

was that stoats were very mobile and covered large distances quickly. They regularly had stoats moving more than two kilometres in three to four hours, just while foraging in their normal — average about 120 hectares — home range. One juvenile female travelled 65 kilometres in four weeks. As part of the Westpac sponsorship supporting DoC’s Mohua Recovery Programme, the use of footprint tracking tunnels to work out whether stoats are present in mohua areas, was investigated in 1994, These tracking tunnels provide a technique which has potential to assist in all levels of stoat population assessment. While the ultimate measure of the success of a control operation is significantly improved productivity and survival of the threatened species being protected, such detailed measures are not always possible.

Information on how much the stoat tracking rates vary (for example, how many footprints you record in an area per week, and how this changes over time), and whether footprints decline significantly or disappear after a stoat control operation, is needed. To record the stoat footprints we are using special tracking tunnels. The tunnels contain a foam pad treated with a special concoction of chemicals, and treated papers are placed either side of this chemical ink pad. When a stoat runs through the tunnel its footprints are recorded permanently on paper. Baseline information on tracking rates was gathered from November 1994 and February 1995 and the tunnels were useful for showing if stoats were present in the study areas. Some declines were recorded after trapping and poisoning experiments. No footprints were found in one study area after all radio-tracked stoats were known to have been killed. After one week of poisoning and the death of half the radiotracked stoats, the tracking rate in that area was also halved. Tracking also showed that at least one stoat remained in an area where we conducted Fenn trapping once trapping had ceased.