Short-tailed Bats Found in Tararua Ranges

Forest and Bird, Issue 297, 1 August 2000, Page 10

Short-tailed Bats Found in Tararua Ranges

—Alina Arkins

tiny population of short-tailed bats has been discovered in the Tararua Ranges north of Wellington. The threatened bats were previously known only from Omahuta Forest in Northland, Rangataua Forest on the slopes of Mount Ruapehu, and from Whenua Hou/Codfish Island off Stewart Island. In March this year, four shorttailed bats were caught on the eastern side of the Tararua Forest Park, identifying this area for the first time as containing a population of this species. Since the summer of 1996-97, the Wellington conservancy of the Department of Conservation has been surveying areas of the Tararua Forest Park for our two native bat species. Each season, echo-location calls of long-tailed bats were recorded at several areas on the custom-designed ‘automatic bat monitors’ In February 1999, however, contractors reported that echo-loca-tion calls had been recorded in

the Waiohine Valley at 28 kHz, the frequency used to survey for the short-tailed bat. Following up on this discovery, DoC decided that the 19992000 survey would focus entirely on short-tailed bats, with contractors returning to the area in early December to find whether the bats were still there. On con-

firming this, the survey then proceeded to cover adjacent areas in the valley in an effort to

find sites with higher bat activity. The plan was to set up mistnets and try to catch some bats if suitable sites could be found. In early March this year, mistnets were set up at two areas in the valley, and four short-tailed bats were finally caught after several unsuccessful nights. The bats were weighed, measured, and aged, and had samples taken for dietary and genetic analysis. Tiny radio transmitters, each weighing less than a gram, were attached to their backs just before they were released. By attaching transmitters, it

was hoped the bats would lead researchers to their communal roosts, so infrared video cameras could be set up to count the animals as they flew out in the evening. In this way DoC could estimate the size of the bat population in the area. This process has been successfully carried out in recent years in other parts of New Zealand where short-tailed bats occur. The four bats caught

in the Tararua Ranges were found to be roosting solitarily, however. DoC plans to return researchers to the area early next season for another attempt.

The largest mainland population of short-tailed bats is in the Rangataua Forest on the slopes of Mount Ruapehu (see Forest & Bird, May 1998).