Bats in South Canterbury

Forest and Bird, Issue 293, 1 August 1999, Page 45

Bats in South Canterbury

—Ines Stager.

embers of Ashburton and South Canterbury Forest and Bird have joined the hunt for long-tailed bats begun last year by Waikato members. The Department of Conservation has initiated a national monitoring programme for long-tailed bats, focussing on populations at the Eglinton Valley (Fiordland), Hanging Rock (near Geraldine) and Te Kuiti. Naturalists first noted declines around the turn of the century and today they have disappeared from many of their old haunts. The primary aim of the current monitoring programme is to assess the size of these three populations and to determine whether they are stable or declining, and the factors relating to those population trends. Historically, long-tailed bats were

much more widespread than they are today. Along with short-tailed bats, they are our only native land mammals and are unobtrusive and easily overlooked by most people. Weighing in at only 10 grammes and with a total wingspan of about 20 centimetres they are as acrobatic as the fantail, but travel much greater distances, at speeds of up to 60 kilometres an hour, as they forage for insects along forest margins and over the canopy. Their nocturnal habits make them difficult to observe, but as Forest and Bird helpers have recently found out, there is more than one way to track them down. First and foremost in any batresearcher’s tool kit is a bat detector — a small black box that converts high frequency bat calls into a sound that humans can hear.

Also important in the kit are several harp traps — large rectangular aluminium frames strung with vertical nylon fishing line with a catching bag underneath. Echolocation signals from the bat are confused by the vertical strings, the bat flies into them and drops into the collecting bag where they are collected the next morning and banded, weighed, measured, aged and sexed. Some are fitted with tiny radio transmitters weighing only 0.8 gramme, with another important tool in the research kit, being an aerial and receiver. Bats can then be followed around at night, and tracked to their roosts the next day. Forest and Bird members from Mayfield, Pleasant Point, Geraldine, and Ashburton districts have recently assisted with bat

counts using this equipment. They undertook walking surveys around roads at each site to assess bat activity in the surrounding landscape. Most members were happy to spend two to three hours each night surveying and were rewarded by seeing bats close up in the hand. Some enthusiastic Forest and Bird members were determined not to get any sleep at all and helped track bats during their nocturnal wanderings. Such work helps gather information about how many bats there are, and what habitat they are using for foraging and roosting. Ongoing monitoring will allow population trends to be assessed and provide information necessary to manage any threats to these and other populations of

long-tailed bats.