New Zealand has two species of bats: the long-tailed bat (Chalinolobus tuberculatus) and the lesser short-tailed bat (Mystacina tuberculata). A third species, the greater short-tailed bat (Mystacina robusta) is considered extinct, having last been observed in 1967.
Both extant species are threatened and rarely seen. The short-tailed bat likes to live deep in the interior of bush and is highly localised in its distribution. It has never been confirmed in the Kaimai ranges. The long-tailed bat is more widespread and prefers the edges of bush. It has been occasionally observed at various sites in the Kaimai, and the Project was naturally very keen to find out if either species was present at Aongatete.
A number of automatic bat monitors (ABMs) were kindly lent to us by the Bay of Plenty Regional Council and deployed by AFP’s Chairperson, James Denyer. Placed at fixed locations in the forest, the monitors automatically record the ultrasonic calls that bats make as spectrograms. These spectrograms can then be analysed by a computer program and the presence of bats confirmed.
The “signature” of each bat species is different, so the recordings allow for species identification. However, the ABMs also record other ultrasonic noises. There are usually large numbers of insect and rodent spectrograms to sift through, as well as sounds made by wind and rain. Fortunately each of these types of spectrograms look very different to those of bats, so are easily discarded.
At Aongatete, some of the ABMs were deployed deep in the forest in places potentially attractive to short-tailed bats. Others were placed on the edges to find long-tailed bats. After a couple of weeks, the ABMs were retrieved and analysed. The exciting result was that the presence of long-tailed bats was confirmed at the edge of the forest above the kohanga.
It is also possible to detect bats in real-time with the use of a hand held bat detector. These devices ingeniously convert the ultrasonic noises of bats into audible sounds that humans can hear. Again, the species can be discerned by using different settings on the machine. Subsequenty to the initial discovery of bats, a group of volunteers traipsed slowly round the kohanga paddock at dusk and were fortunate to hear a pass from a long-tailed bat.
It is hoped that further monitoring will take place, and perhaps we might even discover short-tailed bats. This would be wonderful news as the short-tailed bat plays a key role in the pollination and reproduction of Dactylanthus taylorii, the wood rose, which is being re-established in the forest at Aongatete.