Very little is known about the ecology of New Zealand bats. Although reports of bats since 1930 include all provinces, as well as Little and Great Barrier Islands, Kapiti Island, Stewart Island, and several of its adjacent smaller islands, the species are nowhere abundant. In the North Island most records come from the Rotorua-Waikaremoana and Upper Wanganui River districts, while in the South Island the north-western corner appears to support the highest densities. Generally, bats are seen at forest margins, in cleared areas adjoining forest, or over rivers, lakes, swamps, etc., when these are near forest. The reduction in bat distribution during the last century has paralleled the extensive reduction of forested areas. Both species have failed to colonise urban areas. Most sightings of bats are made on fine, warm nights and, although only one or two individuals are usually seen, some flights of several dozen bats have been observed over water. The flight of both species is characterised by frequent changes of direction. Some records suggest that the short-tailed bat flies later than the long-tailed bat and that its flight is more direct than that of the latter species. The long-tailed bat emerges in the evening about half an hour after sunset. Sometimes short-tailed bats have been captured in dense forest after flying into lanterns or lighted huts. During the day both species may roost in hollow trees or caves. Sometimes individuals are found beneath the curled bark of trees, and there are occasional instances where bats have been disturbed amongst the folds of sacks in old sheds. Usually the number of bats found together is small, but colonies up to about 30 short-tailed bats and several hundred long-tailed bats have been observed. Whether such large colonies are formed only during certain months of the year for reproductive purposes, as is the practice with many bats in other countries, is a question that as yet remains unanswered.
by Peter David Dwyer, M.SC., Lecturer in Zoology, University of New England, Australia.