Both species of New Zealand bat are found in native forests from sea level to the treeline. Their natural habitat is mature forest with many large hollow trees. These trees are used as roosting sites by the bats, either singly or in colonies of up to 100 individuals. Long-tailed bats also roost in caves at times, and some colonies have become established in mature pine (Pinus radiata) forests.
Lesser short-tailed bats and long-tailed bats were once numerous and widespread in forested regions. The most conservative estimate for the pre-human population of lesser short-tailed bats in the central North Island is 12.5 million.
Human settlement had a drastic effect on the number of bats. Causes for their decline include:
- loss of habitats through clearance and logging of lowland forests
- introduction of new predators
- competition for roost sites from introduced mammals, birds and wasps
- human interference and disturbance of roost sites.
Rats, stoats and cats are key predators, particularly during winter when roosting bats are immobilised by torpor for long periods. The short-tailed bat’s ground-feeding habit also makes it an easy target.
By 2005, short-tailed bats were restricted to 13 populations:
- two large ones on Little Barrier Island (in the Hauraki Gulf) and Whenua Hou/Codfish Island (off Stewart Island)
- seven in the central North Island, with about 40,000 bats
- four small, isolated populations (two in the North Island, two in the South Island).
Long-tailed bats are found in scattered populations, from the north of the North Island through to the western South Island and south to Halfmoon Bay on Stewart Island. They are also found on Great Barrier, Little Barrier and Kapiti islands. They survived in some cities until the 1920s and 1930s.
Although both species are under threat, the lesser short-tailed bat is ecologically more precious as it is the only remaining species within its family.
Department of Conservation (DOC) programmes focus on protecting roosting sites, enhancing habitats and controlling predators, as well as education. DOC has a recovery programme which aims to ensure the survival of bats, and to establish new populations within their historical range.
Lesser short-tailed bats are important pollinators for a number of indigenous forest plants, including kiekie, pōhutukawa, wood rose and perching lilies. While none of these plants depends solely on bats for pollination, bats are often more effective at it than birds. Lesser short-tailed bats also spread plant seed in their droppings.
Captive husbandry of bats is possible, and captive breeding is being attempted. Short-tailed bat pups bred in captivity were successfully moved to predator-free Kapiti Island in 2005.
Live bats are protected by the Wildlife Act 1953 and must not be disturbed. If any dead bats are found, their bodies should be sent to a major museum or the nearest DOC office, with information about where, when, and by whom they were collected.