New Zealand has only two native land mammals, and they are both bats – the long-tailed bat (Chalinolobus tuberculatus) and the lesser short-tailed bat (Mystacina tuberculata). They have bodies the size of a person’s thumb (5–6 centimetres from nose to tail) and a wingspan of nearly 30 centimetres. The Māori name for both species is pekapeka.
Greater short-tailed bat
New Zealand was recently home to a third species, the greater short-tailed bat (Mystacina robusta). It disappeared from the main islands of New Zealand soon after the Polynesian rat arrived, about 750 years ago. From 1840 until the 1960s the greater short-tailed bat was confined to Big South Cape Island and Solomon Island, off the coast of Stewart Island. These rat-free islands were a refuge for birds, bats and insects that had disappeared from the main islands. However, the arrival of ship rats on Big South Cape and Solomon islands some time in the 1950s or early 1960s was devastating for animals and plants alike. Greater short-tailed bats have not been seen alive since 1967. The species is considered extinct.
Flight and echolocation
Bats are the only mammals capable of sustained flight, thanks to transparent wing membranes supported by extended finger bones. Both New Zealand species are skilled fliers. Lesser short-tailed bats have been timed at speeds of up to 60 kilometres per hour.
Like most bat species, New Zealand’s bats rely on echolocation for foraging and navigation. They emit rapid pulses of high-frequency sounds and detect the echoes from objects nearby. Most of the sounds they make are above the level of human hearing.
Time of activity
The lesser short-tails are nocturnal, flying well after dusk. Long-tailed bats are active both at dusk, and into the night.
Bats are mammals and give birth to live young. Mating occurs in late summer, but there is a delay before pregnancy begins in spring. After a pregnancy of six to eight weeks, New Zealand’s bats give birth around December or January to one naked, blind pup, about a quarter of the mother’s size.
Pups are born in a communal maternity roost, usually a large cavity in an old tree, and they are carried to a new nursery roost each night by their mothers. The mothers return to feed them several times during the night. By four or five weeks of age the pups are covered in fur, their eyes are open and they can fly. It is not known whether they continue to be fed by their mothers once they start flying.
Bats are generally long-lived. The life-span of New Zealand bats has not been determined, but long-tailed bats that have been banded are known to live more than 11 years, and short-tailed bats at least seven years. It is possible that both species could live for 30 years.
Torpor and winter hibernation
Bats can enter a state of torpor where they become motionless and their body temperature drops to a level close to that of their surroundings. This strategy helps bats conserve energy in unfavourable conditions. Long periods of torpor extending into weeks or months are known as hibernation. During winter both New Zealand species hibernate. Winter hibernation is usually made up of periods of torpor lasting for 6–10 days, with bouts of activity that may last for a few hours or a few days.