PEKAPEK

Forest and Bird, Issue 265, 1 August 1992, Page 21

PEKAPEK

New Zealand’ secretive bats At one time there were four bat species in New Zealand. Today only two survive. Yet, despite their unique status as this country’s only land-living native mammals, very little is known about what they do and even whether they are endangered. TIM HIGHAM reports on how some of the mysteries are being unravelled.

USK in Fiordland’s Eglinton Valley, even in late February, brings a chill to the air. The wind dies away and with it our conversation. We prefer momentarily the company of high, dark hills and paling sky. Then silhouetted against the last of the day’s light is what we came to observe. Suddenly close by, it flutters like a magnificent butterfly above the stream.

Darting, changing direction and speed in strange, staggered flight, it forages on mayflies hatching from the water. The object of our curiosity is a longtailed bat which, along with its lesser short-tailed cousin, is New Zealand’s only native terrestrial mammal. Surprisingly little is known about bats by the general public. Their habits of being active only at night and of covering large territories using multiple roost sites, have not helped the very few people who

have attempted to study them. Of the four species known to have existed, the long-tailed bat is the most common and is widely distributed through the North and South Islands, Stewart Island, Little Barrier and Great Barrier Islands and Kapiti Island. The lesser short-tailed bat is found only in a few scattered North Island forest sites, North-West Nelson Forest Park, and on Little Barrier Island and Codfish Island. The greater short-tailed bat became

*BATS* extinct in about 1965 when ship rats reached its last refuge on Big South Cape and Solomon Islands off south-western Stewart Island. Recently a fourth, as-yet-unnamed species, identified from sub-fossil and skeletal remains, has been added to the list. From its teeth, skull and foot bones it appears it was the largest of the shorttailed bats and had evolved furthest along the path toward a terrestrial habit. It probably became extinct some hundreds of years ago after the arrival of the Maori and their Polynesian rat, kiore. Maori did not differentiate between bat species and called all of them "pekapeka"’, a diminutive of "peka’’, the name given to the fruit bat of their Pacific island homeland. In an ancient Maori proverb bats were associated with the mythical, night flying bird hokioi and were meant to foretell death or disaster. ~ UCH of our current knowledge /| about bats is due to the work of | : Mike Daniel, a recently-retired DSIR ecologist, whose research a or 20 years. During the late 1970s and early 1980s his work on bat distributions was helped by the public

who sent in nearly 300 responses to appeals for information about sightings. For the last 11 years Daniel has conducted the only long-term behavioural studies on bats — on the lesser short-tailed populations on Codfish Island and in Omahuta kauri forest in Northland. On Codfish Island he has used mist nets to capture bats and then attached tiny transmitters weighing only one and a half grams (but ten percent of the weight of the animals). He found that the bats flew 30 to 40 kilometres in a night and alternated roost sights between favoured trees. Also useful in his research were ultrasonic bat detectors which pick up the sounds — inaudible to humans — emitted by bats during echolocation. Infra-red night-vision telescopes and binoculars, the latter used by the British in the Falklands War, have enabled him to observe bat behaviour. Lesser shorttailed bats burrow into leaf litter and humus in search of food and can excavate tunnels for roost sites in rotting trees. Such behaviour is unique among bats, and the species has evolved wings which can be tightly folded into a protective pouch formed by leathery wing membranes and a skin flap on the side of the body — adaptations which make it much

easier to hunt on the forest floor. Daniel has found that despite their relatively heavy feet, lesser short-tailed bats still retain impressive powers of flight. On Codfish Island he has watched them flying at night through tightly-packed forest at around 20 km an hour. Even in rain they are able to receive the echoes of rapid pulses of high frequency sound emitted from the mouth, and cruise comfortably through the maze of twigs and branches to catch flying insects. Over the past five years Daniel has discovered that the Codfish Island bats are lek breeding, a courtship behaviour shared among bats with only two African species. Like Codfish Island’s other lek breeders, the kakapo, male bats gather

at display sites which females visit for mating. The lesser short-tailed bat feeds on a variety of foods: fruit, insects, meat and nectar. Muttonbirders on the islands off Stewart Island used to smoke bats out of caves and kill them because they occasionally chewed on the fat and meat of hanging muttonbird carcasses. This omnivorous feeding behaviour enables the short-tailed bat to remain active all year round, unlike the strictly insectivorous long-tailed species which hibernates in cooler regions over winter, when insects are less active. PT \ HE ANCESTORS of the long- ; tailed bat were probably blow-ins from Australia. Daniel says it is » surprising that New Zealand has one bat derived from Australian stock, considering that country’s 60-odd species and the prevailing westerly winds.

Bat genealogy

Bats form the order Chiroptera (from the Greek "hand-wing"). With almost 1,000 species they are the second largest order of mammals after rodents. There are two sub-orders: Megachiroptera (fruit bats or flying foxes) 1 family, 173 species in tropical and sub-tropical areas worldwide. Navigate by sight alone and eat nectar and fruit. None in New Zealand. Microchiroptera 18 families, 2 of them in New Zealand. r Family Vespertilionidae 320 species. Genus Chalinolobus 6 species in the west Pacific region including the New Zealand longtailed bat which is probably descended from bat(s) blown across the Tasman Sea about a million years ago. Family Mystacinidae (short-tailed bats). Endemic to New Zealand. Only 1 living species, the lesser short-tailed bat, Mystacina tuberculata, and 2 extinct species. These bats are thought to be distantly related to three families of South American and Central American bats. They possibly arrived in New Zealand via a forested Antarctica about 35 million years ago. there are 16 other families.

Despite the regular appearance of Australian birds, butterflies and moths only one vagrant bat has been reported in New Zealand in European times: a little red flying fox, found electrocuted under powerlines after a storm in Hamilton about 1928. Daniel believes his studies of skeletal and subfossil remains from around the country show there have been only four bat species in New Zealand since the last Ice Age, about 15,000 years ago. Surprisingly, despite being the more common of the two extant species, there have been no long-term studies carried out on long-tailed bats. Even the location and scientific study of a nursery roost would be a first. In Fiordland’s Eglinton Valley, where bats are relatively abundant, Department of Conservation scientist Colin O’Donnell aims to rectify this situation. He plans to sample different habitat types through the year to establish their seasonal use and importance. By measuring temperature, wind strength, cloud cover and moonlight each night he hopes to build up a picture of factors effecting activity. O’Donnell is also trying out a bat detector. He hopes to be able to correlate the ultrasonic clicks of the bats with population density.

Long-tailed bats have been reported in native forest from sea level to the bushline, usually near the bush edge. Occasionally they are seen in exotic pine forest, shelter belts and buildings. They feed along forest margins and over farmland, streams and lakes, solely on small aerial insects. They are the bat species most likely to be seen by the public and can be confused with large puriri moths, welcome swallows or fantails because of their rapid, darting flight. oC 1s now starting to move on the problems of bat conservation. The department has recently contracted Daniel to produce a draft recovery plan.