Bats on Barrier?

EMMA WATERHOUSE

Are bats on Aotea? Well yes, but very little is known about them. One of New Zealand’s two species is definitely on the island, the long-tailed bat (Chalinolobus tuberculatus). The other, the lesser short-tailed bat (Mystacina tuberculate) has never been recorded on the motu, but was likely here before the arrival of humans.

The long-tailed bat, or pekapeka, was recently reclassified as nationally critical. They inhabit the forest edge, feeding above the canopy, pasture margins, along streams at night, and sometimes in caves. Look out for them flying around at dusk. There are sporadic records of its presence on Aotea, including from Miners Cove (Te Paparahi), although the first island wide survey wasn’t carried out until 2004.

Island-wide bat survey

According to Halema Jameson and associated records, the Department of Conservation carried out island wide bat surveys in 2004 and 2005. The survey targeted the long-tailed bat by walking one kilometre-long transects along the island’s roads (including Kaiarara Forest Road) at night. Bat passes were recorded on a hand-held bat detector. The data shows that long-tailed bats were recorded or seen in Okiwi, Fitzroy, Awana and Kaitoke transects, with the most records from Fitzroy followed by Okiwi. Automatic bat recorders were also placed in Te Paparahi in the Wreck Bay catchment to look for short-tailed bats, but none were detected.

Lesser short-tailed bats on Aotea?

At one time, lesser short-tailed bats are likely to have been common throughout Aotea. They are an important pollinator of the native wood rose (Dactylanthus taylorii), New Zealand’s only fully parasitic plant. Both the wood rose and the lesser short-tailed bat are now at risk of extinction.

Short tailed bats are more likely to be found in larger old growth forest as they roost in large numbers and often use large old hollow trees. No comprehensive survey for short tailed bats on the island appears to have been completed - but if they do hold on in Aotea’s forests, a good place to look might be Te Paparahi.

New Zealand’s Bat Species

New Zealand has two living species of bats, the lesser short-tailed bat and the long tailed bat; and one species which is thought to be extinct (greater short-tailed bat (Mystacina robusta)). Pekepeke (bats) have been around in New Zealand for a long time - for long-tailed bats over a million years ago when their ancestors came across from Australia. Short-tails were already ancient residents.

Bats are New Zealand’s only species of land mammal, using echolocation to find food and for navigation. These tiny animals emit rapid pulses of high-frequency sound, detecting sound as it bounces back from nearby objects. We are unlikely to hear bats, as most of their sounds are above the level of human hearing. The natural habitat of bats is mature forest with many large hollow trees which are used as roosting sites, either alone or in colonies of up to 100. Bats are thought to live for up to 30 years and are known to hibernate, entering periods of torpor for up to 10 days, interspersed with periods of activity.

Lesser short-tailed bats

This ancient species endemic to New Zealand is found in a few scattered sites around the country. Three subspecies are recognised:

• Northern lesser short-tailed bat (At risk - recovering) - Northland and Hauturu Little Barrier

• Central lesser short-tailed bat (Nationally vulnerable) - Northland, central North Island

• Southern lesser short-tailed bat (At risk - declining) - Whenua Hou/Codfish and Fiordland.

Weighing in at between 12 and 15 grams, these bats have adapted to hunting on the ground for insects, fruit, and pollen. They are thought to be ‘lek’ breeders, with male bats congregating to compete for females by ‘singing’. As ground feeders, they are vulnerable to rats, cats and stoats.

Long-tailed bat

This species is nationally critical and is found in areas of the North and South Island, Stewart Island, Hauturu Little Barrier, Aotea Great Barrier and Kapiti Island. Smaller than the short tailed bat, this species weighs in up to 11 grams.

Long-tailed bats catch prey in the air, feeding on small moths, midges, mosquitoes and beetles. The species forms complex social groups, frequently switching between roosting alone and roosting with a colony, often staying only one night at one location. Long-tailed bats are more commonly seen than short-tailed bats as they fly at dusk along forest edges. They can fly at 60 km/hour and have a home range of up to 100 km2 . Have you seen any?

Acknowledgments:

Thanks to Halema Jamison and Department of Conservation for providing information on the Aotea bat survey and past sightings.

References:

1. Halema Jameson, personal communication.

2. Armitage, Don. The Woodrose and Short Tailed Bats. https://sites.google.com/a/aotea.org/donarmitage/Home/great-barrier-island-fauna--flora/ bats. Accessed 29 November 2020.\

3. Te Ara. The Encyclopedia of New Zealand. Bats. https://teara.govt.nz/en/bats. Accessed 29 November 2020.

4. Department of Conservation. Bats/pekapeka. https://www.doc.govt.nz/nature/native-animals/batspekapeka/. Accessed 29 November 2020.