Rare long-tailed native bats found to be widespread in Tairāwhiti

Gisborne is home to native bats also known as pekapeka.

“This is often a surprise to people,” Ecoworks NZ’s Steve Sawyer says.

“Don’t worry — they aren’t bloodsucking vampire bats or anything that will hurt you or spread disease.

“They are very clean, they eat insects and are the size of a mouse.

“They are a fascinating animal.  Bats are our only native land mammal and have been in New Zealand for an estimated 35 million years. Our bats weigh around 13 grams and can live for 35 years which is an incredible feat for such a small mammal.

“Long-tailed bats are regarded as nationally very rare. Within the Tairāwhiti region long-tailed bats appear to be widespread.  They are a keystone species indicator of ecosystem health. They need clean water streams to drink from and they eat the insects or macro-invertebrates which hatch from our clean stoney-bottomed streams.

“These are the critters you see when you turn over a rock in the river. These insects hatch into flies and our bats then eat them. When we fill our streams with silt and destroy the habitat we destroy the endemic pekapeka too.

“Bats also prefer native trees on our river edge to roost and breed in so together with silted river beds and a loss of native riparian forests our bats potentially face an uphill battle.  Like our long-finned eel they are therefore an indicator of a healthy functioning stream ecosystem.”

The Ecoworks NZ team has been carrying out acoustic monitoring for bats since 2010 across many parts of the region.

“During summer we find bats within most sites that we survey from Wharerata to Motu to Huanui, Mata and the Waimata River. They are found within both native forest and exotic radiata production forest which is associated with native forest areas which generally provide the hollow, cavity-bearing breeding trees for this species.”

Two species of bat have been recorded within Tairāwhiti, the long-tailed bat and the short -tailed bat.

“The short-tailed bat has not been seen within Tairāwhiti for a number of years and we hope a population is still hanging on somewhere within the Raukumara Range. One was found dead on a barbed wire fence at Te Araroa many years ago and short- tailed bats were recorded at East Cape during the 1980s.

“Short-tailed bats are now restricted to only a few mainland sites which receive predator control, and offshore islands which are predator-free such as Hauturu Island (Little Barrier Island). Historically the short-tailed bats pollinated the parasitic dactylanthus or ‘woodrose’ plant which grew on the forest floor. Short-tails spend more time walking on the forest floor compared with the long-tailed bat, making them more susceptible to predators such as cats which are considered a major predator for bats.

“The long-tailed bat spends the day within hollow cavities inside tree stems and branches, particularly rimu, totara and kahikatea and they emerge shortly after dusk. They are easiest to see during the summer months when they are most active. DoC bat ecologists have shown that bats spend a large amount of their time drinking from stream pools. While in flight they will swoop down and drink from the water surface.  Using radio transmitters researchers have confirmed bats travelling over fifteen kilometres in a night to feed or locate a different roost location.”

Recent research using DNA sampling collected from bat droppings has shown long-tailed bats feed mainly on small moths, mayflies, stoneflies, mosquitos and other small flying insects which hatch from rivers, streams and ponds, Mr Sawyer said.

“Clean, stoney-bottomed, good quality stream habitat is vital for this species and their long-term protection. Silt, excessive nutrients from fertilisers and forest slash destroy these macro-invertebrate populations which in turn will impact the bats’ ability to feed. Bats catch these flying insects or ‘macro-invertebrates’ on the wing while in flight using their tails and wings to scoop up their prey.”

The Ecoworks team monitor bats using spectral recorders, thermal imaging cameras and hand-held bat detectors, for a wide range of clients across Tairāwhiti.

“These recorders are positioned at a location which is likely to detect passing bats such as near a stream, a pond or roadway. As bats are flying they are very noisy, emitting ultrasonic clicks which bounce off their prey much like a dolphin uses sonar to locate fish.  As the bat gets closer to its food item it fires a machine gun burst of clicks at 40 kilohertz and zeros in on its prey and catches it. Some moth species have evolved to actually detect these ultrasonic bat clicks and avoid the bat by going into a steep aerial dive to avoid being eaten!

‘The recorders give us a spectrogram, an actual picture of the ultrasonic bat clicks as they fly past the recorder and you can see when the bat has locked on to its target and fires the ultrasonic clicks at the mosquito or moth.

“As humans we cannot hear the bat vocalisations as the frequency is outside our adult hearing range therefore the recorder does this for us, giving us a clear picture of bat calls as they pass by as well as the date, time, location and air temperature. We can determine the species from the call range and shape on the spectrogram.

“We have not detected short-tailed bats within Tairāwhiti since we started this monitoring in 2010.”

A special bat management reserve has been established at Huanui for long-tails which includes pest control and artificial bat roosts installed in native forest, as well as the protection of roost trees within 150 metres of streams.

“At Whinray Reserve near Motu bats are doing well and are protected with high quality predator control to remove rats, stoats, cats and possums which all kill native bats.

“At Motu Scenic Reserve the Te Aitanga a Mahaki taiao team is working with Ecoworks NZ and Motu School to remove predators and protect this ancient and endemic rare species.

“This unique and endangered species can be seen in the evening at several locations within our region at dusk as they emerge from their tree roosts and begin feeding. Motu Scenic Reserve is a good location to see the bats flying above the Motu River as is Pakowhai Road at Muriwai during January and February.