28 February 2022
Long-tailed bats, or Pekapeka-tou-roa, are as small as your thumb, the wingspan of your hand and weigh the same as a $2 coin. They live throughout New Zealand and are in serious trouble from habitat loss and introduced predators.
Over summer Council staff put up four bat recorders at Waingake. They recorded 455 passes (where an individual bat passes the detector) across all sites, which indicates the existence of long-tailed bats at Waingake.
The four AR4 Acoustic and Bat Recorders bought by Council were developed by the Department of Conservation (DoC) as a user-friendly, lightweight and weatherproof way to detect bats.
At Waingake, two of Council's recorders were placed in open forestry cutover (close to waterways and the waterworks bush reserve), one was placed at the margin of the remaining standing pine block and the fourth was placed inside the waterworks bush reserve, just off Tarewa Road.
The data showed long-tailed bats were recorded at all four locations over several nights. This underpins Council's long-term commitment to sustained pest control in the wider Waingake area, which will offer some protection to this existing population and enable it to grow.
Bats are long-lived and breed slowly, meaning any increases in bat numbers may take up to 15 years to detect.
The long-tailed bat belongs to a more widespread family and is closely related to five other species of wattled or lobe-lipped bats in Australia and elsewhere. The North Island and South Island long-tailed bat was confirmed in 2018 as one species. It has the highest threat ranking of ‘nationally critical’.
Long-tailed bats are widely distributed throughout New Zealand. They are more commonly seen than short-tailed bats as they fly at dusk along forest edges using echolocation calls to hunt moths, mosquitoes, and other insects.
Long-tailed bat facts;
- Long-tailed bats are smaller than the short-tailed bat, chestnut brown in colour, have small ears and weigh eight to 11 grams
- They are believed to produce only one offspring a year
- The bat's echolocation calls include a relatively low-frequency component that can be heard by some people
- It can fly at 60km per hour and has a very large home range (100 km2)
- An aerial insectivore, it feeds on small moths, midges, mosquitoes and beetles.
Causes of decline are combinations of:
- Clearance and logging of lowland forests
- Cutting of old-age trees for firewood
- Predation by introduced animals such as cats, possums, rats, and stoats
- Exclusion of bats from roosts by introduced mammals, birds, wasps, and human interference.
Long-tailed bats (Chalinolobus tuberculatus) were first recorded in Waingake waterworks bush in a single survey carried out by the Department of Conservation in 2016. The Pest Animal Management Plan for Waingake Waterworks Bush (prepared for Council by Wildlands in 2019), recommended that the survey work be repeated as part of a wider monitoring programme.
Deploying automatic bat detectors to survey for bats provides an index of bat activity over time. It is recommended that bat monitoring should take place in summer during fine weather where night time temperature is at least 10 degC. Best practice dictates that detectors should be placed at randomly selected points approximately one kilometre apart, in likely foraging paths. They should be at least 200 metres away from the forest edge. If possible, detectors should be set to record from sunset to sunrise for several consecutive nights. (Latham et al. 2017)
The bat detectors used for the 2016 survey at Waingake were the property of the Department of Conservation (DoC). Council staff again borrowed these recorder units in early 2020 in an attempt to repeat the survey. Unfortunately on that occasion, the recorders malfunctioned and no data was captured.