20 years on, bats return to Waikato
They ranged the district 20 years ago, flying up to 19km each night at up to 60kmh.
But no-one had heard or seen the little critters in over two decades until a Waikato ecologist from Manaaki WhenuaLandcare Research got out and looked for them.
Now, a nationally threatened bat species has been discovered in Morrinsville, 32km northeast of Hamilton.
Dr Norman Mason discovered the chestnut brown nocturnal species after he conducted a series of surveys that stemmed from the Covid-19 lockdown.
For many years, there were concerns the local bat population had died out since the last bat survey, 20 years ago, by Dr Kerry Borkin.
‘‘Nobody had looked for them since, there was a worry the population had died out in the meantime,’’ Mason said.
The long-tailed bats are vulnerable to predation and compete for roosting sites (holes in trees) with possums and rats.
Stoats, feral cats and moreporks also add to growing concerns.
Long-tailed bats were common throughout New Zealand in the 1800s, although by 1900-1930 they were becoming scarce in many districts.
In 2018, the North Island long-tailed bat population faced a major decline in numbers since 2012. At the time it was more prone to extinction than kiwi, ko¯ kako and whio, according to the Department of Conservation.
However, the fate of the bat population in Morrinsville defied all odds.
Mason recorded activity at 50 of the 60 sites he monitored.
This included areas along the Piako and Waitoa rivers, the Waitakaruru stream and eastern tributaries of the Waikato River.
Long-tailed bats are smaller than the short-tailed bat, they weigh about 8-11g, have a wingspan of 25 centimetres and are one of New Zealand’s only native land mammals.
Mason’s curiosity into bats started in 2019 with the local school, Te Kura o Waharoa.
They were just about to get into surveying when the lockdown hit.
But it was during this time he used the five acoustic bat monitoring devices he was gifted from the Waikato Regional Council and put them to use.
When lockdown lifted Mason asked farmers around the town if he could put up one of his bat detectors.
The devices record echolocation calls bats make as they fly past and can be left outside for a couple of weeks.
Part of his motivation was to see ‘‘if the remaining bats were using the riparian forest as habitat.’’
Tall forests next to waterways are considered prime bat habitat.
They provide corridors for movement and access to abundant food like flying insects.
‘‘They like trees that have nice big cavities and big trees with dense wood for insulation,’’ Mason said.
‘‘They can be found in different strands of oak trees, or in gum trees in some cases.’’
‘‘Having the trees along the big rivers in the Piako Catchment is really important and it’s a contributing factor to our persistent population.
‘‘They eat a lot of flying insects . . . but mainly they’re really cool, people are fascinated by them.’’
At least one potential roost tree has been identified and surveys are ongoing at six sites in or around Morrinsville to get an idea of how bat activity changes across seasons and in response to weather.
Eventually, with the help of a bat expert, Mason hopes to find out how big their population size is, the trend in population and their habitual movements.
In the meantime, he urged members of the community to get involved by leaving big trees in place and contributing to the survival of bats through pest control.
‘‘What people do on their private land is very important for the survival of the longtailed bat nationally.’’
Trees such as pu¯ riri, to¯ tara, pukatea, old exotic trees like macrocarpa, pine and gum and old willows beside ponds – where the bats can feed on aquatic insects – also act as roosts.