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Published: 2012-07-02 00:00:00

The first city-wide survey of long-tailed bats in Hamilton is a major step towards the city remaining home to this threatened species.

The Hamilton City Bat Survey 2011-2012, released in May this year, provides better understanding of distribution and behaviour of long-tailed bats in Hamilton, which is important for their conservation.

Bat detectors, which pick up high frequency sounds of bats inaudible to humans, were placed at 62 sites where bats might be in Hamilton.

Bats were detected at 16 sites, all in the most southern urban-rural fringe of the city and mainly in major gullies or waterway margins within 100 metres of the Waikato River. However, the most bat activity was detected at Whewell’s Bush, an 11 hectare native forest remnant at Tamahere.

The survey was conducted by Project Echo partners and environmental consulting group Kessels & Associates Ltd.

Kessels & Associates managing director Gerry Kessels said: “If Hamilton is to keep its long-tailed bats, we need to better understand them, but also make our urban areas conducive to them surviving and remaining.

“The survey shows bats’ preferred habitats are the less well lit and better vegetated gullies around the southern fringes of the city and along the Waikato River,” Mr Kessels said.

Consistent with international studies on urban bats, Hamilton’s population shows sensitivity to roads, buildings and artificial lighting which possibly cause barriers for the bats to connect with their natural habitats. Mr Kessels thinks this may explain why bats were not located during the study at Claudelands Bush (Jubilee Park/Te Papanui), the Kirikiriroa and Waitawhiriwhiri gullies or urban areas north of Cobham bridge.

Feeding solely on flying insects, bats will opportunistically feed around lights, such as those at the Waikato Stadium, from time to time.  But they still need well-vegetated and less well lit gully and river edges and forests for their main habitat requirements, Mr Kessels said.

“Because of development pressure on gullies and other bat habitats within and around the city, we thought it would be useful for the councils, developers and for people restoring gullies to know where the important bat habitats are, so they can plan and design in advance and more sensitively.

“We need to remember that just because bats are here, it doesn’t mean they are common or that their population is stable. We still don’t know what these populations are doing – if they are in decline or increasing, and we don’t know how animal pests, such as cats and rats and possums are affecting them,” Mr Kessels said.

Hamilton is thought to be one of only two New Zealand cities with a resident population of long-tailed bats. The species is one of the two remaining native land mammals in New Zealand (the other being the lesser short-tailed bat) and is classified as ‘nationally vulnerable’ in the North Island.

The survey received funding and in-kind support from Waikato Regional Council, Hamilton City Council, the Department of Conservation, Kessels & Associates, Darren and Noa Le Roux, Associate Professor Stuart Parsons from the University of Auckland, Professor Bruce Clarkson from the University of Waikato, the Waikato Tree Trust and the Riverlea Environment Society.

For more information on Project Echo visit www.waikatoregion.govt.nz/projectecho