NZ's urban lizards need help

Tuesday, 24 December 2019

Northern grass skink (Oligosoma polychroma) basking on concrete pavers. Northern grass skinks are the most abundant skink in Wellington and Nelson and are often seen basking on sunny days. Catalyst story on urban lizards.

Your back garden might be a great place to conserve New Zealand's declining lizard population.

Many native skinks and geckos have ranges of less than 20 square metres – space found in many back gardens – and new research is asking whether urban 'wildlife gardening' might be a necessary way to conserve the species.

Skinks and geckos are fully protected by law and should not be handled or disturbed, Victoria PhD student Chris Woolley says.

But they can be encouraged in back gardens by removing predators and creating lizard-friendly habitats.

* Riccarton Bush a precious remnant of Canterbury's ecological past

* New Zealand: Land of the lizards

* Lizards: Attract skinks and geckos to your garden**

'Cities may offer unique opportunities for lizard conservation,' Woolley and colleagues wrote in a science paper published this month.

Kiwis can help conserve skinks and geckos in their gardens by providing native plants, rocks and cover from predators with small sheets of roofing iron, for example. Untidiness is good.

Large scale conservation of urban lizards is blue sky thinking at this point, Woolley says.

He talks about 'potential for restoration'.

Other biologists have for years researched lizards in rural and wild areas.

Woolley's contribution is to acknowledge that lizards live in cities and start asking if city folk can help stop lizard decline and maybe even reverse it.

'A lot of things have to take place in cities to achieve those lofty goals,' he says.

With colleagues, he found that 37 per cent of geckos and 39 per cent of skinks had ranges that historically included the country's largest six cities.

The copper skink is thought to be the only species of native lizard found in Hamilton. They are also found across the North Island including in Auckland and Wellington.

These animals didn't probably didn't populate cities. Rather cities grew up in their habitats.

Based on records going back 20 years, Auckland today has three gecko and four skink species. Hamilton has zero geckos and two skinks. Wellington has three geckos and five skinks.

Nelson has zero geckos and two skinks. Christchurch has one gecko and three skinks. Dunedin has zero geckos and two skinks.

These records exclude the invasive rainbow skink from Australia, which is established in Auckland and Hamilton. As well, there may be lizard populations just outside urban areas.

Nonetheless, 'the diversity of lizards in all of the cities has declined dramatically since human colonisation', the authors wrote.

Officials have in recent years translocated lizards to fenced enclosures such as Zealandia in Wellington and Riccarton Bush in Christchurch, but these sites are small scale and expensive.

Raukawa gecko on a tree in Wellington at night.

Greater opportunities may exist in city public reserves and alongside sport and playing fields, but there needs to be 'indigenous-dominated' plantings and greater predator control.

Back yards, however, may offer good opportunities, Woolley says.

'There are things you can do to make your garden more wildlife friendly,' he says.

'For lizards, we talk about planting dense vegetation, things like grasses, sedges, flaxes and things that provide cover.'

Untidy gardens are especially good skink habitats, the authors wrote.

'We know that predators are a huge issue and things like crevices, where skinks and geckos can hide, are really important.'

Because skinks and geckos are small, their main predators are cats, hedgehogs and mice, he says.

Humans can also provide 'basking services'. Some lizards like to sun themselves on stones and rocks, but also need nearby crevices and hidey holes if a predator approaches. Others are nocturnal.

Many city Kiwis won't know they have lizards in their gardens. Indeed cat owners may only learn about their presence when tabby presents wounded or dead lizards.

DOC published a guide to lizard gardening in 2018.

The public should 'certainly not' attempt to move lizards themselves, Woolley said.

But helping out can be 'quite cool' and increasingly back garden biodiversity was a 'powerful thing', he said.