Threats to native reptiles and amphibians

All of our reptiles and amphibians are fully protected by law. It is illegal to collect skinks and geckos, and you need a special permit to keep them in captivity. This includes any skinks and geckos that you may find in your garden!

Despite this legal protection, a number of our native species are now extinct, and many others are endangered.

Historic and current threats include:

• predation or smuggling by humans

• predation by introduced species

• habitat loss

• disease

• pollution

• climate change

• increased UVB radiation.

The 3 most significant threats to our remaining populations of reptiles and amphibians are introduced species, habitat loss and disease.

Introduced mammalian species

Aotearoa New Zealand’s native species evolved in isolation for millions of years after the last land bridge to Gondwana was lost. Birds and insects dominated our ecosystems, and the only native mammals are 2 species of bat. Our native animals and plants evolved without developing defence mechanisms against many large predators. As a result of this unique history, animals introduced by Polynesian and European settlers have had devastating effects. We often hear about how vulnerable our birds are to these introduced species, but our native reptiles and amphibians have also been dramatically affected. For example, our native frogs had evolved a ‘freezing’ defence mechanism that is very effective against birds that hunt using sight but useless against mammals that hunt using smell.

Dogs and kiore were the first mammals introduced by Polynesian settlers over 1,000 years ago. This first wave of mammalian predators was responsible for the extinction of all tuatara from the mainland, as well as a number of lizard species, and 3 species of native frogs also became extinct before the arrival of European settlers.

Captain James Cook introduced the second wave of mammalian predators when he released rats, pigs and goats in 1769. As more European settlers arrived, they brought with them a number of other species, including cats and mice. Further introductions – some intentional and some accidental – included ferrets, stoats, hedgehogs and possums.

These introduced species are considered to be the greatest threat to our remaining populations of reptiles and amphibians. As a result, a lot of the conservation work focuses on offshore and mainland islands where these mammals can be eradicated.

Habitat loss and fragmentation

Since human settlement, loss of habitat has been extensive in New Zealand. Large areas of forest have been burnt or cleared for farmland. Wetlands have been drained or modified. Many streams and lakes have been dammed or altered for irrigation and electricity generation. Many habitats have also been degraded by agricultural run-offleaching and other pollution from our towns and cities. The largest areas of undisturbed terrestrial habitat are at higher altitudes and on offshore and mainland islands.

Habitat loss

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Deforestation results in the loss of habitat for many species. A large proportion of New Zealand’s native forest has been cleared for farming and settlement.

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Although the rate of habitat loss is slower than in the past, it is still considered a significant threat to our remaining populations of reptiles and amphibians – while predation may only affect certain species in an area, habitat loss affects every species.

A major concern is that much of the remaining or restored habitat is fragmented, meaning that these habitats are isolated from each other and the populations living there are even more vulnerable to extinction. Fragmented habitats can only support smaller populations that are more vulnerable to disease and predation, it’s unlikely that new animals will naturally move into the area, and it’s more difficult for individuals to meet their needs for food and shelter.

Disease

Our native reptiles and amphibians are also threatened by disease.

Frog swabbing

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Dr Phil Bishop and his colleagues swab frogs in the wild to test for the chytrid fungus.

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Our native frogs are particularly at risk. Their delicate, semi-permeable skin allows them to absorb moisture and air from the surrounding environment, but this increases their exposure to toxins, bacteria, fungal infections and viruses.

Chytridiomycosis is a particularly worrying disease affecting frogs in New Zealand and around the world. It is caused by the chytrid fungus, which originated in Africa and was spread when people shipped a species of frog used for pregnancy testing around the world. Scientists are not exactly sure about how the fungus works. They know that it attacks the skin, and this may affect the ability of frogs to stay hydrated. Some scientists believe that the fungus secretes a toxin that eventually poisons the frog. Chytridiomycosis was first discovered in New Zealand frogs in 1999. It has affected both populations of Archey’s frogs, and scientists are very concerned about the spread of this disease to our other native frog species.

Scientists are also concerned about the risk of diseases carried by mosquitoes and other insects that have the potential to affect our native reptiles and amphibians. For example, in other parts of the world, lizard populations have been affected by lizard malaria. Phil Bishop is passionate about frogs and talks about his research into frog disease.