Precious froglets arrive in time for Leap Year

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MEDIA RELEASE

28 February 2008

Precious froglets arrive in time for Leap Year

What looks at first to be a slimy mess in a Petri dish represents a highly-significant advance in conservation and restoration ecology.

Ecologists from both the Sanctuary and Victoria are celebrating the arrival of the first Maud Island frogs (Leiopelma pakeka) to hatch on mainland New Zealand for many years.

Clustered together to conserve moisture, the 13 fingernail-sized froglets in the photograph were recently transferred from the Karori Sanctuary to Victoria University where they will be incubated and later released as young frogs.

No larger than a human adult’s little fingernail, the Maud Island froglets differ from most frog species in that they hatch from the egg as fully-formed froglets without going through the usual tadpole stage.

13 froglets in total were found during a recent audit of a specially-constructed frog research enclosure at Karori Sanctuary.

“Sixty frogs were released into the special mouse-proof enclosure in 2006 in an effort to re-establish this highly-endangered species on the mainland,” Victoria Master's student Kerri Lukis says. Ms Lukis is studying the Sanctuary population for her Master's thesis under the supervision of Associate Professor Ben Bell, Director of the University's Centre for Biodiversity and Ecological Restoration.

She says that thirty of frogs released in 2006 were later released outside of the enclosure so that the captive and wild populations could be compared. When it came time to find the frogs again to see how many frogs had survived and whether they had bred she was delighted to find the 13 froglets attached to adult males.

"This is extra special because Maud Island frogs have never been found breeding in their natural habitat before, and certainly not on the mainland.

"It's wonderful timing for 2008 - international Year of the Frog – and a Leap Year. It’s rare to get a ‘good news’ story about frogs – every year around 35 species of frog become extinct and two of New Zealand’s remaining native frog species are on the critical list."

While not the rarest species, the thimble-sized Maud Island frogs are nationally threatened. Like all of New Zealand’s native frog species, they are endemic (found only here) and belong to the endemic genus Leiopelma.

They have evolved very little over the last 70 million years, resulting in some very distinctive features and behaviours. For example, they don’t croak, live in water, have webbed feet, or go through a tadpole stage.

Associate Professor Ben Bell says the University and the Sanctuary have worked closely together on this project.

“It is good to know that the Karori Sanctuary frogs are able to breed in an enclosure there. Whether those frogs released into the wild in Karori survived and bred is less certain at present.”

ENDS

FROG FACTS

Frogs are regarded by scientists as environmental bio-monitors. They are particularly sensitive to changes in their environment and, as such, can be an early warning of environmental threats. However, this often means they are one of the first groups to die out when their environment changes.

Major causes of extinction/declining populations are: Loss/fragmentation of habitat; environmental pollutants; diseases (especially chytird fungus), and introduced predators

Because New Zealand’s frogs evolved in isolation, and in an environment free of predatory mammals, they have been especially susceptible to introduced predators, the colonisation of non-native frogs, and the diseases they brought with them. Of the seven known species of endemic NZ frog, only four have survived into the 21st Century.

Maud Island frogs (Leiopelma pakeka) are one of only four surviving native frog species. All are nationally threatened, with the rarest, Hamilton’s frog (Leiopelma hamiltoni), numbering less than 300. All of New Zealand’s native frog species are endemic and belong to the genus Leiopelma. They have evolved very little over the last 70 million years, resulting in some very distinctive features and behaviours:

They don’t croak but can make ‘chirping’ sounds
They have round eye pupils (not slits)
They have no external eardrums but can sense vibrations
They don’t have webbed feet
They are nocturnal
They live on land in shady, moist forested areas or ridge tops
They don’t have a free tadpole stage – eggs are laid under rocks or logs and in most species the male sits over the eggs until they hatch as well formed, tailed froglets
They eat a variety of insects and spiders and catch their prey by grabbing it with their mouth (they don’t flick their tongues out)
They can live for more than 30 years.

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