A Victoria University postgraduate student studying Maud Island frogs in the Zealandia eco-sanctuary has made an interesting discovery.
In 2006, Zealandia staff translocated 60 frogs to the sanctuary, placing 31 into purpose-built enclosures and releasing 29 into the open. None of the 29 had been sighted for some years, and conservation staff thought it possible resident kiwi and mice may have got the better of them.
However Tanya Karst, a postgraduate student from Victoria’s Centre for Biodiversity and Restoration Ecology who recently started her field study on the threatened nocturnal Maud Island frog (Leiopelma pakeka), was excited to find this wasn’t the case.
“We were really pleased to find a subadult frog under rocks outside the main pen. It was almost three years old, so had survived for some time, despite the presence of potential predators,” she said.
Zealandia’s Conservation Manager Raewyn Empson was happy to hear of the find.
“Finding the frog outside the enclosure was great. It confirmed that at least a pair of frogs survived and bred there after release, and at least one juvenile has survived to three years of age – there were concerns that all had disappeared despite the fact that they are cryptic. There could be more.”
Karst’s study is on mortality mitigation of this rare New Zealand frog in Zealandia and aims to assess the likely threats on Maud Island frogs within the sanctuary, particularly the impact of little spotted kiwi and house mice.
“A fence around the frog habitat (15m x 12.5m) excludes kiwi from the site, and more rocks and logs have been added to improve the habitat. Movements and numbers of mice will be carefully monitored within the area the frogs occupy,” she said.
On Sunday, the Zealandia frog population was supplemented with 100 additional frogs from Maud Island to enhance their survival prospects.
Dr Ben Bell of Victoria University supervises Karst’s project.
“The frogs are known to have bred in Zealandia for six successive years, so clearly the conditions there are suitable for breeding them.
“Tanya Karst’s study will further document the growth and survival of these frogs, providing important information on the rearing success of young, as well as on the survival of adults,” he said.
Tanya Karst holding a frog on Maud Island/Te Hoiere (Photo: Siobain Browning)
What’s special about New Zealand’s frogs?
Nicola Toki explains it nicely:
“Our frogs don’t croak, don’t have an eardrum, have large round pupils in their eyes, and don’t have an aquatic tadpole stage to their life cycle!”
How can you tell how old a Maud Island frog is?
Nutritional intake has an effect on growth but in general, if the diet is healthy, during the growth phase you can determine age from snout-vent length. After it’s reached adult size, unless you’ve tracked its growth, you cannot tell its age.
Mice at Zealandia
Mice have been present at Zealandia in low numbers since shortly after the 2000 eradication. Numbers are kept down with yearly control work. For more information see: Pest eradication
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