Growing up to 20cm from nose-to-tail-tip, Otago green skinks are counted among the largest lizards in Aotearoa, though their impressive size has become their Achilles’ heel. The larger they grow, the more difficult it is to hide from the reach of a cat’s paw, or the gnawing bite of a rat.
Scenes of young and old Otago green skinks basking together under the sun have only recently become possible in coastal Otago, as Otago green skink populations have been disappearing from their former range on both sides of the Otago Harbour all the way to Outram since the mid-2000s.
Witnesses to their decline across the Otago region took action. Many were involved in the planning, including Prof Phil Seddon and master of wildlife management student Luke Johnston. Eventually, a team was assembled to trap skinks in one of their remaining habitats. In 2016 the combined efforts of Orokonui staff, volunteers and governance, led by herpetologist and PhD researcher Carey Knox, returned Otago green skinks to Ōtepoti Dunedin with the release of 40 wild skinks into Orokonui Ecosanctuary.
More than eight years later, I found myself, an American ecologist, delving into the story of those 40 skinks and how they have managed since their release. Animal relocations for conservation have been critical to preventing the extinction of many of Aotearoa’s native species, but it can take many years to determine whether a new population has done well enough to persist long term.
As I walk along a track in the sanctuary, trying hard to listen for quiet rustling in the grass (over the crunch of gravel under my boots), I walk up to an old rotten stump. At first glance, this decaying stump seems completely ordinary, easy to overlook, until the sun shines down at just the right angle, bringing with it the first warmth of a new day. Drawn out from their subterranean shelters, six sleek, moss-coloured lizards cautiously peek their heads out of the darkness, glance at one another, and begin their day of dancing around the shadows cast by the regenerating forest.
As a part of my MSc in ecology with the University of Otago, I wanted to find out if the new Otago green skink population had grown beyond the 40 individuals released in 2016. To do this, I needed to identify as many individual skinks as possible.
How do I tell them apart? Like stripes on a zebra, the patterns on skink scales are unique to each individual and stay the same for their whole lives, so I could make a photo-library of all the ID photographs of skinks I had caught to compare their markings.
I also needed to find out if skinks were able to complete their full lifecycle in this new habitat. Otago green skinks, like most lizards in Aotearoa, take several years to mature (about three years for Otago green skinks) and can live a long time. The lifespan for Otago green skinks was conservatively estimated to be at least eight years, so I wasn’t sure if any of the founding members, which would have been at least three years old when they were released, would still be there.
After many days of catching, and cataloguing, and comparing photographs of skinks, I identified 57 individual Otago green skinks living in Orokonui Ecosanctuary. Imagine my delight when I compared baby photos of a skink born in 2016 to photos I took this year and realised that it was the same skink, all grown up. Three of the skinks I found were members of the original 40, which would make them at least 11 years old now, bumping up the minimum age by three years. The Otago green skink population in Orokonui Ecosanctuary is growing, and skinks there can live full lives when protected from most introduced predators.
Conservation success stories like this are encouraging when 94% of Aotearoa’s 124 native reptile species are threatened with extinction or at risk of becoming threatened soon. The biggest threats to native reptiles are predation by introduced mammals (cats, rats, stoats and weasels, hedgehogs, and mice), and widespread habitat modification. Orokonui Ecosanctuary has been a safe-haven for so much of Aotearoa’s unique and endangered wildlife, and is now, happily, a home for generations of Otago green skinks.
You can help support a future for green skinks and other amazing reptiles by visiting and supporting sanctuaries such as Orokonui, or taking action in your backyard by trapping pests and building a lizard garden. To learn more about what you can do to help local wildlife, visit https://orokonui.nz/.
Pearl Barry is a MSc student researching Otago green skinks under the supervision of Dr Jo Monks and Carey Knox at the University of Otago. Each week in this column writers address issues of sustainability.
