Conservation monitoring for Duvaucel's geckos

Over millions of years, a myriad of lizards evolved to live on this beautiful whenua we call Aotearoa New Zealand, adapting to inhabit its various ecological niches. So far, 48 species of gecko have been discovered and described here - yet most of these incredible species creep under the consciousness of many Kiwis.  

The largest of these is the Duvaucel’s gecko – which is also one of the biggest geckos in the world - and was named after the naturalist Alfred Duvaucel (1793-1825). A robust and long-lived animal, they can grow up to 30cm long and can live for more than 60 years.

Just this year, DNA sampling has revealed that what was previously thought of as one gecko has now been recategorised as two genetically distinct species – the Duvaucel’s gecko (Hoplodactylus duvaucelii) and te mokomoko a Tohu / the Tohu gecko (Hoplodactylus tohu).  

The former was once widespread throughout New Zealand’s North Island, but introduced predators and habitat destruction have meant that naturally occurring populations are restricted to 36 offshore islands. The species has a conservation threat status of ‘at risk’ and it is estimated there are approximately 20,000 mature individuals. The Tohu gecko is in much more dire straits - with an estimated 600 individuals surviving in the wild today, and is found on Cook Strait's Ngāwhatu-kai-ponu/Brothers and Kuru Pongi/Trios Islands.

These nocturnal geckos are beautiful to behold, ranging from olive-brown to green tones reminiscent of bark or lichen, with individualised mottled patches of colour down their backs, and a pale grey underside. They inhabit lowland forests, flax lands and coastal areas and during the day like to hide out in tree hollows, under logs and stones, or within rock crevices and petrel burrows.

Auckland Zoo’s ectotherm keeper Chye-Mei has cared for Duvaucel’s geckos for many years throughout her zookeeping career, which has included assisting with disease screening for the species on Repanga/Cuvier and Kawhitu/Stanley Islands. 

Chye-Mei is the Zoo and Aquarium Association (ZAA) ‘studbook co-ordinator’ for Duvaucel’s geckos, within Australasia. As part of this role, she will help to provide breeding recommendations and find placements for geckos within the programme. Since the taxonomic split between the two species occurred, she has been going through the provenance and parentage information provided by each zoo or wildlife organisation to confirm accurate numbers of each species.

In March of this year, Chye-Mei travelled to a predator-free island in the Hauraki Gulf to assist wildlife biologist Manuela Barry with monitoring geckos that were previously released there. A 10-year breed for release programme at Massey University (MU), managed by Manuela, saw multiple Duvaucel’s geckos released on two Hauraki Gulf islands in 2020, with the support of the Auckland Zoo Conservation Fund. The Zoo's curator of ectotherms Don McFarlane assisted with the release, and it was also attended by our head of animal care and conservation Richard Gibson.

Due to Covid-19 restrictions, and unprecedented weather events, this was the first survey to take place since this initial release. The team’s primary objective was to detect the ‘founder’ geckos (the first animals that were released) and assess their health and general condition.

Manuela has been working with Duvaucel’s geckos since 2006, and through the breed for release programme, successfully released geckos at five separate island locations. Though she transitioned away from academia in 2021, she continues to monitor the released populations at several sites, describing it as her ‘passion project’.

After a species is released into a new location, it’s important to understand whether the animals have been able to establish themselves there – and this is where post-release monitoring comes in. These surveys are generally undertaken over multiple years to ensure the most reliable data, and due to the slow reproductive rate of New Zealand's native geckos, confirming a species’ overall success or failure can take a decade or longer.

Each release site presents unique challenges - such as varying geology and the local flora and fauna that exist on the island. Releasing Duvaucel's geckos to different sites means that observations can be taken in different ecological contexts; this helps herpetologists to understand each location uniquely, and the species’ capacity to tolerate disturbances or unfavourable conditions. The data that is collected is invaluable for informing future conservation efforts.

Caring for lizards that are sometimes as small as 3cm, Chye-Mei says it’s incredible to work with a native species of this size and robustness. When asked what she loves about them, she explains, “they’re really versatile – they spend a lot of time on the ground in the absence of mammalian predators, and they also spent a lot of time in the trees. Their role in the environment is really interesting; they eat insects but they’re also really keen on fruit and nectar. This is often overlooked with geckos – their role as pollinators and seed dispersers within the ecosystem.”

During this survey, the team located 12% of the founder geckos. All of the geckos that were sighted were in great body condition, without any indication of sickness or having been predated on. In even more positive news, they discovered three island-born young geckos of different sizes and confirmed that one of the females was gravid (pregnant).

“Contributing to the conservation of Duvaucel’s geckos holds deep personal significance for me. Witnessing the collective efforts of government organisations, NGOs, conservation volunteers, researchers, and indigenous communities, to protect and restore our natural world is truly encouraging,” explains Manuela.

“Being part of this work signifies a positive step forward in rectifying past mistakes and ensuring the thriving of our native species. It is a privilege to contribute to the conservation of this taonga species and to play a role in preserving the rich biodiversity of New Zealand for future generations.”