Auckland Council gecko monitoring programme

This work consists of developing a long-term gecko standardised monitoring programme for the Auckland Council to be undertaken at four biodiversity sanctuaries in Regional Parks. Information gained from the programme will advance understanding of the effects of conservation management on cryptic herpetofauna populations within the Auckland Region. The objectives of the monitoring programme are to:

• Quantify gecko population dynamics at Tawharanui, Shakespear, Whakanewha and Waitakere Ranges (Ark in the Park) Regional Parks
• Track changes in the population dynamics of geckos over time, as determined by spatial distribution, relative abundance and population structure
• To the extent possible, assess the effects of pest management (control vs. eradication) on geckos through the use of appropriate reference sites (Whakanewha) and baseline data (Shakespear)
• Allow for the potential to address research questions that lead to improvements in monitoring techniques and a greater understanding of gecko population drivers.

Herpetofauna (reptiles and amphibians) are important biological indicators of ecosystem health and are integral components of ecological communities worldwide and in New Zealand. However standardised survey and monitoring methodologies for some New Zealand herpetofauna are lacking, particularly for cryptic and arboreal lizards such as forest geckos (Mokopirirakau granulatus), Pacific geckos (Dactylocnemis pacificus) and Auckland green geckos (Naultinus elegans). Some of these species may still be relatively abundant in the Auckland area, especially within some of the Council Parks undergoing predator control. Geckos are therefore one of the potentially more useful fauna for long-term monitoring programmes measuring responses to management, given their susceptibility to mammalian predators, combined with relatively long population trajectories and slow life histories (long lived, late to maturity, and few offspring/female/year).

The selected methods include closed-cell foam covers, and visual encounter surveys.

VES (visual encounter surveys) and habitat searching have been standard survey techniques for monitoring herpetofauna worldwide and are typically the only methods employed for detecting arboreal lizards in New Zealand. However these methods rely heavily on the consistency of a number of variables (e.g. observer experience, weather conditions, temperature, survey timing) to provide comparable results. A lack of basic ecological knowledge of the species being surveyed or monitored further confounds these issues, particularly when dealing with rare and/or cryptic fauna.

A recent advance, which potentially overcomes some of these issues, was the development of a new monitoring tool for cryptic nocturnal gecko species. This was the use of gecko covers, using closed cell-foam (CFRs, Bell 2009). This has presented an opportunity to reduce the current reliance on VES for some species and potentially gain comparable information on population density and dynamics, especially over time. Cell foam retreats (CFRs) are installed on tree trunks and provide nocturnal, arboreal geckos with diurnal shelters that can be easily inspected for occupancy (Bell 2009). It is unclear whether diurnal Naultinus geckos are likely to use diurnal retreats and VES continue to be a more appropriate survey method for these species.

Tawharanui Open Sanctuary, Tawharanui Regional Park. A 588 ha ´open´ sanctuary with a 2.5 km Xcluder Pest Proof fence (built in 2004), which integrates conservation with farming and recreational use. Pests controlled include mice, ship rats, Norway rats, weasels, stoats, ferrets, cats, possums, rabbits, hedgehogs, using an aerial drop of poison, along with ongoing ground-based control efforts. Only mice, rabbits and hedgehogs persist. Lizard species include forest geckos (Mokopirirakau granulatus), Auckland green geckos (Naultinus elegans) and shore skink (Oligosoma smithi).

Shakespear Regional Park, Whangaparaoa Peninsula. A 555 ha ´open´ sanctuary with a 1.5km Xcluder Pest Proof fence across the peninsula. Pests controlled include mice, ship rats, Norway rats, weasels, stoats, ferrets, cats, possums, rabbits, hedgehogs, using an aerial drop of poison, along with ongoing ground-based control efforts. Only mice, rabbits and hedgehogs persist. Lizard species confirmed include Pacific gecko (Dactylocnemis pacificus), Auckland green geckos (Naultinus elegans) moko skink (Oligosoma moco), ornate skink (O. ornatum), copper skink (O. aeneum) and the introduced rainbow skink (Lampropholis delicata).

Ark In The Park, Waitakere Ranges. A 2000 ha pest-controlled park administered by the Auckland Council and Forest & Bird Waitakere Branch. Lizard species confirmed in Ark include forest gecko (Mokopirirakau granulatus) and the introduced rainbow skink (Lampropholis delicata).

Whakanewha Regional Park, Waiheke Island. A 247 ha pest-controlled park naturally free of possums, ferrets and weasels and has had intensive pest control since 1994. Lizards detected in Whakanewha include forest geckos (Mokopirirakau granulatus) and Auckland green geckos (Naultinus elegans) although Pacific geckos (Dactylocnemis pacificus) or ornate skinks (Oligosoma ornatum) have not been confirmed yet.

This work is in collaboration with Bioresearches Group Limited.