Improving the management of Canterbury’s lizards

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Ecology
Degree name
Master of Science
Publisher
University of Canterbury
Journal Title
Journal ISSN
Volume Title
Language
English
Date
2021
Authors
Turner, Matthew Kendall
Abstract

Monitoring tools are integral for the conservation and management of lizards in New Zealand, providing inventories of species or insight into the dynamics of lizard populations. Many of New Zealand’s lizards are cryptic, and on the mainland occur at low densities, making them difficult to detect and monitor. Therefore, tools used for monitoring lizards must be robust, efficient, and safe for the lizards.

Current artificial refuge designs used in New Zealand are vulnerable to trampling and disturbance from large mammals. Forty novel concrete artificial refuges resistant to trampling, were placed on the Port Hills, Christchurch in 2015. I measured the use of these refuges by lizards and how temperature and microhabitat influence lizard occupation. In monthly checks of the concrete refuges between February 2020 and January 2021, I recorded 420 Waitaha geckos (Woodworthia cf. brunnea) and 39 skinks (Oligosoma aff. polychroma Clade 5 or O. maccanni). Geckos had little seasonal variation in occupancy unlike skinks which were found at lower numbers and most frequently during winter. Gecko occupancy was highest at low ambient temperatures when the internal refuge temperature was below ambient, with geckos in the field being observed in refuges as cold as 2.4 ℃. The summer thermal profile of concrete refuges was within the published thermal preference of Waitaha geckos. Microhabitat variables recorded in this study had no observed influence the occupation of the concrete refuges on the Port Hills by lizards. Using a pre-existing dataset of the occupation of Onduline artificial refuges on Banks Peninsula revealed geckos were significantly more common in refuges close to areas of leaf litter and skinks in refuges with low exposure.

The monitoring of arboreal populations of geckos in New Zealand is difficult. Artificial refuges are one method used for their detection, with multiple different designs being tested in New Zealand. I investigated four different designs of artificial refuges for arboreal geckos to determine which was the most effective for detecting an arboreal population of Waitaha geckos in Riccarton Bush. One of each refuge was placed on 20 trees. Refuges were checked once a month from May 2020 to January 2021. A total of 11 detections of geckos were made, including six different individuals, four recaptures and one sloughed skin. The multi-stacked Onduline design was the most effective for detecting these lizards with 73% of observations.

Pitfall trapping is widely used in New Zealand to capture terrestrial lizards, but the design of pitfall traps often varies across trapping operations. Lizards can be trapped for up to 24 hours and may be exposed to heat stress during warmer weather, a risk which will increase with future global warming. I tested the effects of cover material, cover colour and trap size on trap internal temperatures on Kaitorete Spit for 24 days during winter 2020 and summer 2020-21. Wide day-to-day variation was observed during the summer, with the maximum internal temperature reaching 38.1 ℃. Cover material, cover colour and trap size all had a significant effect on internal temperatures, with brown plywood covers with a 4 litre trap size having the lowest summer maximum internal temperatures.

This research may benefit future conservation efforts on lizards through safer, more efficient monitoring tools. The provision of refuges resistant to trampling may enable monitoring in environments deemed to be at high trampling risk.

Description
Citation
Keywords
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Rights
All Rights Reserved