New Zealand Hoplodactylus Alpine Gecko Modelling
One of our environmental projects involves habitat modelling for a group of recently discovered native Hoplodactylus alpine geckos in the South Island of New Zealand. The Hoplodactylus alpine geckos are relatives of the forest gecko, but occupy very different habitats, namely alpine rock bluffs, boulder piles and scree above 1,000 metres. They seem to be extremely rare.
We hope that our spatial modelling has helped identifying locations where these alpine geckos might be found in the South Island, by analysing sites of ideal habitat conditions where they could live.
For the pilot project the entire South Island was modelled using the weights of evidence technique to identify potential habitats for Hoplodactylus alpine geckos. This technique allows data to be assessed and weighted according to how great its influence is in relation to the current known locations of these geckos. A number of features important for alpine gecko’s habitat, such as elevation and soil type, were identified using documentation and expert knowledge from the Department of Conservation (DOC). Identifying the key elements that make up their habitat was essential before testing began in this project, and helped determine which maps to include in the model.
Data for the model was obtained from Land Environments New Zealand (LENZ), National Institute of Water and Atmospheric research (NIWA), Landcare Research and GNS Science. The data has been managed in a GIS and manipulated using techniques such as grid extrapolation, grid interpolation, theme classification, and neighbourhood statistics. All themes developed for the model were 100 m by 100 m resolution grids covering the entire South Island.
Example of reclassified themes used in the model.
The resulting predictive map highlighted the most favourable areas for Hoplodactylus alpine gecko habitat in the South Island. Areas that were identified correlated well with new alpine gecko locations found by DOC researchers. These were not included in the original model and have thereby verified it, giving us the confidence to continue with more detailed regional modelling of alpine gecko habitat in the South Island.