The Lizard Fauna of Humid Forests on the Proposed Wadjana Basin Preserve
Total Page：16
File Type：pdf, Size：1020Kb
THE LIZARD FAUNA OF HUMID FORESTS ON THE PROPOSED WADJANA BASIN PRESERVE Cygnet Surveys & Consultancy 2011 Specialist Consultancy THE LIZARD FAUNA OF HUMID FORESTS ON THE PROPOSED WADJANA BASIN PRESERVE Cygnet Surveys & Consultancy 2011 Prepared by: Cygnet Surveys & Consultancy 2 Acron Road, St Ives 2075 NSW AUSTRALIA Email: [email protected] For: Vale Nouvelle-Calédonie Date: 1st May 2011 Bibliographic Reference: Sadlier, R.A. & Swan G. & Astrongatt, S., 2011. The Lizard Fauna of Humid Forests on the Proposed Wadjana Basin Preserve. Unpublished report by Cygnet Surveys & Consultancy to Vale Nouvelle-Calédonie. 19pp. Frontcover: Rhacodactylus sarasinorum – photo Ross A. Sadlier CONTENTS 1 INTRODUCTION .......................................................................................1 2 STUDY SITES AND METHODS.............................................................. 2 2.1 Study sites......................................................................................... 2 2.2 Field methods................................................................................... 6 3 RESULTS .................................................................................................... 8 3.1 Distribution and abundance....................….....…………….…...... 8 3.2 Assessment of survey methods ..................…….....……………... 11 4 ASSESSMENT............................................................................................ 13 4.1 Species diversity ........................................………….…………..... 13 4.2 Significant species ......................................………….………….... 14 4.3 Restricted species ........................................………….…………... 15 4.4 Conservation significance the Wadjana humid forests ............... 15 4.5 Threats to the Wadjana humid forests ...................................….. 16 5 RECOMMENDATIONS ........................................................................... 17 6 SUMMARY ................................................................................................. 18 7 ACKNOWLEDGEMENTS ....................................................................... 18 8 KEY REFERENCES .................................................................................. 18 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy ii Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy 1. INTRODUCTION This study was undertaken to determine the species diversity of lizards in humid forest habitat of the proposed Wadjana Preserve. Previous studies in the region of the Goro Plateau (Sadlier & Shea 2004; Sadlier 2006; Sadlier & Swan, 2009b) have identified humid forest as the habitat with the greatest diversity of lizard species. In the region a group of 19 species of lizard have now been recorded from the humid forest that covers the Special Reserves Forêt Nord, Pic du Grand Kaori and Pic du Pin and proposed Kwè Nord Range Preserve. A lower, but still significantly diverse lizard fauna is also found in the tall canopied maquis habitat (paraforestier and preforestier) of the region (Sadlier & Swan, 2009a; Sadlier & Swan, 2010; Sadlier & Swan, 2011). Preservation of humid forest habitat in the Grand Sud has been identified as a major priority for conservation of the rich endemic for lizard fauna of the region (Sadlier 2006). The forests of the Goro Plateau and adjacent ranges are highly fragmented and are present as a number of isolated patches of varying size across the landscape - this makes them particularly susceptible to a range of threats, particularly with increased levels of activity in the region since the commencement of mining activities. Not only do these forests have a high species richness, they are also the preferred habitat for the giant geckos Rhacodactylus leachianus and Rhacodactylus sarasinorum, the later a regional endemic and found only in humid forest habitat. Vale Nouvelle-Caledonie has proposed the preservation and management of humid forest in the Wadjana River drainage and Kwe Nord range to complement the network of existing humid forest habitat reserves represented by the Provincial Reserves in the Grand Sud. As part of the management of this area base-line inventories for lizard fauna in humid forests of the Wadjana River were undertaken to determine species richness and relative abundance, and to detect the presence of regionally significant species. 1 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy 2. STUDY SITES AND METHODS The study was conducted in the wet season in of January 2011. The conditions during the survey varied with periods of intermittent wet weather throughout, particularly in the early and latter part of the survey period. Two separate sites were investigated, each representing a discrete patch of humid forest in the area proposed for preservation. 2.1 Study sites. Two sites, each representing an area of tall humid forest were sampled, one in the upper and one in the lower reaches of the Wadjana River. Each site had three transect lines, each transect line containing 20 transect stations (5-8 metres apart) respectively. The vegetation structure at each site was internally relatively homogenous. Both sites had a tall (site B) to very tall (site A) canopy with a relatively open understory of saplings, palms, and pandanus: • Site A (0706231E 7533480N): three transects commencing near the edge of the forest closest to the creek line and passing through tall humid forest on a broad area with a gentle slope at the base of the range, then ascending a steep incline with areas of outcropping peridotite. The forest at the base of the slope had a moderately dense leaf litter layer, fallen logs and a sparse scattering of exposed rock on the surface, but changed markedly to being predominately outcropping rock with few fallen logs and scattered leaf litter piles on the steep slope. The majority of stations (~80%) were placed in forest at the base of range and the remainder on the steep slope with outcropping peridotite. • Site B (0704987E 7535501N): three transects each commencing near the edge of the forest close to the creek line and passing for a short distance (~20m) through moderately tall humid forest at the base of the range, then ascending a steep incline with areas of outcropping peridotite. The tall forest at the base of the slope had a moderately dense leaf litter layer with some fallen logs and a sparse scattering of exposed rock on the surface; it then changed markedly to being predominately outcropping rock with few fallen 2 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy logs and scattered leaf litter piles on the steep slope. The majority of stations (~70%) were placed in on the steep slope with outcropping peridotite. Location of Wadjana Basin study sites examined in January 2011.. Survey sites (alphabetic) and limits of replicates (numeral) are in white. 3 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy Forest patch on lower reaches of the Wadjana River - site A. Site A forest interior – base of slope. 4 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy Forest patch on upper reaches of the Wadjana River - site B. Site B forest interior – note steep slope and extensive outcropping peridotite. 5 Lizard Fauna of the Wadjana Humid Forests Cygnet Surveys & Consultancy 2.2 Field methods. Scincid lizards are the most diverse group in New Caledonia in terms of number of species and the niches occupied, and include: - secretive species that shelter and forage below the surface of ground cover. - diurnal surface-active species that tend to forage and bask on the surface of ground cover. - diurnal surface-active species that are arboreal in habits and tend to forage and bask on the trunks and foliage of trees, and are occasionally active on the ground. Previous studies to assess the diversity and abundance of lizard species in forest and maquis habitats have shown that strategically placed glue traps are the most time effective method for detecting the presence of the majority of day active skinks, and are also particularly effective in detecting the presence of secretive species when placed at the entrance to likely sheltering sites. For these reasons this was the method used to detect diurnal and secretive lizard species in all habitats across the 7 sites surveyed. Glue traps were strategically placed at each of 20 stations (5-8 metres apart) located along each transect line for each replicate. Traps were placed under or next to sheltering sites (crevices and cracks created where outcropping cuirasse boulders contact the ground, under and next to logs), in areas of litter or amongst surface debris, and under vegetation. For each trap placed at each station along a transect line the basic microhabitat attributes of the station with regard to potential sheltering sites were recorded. Geckos are usually the less diverse of the two lizard groups present. Geckos are active at night and forage in low shrubs, small trees, or the forest canopy, and shelter by day in vegetation or under cover on the ground. Nocturnal searches were usually undertaken in the first two hours after sunset. The method used to search for geckos detecting the reflection from the eye when a beam of light is directed towards the lizard or, by scanning vegetation with a powerful light at closer range to observe geckos on twigs or branches. Binoculars modified to carry a torch and emit a light beam from below the eyepieces of the binocular