Biodiversity Monitoring in Rewanui Initial Lizard Survey for November 2008
Total Page：16
File Type：pdf, Size：1020Kb
Biodiversity monitoring in Rewanui Initial lizard survey for November 2008 Nyree Fea FOR FURTHER INFORMATION Greater Wellington Publication date July 2009 Regional Council Publication No. GW/BIO-G-09/189 Masterton PO Box 41 File No. WB/05/05/02 ALL PHOTOS IN THIS REPORT T 06 378 2484 ARE SUPPLIED BY MARIEKE F 06 378 7994 LETTINK. W www.gw.govt.nz Contents 1. Summary 5 2. Introduction 5 3. Methods 6 4. Results 7 5. Discussion 9 6. Acknowledgements 11 7. References 11 Appendix A 12 1. Summary Lizard surveys were conducted in Rewanui Reserve, in the eastern Wairarapa, in November 2008 by the Greater Wellington Regional Council (GW). This initial general survey covered a variety of lizard habitat types from rock outcrops, talus slopes and native and exotic bush. Techniques used to search included visual and hand searching, pitfall trapping and the use of artificial cover objects. The survey found 53 individual lizards with 45 common geckos, six common skinks, and two unidentified lizards. This diverse property has surviving lizard populations benefitting from the extensive pest control carried out by Greater Wellington and the property managers, the Montfort Trimble Foundation. Further surveys are needed to determine if threatened lizard species are also present. 2. Introduction GW is contracted by the Montfort Trimble Foundation to monitor biodiversity within the diversely managed Rewanui property. This project is funded for three years by a Sustainable Farming Fund administered by the Ministry of Agriculture and Forestry. Control of pest animals and plants in this reserve is conducted by GW under its Key Native Ecosystem (KNE) programme, and by Trevor Thomson of the QEII Trust under contract to the Trimble Foundation. Monitoring of indicator species is scheduled to be phased in gradually in the project’s first year from July 2008 to June 2009. Monitoring biodiversity (biological diversity; ie the variety of fauna and flora present in an ecosystem) allows one to assess the relative health of an area and its resilience to environmental and human-induced change. A diverse ecosystem has more connections between species and this complexity bolsters it against disturbance as each species is less reliant on the next. Monitoring of native lizards is useful in assessing overall ecological status of New Zealand reptiles and the impact on populations from habitat modification. Lizards are an important component of ecosystems, acting as seed dispersers and pollinators as well as predators of invertebrates. They are hunted by some birds and pest mammals such as moreporks, magpies, kingfishers, rodents, mustelids, hedgehogs and cats. Determining the presence or absence of lizard species previously recorded in the region and especially the occurrence of threatened species is a useful indicator of ecosystem health. Table 1 lists lizard species previously recorded in the eastern Wairarapa region (from the Department of Conservation (DoC) Herpetofauna Database) and their current threat status according to the most recent edition of the national threat classification by Hitchmough et al (2007). Initial lizard surveys conducted in Rewanui will provide general information on the distribution of lizard populations. This will be used to determine if further monitoring is required and what actions are needed to protect lizards present. WGN_DOCS-#670192-V1 PAGE 5 OF 12 Table 1 - lizard species known from the eastern Wairarapa region and their current threat status Common Name Scientific Name Threat Status Speckled skink Oligosoma aff. Infrapunctatum “southern nationally endangered North Island” Spotted skink Oligosoma lineoocellatum gradual decline Wellington green gecko Naultinus elegans punctatus gradual decline Pacific gecko Hoplodactylus pacificus gradual decline Ornate skink Cyclodina ornata gradual decline Common skink Oligosoma nigriplantare polychroma not threatened Common gecko Hoplodactylus maculatus not threatened Forest gecko Hoplodactylus aff. granulates “southern North not threatened Island” 3. Methods This initial lizard survey was conducted from 24 November to 28 November 2008. Late November was chosen as it is a reasonably warm time of the year that normally has very few sunny days within a week. Summers in the Wairarapa can be very hot and dry and so the peak summer months were avoided as well as the cooler months of winter and autumn when lizards would be less likely to be active during the day. Dr. Marieke Lettink, a South Island based herpetologist with her own business ("Fauna Finders") specializing in reptile inventory and monitoring, was contracted to assist GW for this lizard survey. Searching was performed over four days using a number of techniques: visual and hand searching, pitfall trapping and checks of artificial retreats placed in the field five weeks earlier. Visual searching using binoculars and/or the naked eye involved looking for active or basking animals in habitats likely to be used by lizards. Most searching was done during the day, but night searching by spotlight was also conducted on one night with favourable weather conditions (refer to Table 2). Hand searching involved looking for inactive lizards within potential retreat sites (eg by carefully lifting rocks and inspecting crevices in rock outcrops, wood piles, and standing live and dead trees). Care was taken to return rocks to their previous location in so far as this was possible (any remaining lizards were gently encouraged to seek shelter elsewhere before replacing rocks). Pitfall traps (refer to Figure 1) consisted of 4.5L square plastic containers covered by plywood lids, leaving a gap small enough for lizards to enter whilst simultaneously providing captive lizards with shade and protection from predators. Pitfall traps were set in potential lizard habitat (eg talus slopes or grassy clearings) for up to three nights, baited with canned pear and checked PAGE 6 OF 12 WGN_DOCS-#670192-V1 each day. Artificial retreats consisted of 28 x 40cm sheets of Onduline (a light- weight corrugated roofing product with favourable thermal and structural properties; Lettink & Cree 2007). This design is increasingly being used in New Zealand because it is easy to implement and provides attractive shelter for a number of lizard species (eg Lettink & Cree 2007; Wilson et al 2007). Most artificial retreats were single-layered, but two-layered stacks were used in some places to increase the likelihood of detecting Hoplodactylus geckos (eg Lettink 2007; Lettink & Cree 2007). Artificial retreats were placed at 30 sites throughout the reserve five weeks earlier (on 17 and 18 October) in likely lizard habitats. Figure 1 – is a lizard pitfall trap set in Rewanui showing the plastic container in the ground with the wooden lid held above which is used to protect captured lizards from sun, rain and predators. 4. Results The weather during this week of sampling was varied with a range of conditions from windy (up to 90km/hr in exposed places) and chilly to sunny and hot, as can be often the case for late Spring in the Wairarapa (refer to Table 2). This determined the sampling methods used each day with most searching occurring in relatively sheltered habitats during the windy and cloudy days (24, 25 and 27 November). No searching was performed on 26 November as the conditions were drizzly and cool all day and into the evening. Night searching was conducted on only one night as the other nights were too cool or wet also. WGN_DOCS-#670192-V1 PAGE 7 OF 12 Table 2 – lizard survey search dates, times and environmental conditions Date Times Search Max. Temp Rain 2 Relative Av. Wind Searched Temp. (°C) 2 (mm) Humidity 1 Speed 2 (°C) 1 (%) (km/hr) 24/11/08 16:30 – 20:30 21.4 - 26.1 22.1 0 61.2– 65.5 7.4 25/11/08 Day 09:30 - 16:30 19.5– 23.6 18.4 3 52 - 67 15.1 25/11/08 Night 21:30 – 00:30 13.8– 17.8 52 - 59 26/11/08 12.5 0 4.8 27/11/08 09:30 – 16:30 11.5– 18.8 12.9 2 74 - 92 6.3 28/11/08 08:30 – 18:00 13.8– 21.0 13.5 1 61 - 87 8.9 1 As recorded with a handheld 'Kestrel 3500' weather meter. All temperatures are shade air temperatures taken at 1.3m above the ground. 2 As recorded with the Rewanui weather station displayed on the www.harvest.com website. The total number of lizards recorded in this survey is shown in Table 3. The most encountered lizard species, the common gecko, was seen in diverse habitats throughout the whole property, including rock outcrops, standing and fallen dead trees, under Onduline and in holes in live kanuka trees. The common skink was found on talus slopes (stable scree), under two Onduline tiles and rocks, and in the farmer's woodpile. Four lizards were found under the Onduline and no animals were caught in the pitfall traps. Two lizards ran away too quickly to be positively identified. A total of 61 person hours was spent searching for lizards. Appendix A provides additional capture data for the 53 lizards seen in this survey. Table 3 – total number of lizards found in Rewanui, November 2008 Lizard Species Number Common skink 6 Common gecko 45 Unidentified lizard 2 Total 53 PAGE 8 OF 12 WGN_DOCS-#670192-V1 Figure 2 – lizards found in Rewanui; left; a pregnant female common skink, right; an adult male common gecko. Most of these sites with lizards recorded single animals however, sites S03, G02, G07, G08, G09, G13 and G14 had more than one animal present in the same rocky retreat (refer to Appendix A). Rock outcrops with crevices often harboured common geckos in Rewanui and talus provided important refuge for common skinks. Figure 3 – lizard habitat in Rewanui. Left; rock outcrop habitat where the common gecko was mostly found, right; talus slope where common skinks were seen.