Biodiversity monitoring in Rewanui Initial lizard survey for November 2008 Nyree Fea
FOR FURTHER INFORMATION Greater Wellington Regional Council Masterton PO Box 41 T 06 378 2484 F 06 378 7994 W www.gw.govt.nz
Publication date July 2009 Publication No. GW/BIO-G-09/189 File No. WB/05/05/02 ALL PHOTOS IN THIS REPORT ARE SUPPLIED BY MARIEKE LETTINK.
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.
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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 North Island”
nationally endangered
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 Island”
not threatened
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
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each day. Artificial retreats consisted of 28 x 40cm sheets of Onduline (a lightweight 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.
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Table 2 – lizard survey search dates, times and environmental conditions Date
Times Searched
Search Temp. (°C)1
24/11/08 25/11/08 Day
16:30 – 20:30 09:30 - 16:30
21.4 - 26.1 19.5– 23.6
25/11/08 Night
21:30 – 00:30
13.8– 17.8
26/11/08
1 2
Max. Temp (°C)2
22.1 18.4
Rain2 (mm)
Relative Humidity1 (%)
Av. Wind Speed2 (km/hr)
0 3
61.2– 65.5 52 - 67
7.4 15.1
52 - 59 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
As recorded with a handheld 'Kestrel 3500' weather meter. All temperatures are shade air temperatures taken at 1.3m above the ground. 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 Common skink Common gecko Unidentified lizard Total
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Number 6 45 2 53
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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.
5.
Discussion This survey provided important information on the presence and distribution of two species of lizards in Rewanui: the common gecko, and the common skink. Although other species known in the region were not encountered during this survey, the presence of these species cannot be discounted, as only a small proportion of apparently suitable habitat was searched.
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This survey did not cover all potential lizard habitat due to time and weather limitations. The four days of searching did, however, allow for an initial foray into each type of lizard habitat in Rewanui (rock outcrop, talus slope, grassland, native scrub and mature native bush). The survey proved very successful in revealing the presence and distribution of the common gecko throughout the reserve and the presence of the common skink. Visual searching was the most successful technique with most of the common geckos and skinks found this way (49 out of 53 animals). The night searching unfortunately did not reveal any forest lizard populations however, only the 'Totara Loop Track' was sampled over a three hour period. A more thorough search of the forest habitat is needed under suitable weather conditions to determine more convincingly the presence or absence of the forest gecko. As the pitfall traps did not detect any lizards, it may be assumed that common skink populations are not high in the areas sampled, as this technique is very effective for ground-dwelling skinks (M. Lettink, pers. comm.). The Onduline tiles were successful in detecting lizards on the less sunny days. With the sun out, the tiles warm quickly and can become too hot for lizards to remain underneath. Out of the 30 Onduline artificial retreat sites left out for five weeks, four lizards were seen under these which added to knowledge of lizard distribution in Rewanui. The numbers of common skink in Rewanui do not appear to be high enough to perform outcome monitoring and study their response to pest control (M.Lettink, pers. comm.). If outcome monitoring was to be performed in the future, it would be better to focus on common skinks than common geckos because they respond more quickly to management due to differences in their life-history traits. Common skinks mature more quickly (females can breed when approximately two years old versus four years in common geckos; Whitaker 1982) and have greater reproductive outputs (up to 10 babies per year; Jewell 2008, versus a maximum of two for common geckos; Cree 1994). Further lizard surveys are recommended to determine if other threatened species are present and to document the wider distributions of the common gecko and common skink. Pest animal control in Rewanui is a crucial factor in the survival of native species in this reserve. The Greater Wellington pest animals report (Fea, 2008) shows low rodent and possum numbers in July 2008 with the possum trap catch less than 1% and rat tracking index at 13.33%. A larger rodent survey (8 lines cf 6 in July) was run in October 2008 and this showed a decrease in rat abundance - 5%), with zero rats detected in the mature native bush on the western side of the property. Lizards are preyed upon by mice, rats, possums, stoats, ferrets, cats and hedgehogs and so control of these exotic species bodes well for lizards present in Rewanui. This is exciting news to find populations of common geckos and skinks and it appears that Rewanui has lizards surviving in this fragmented and diverselymanaged landscape. With continued and improved pest control it is hoped that these populations will remain secure and possibly increase in abundance and distribution.
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Annual monitoring should be continued during this three year SFF project to try to detect other lizard species known from the Wairarapa region.
6.
Acknowledgements I would like to thank the following people for their support. Tim Hewitt for his tireless and successful searching effort, Paul and Noel Hodgins for access across their stocked paddocks and Marieke Lettink for her advice during the planning stage, her expertise in locating lizards during the survey and her comprehensive feedback on the report.
7.
References Cree A. 1994. Low annual reproductive output in female reptiles from New Zealand. New Zealand Journal of Zoology 21: 351–372. Greater Wellington Regional Council Publication No. GW/BIO-G-08/144 Fea, 2008 Biodiversity monitoring in Rewanui – initial pest animal surveys July 2008 Hitchmough, R, L. Bull, and P. Cromarty (compilers). 2007. New Zealand threat classification system lists – 2005. Department of Conservation, Wellington, New Zealand. Jewell, T. 2008. A photographic guide to reptiles and amphibians of New Zealand. New Holland Publishers (NZ) Ltd., Auckland. King CM (ed.). 2005. The handbook of New Zealand mammals (2nd ed.), Oxford University Press, Oxford. Lettink, M. 2007. Comparison of two techniques for capturing geckos in rocky habitat. Herpetological Review 38:415–418. Lettink M., and A. Cree. 2007. Relative use of three types of artificial retreats by terrestrial lizards in grazed coastal shrub land, New Zealand. Applied Herpetology 4:227–243. Whitaker AH. 1982. Interim results from a study of Hoplodactylus maculatus (Boulenger) at Turakirae Head, Wellington. In: Newman DG (ed.). New Zealand herpetology: proceedings of a symposium held at Victoria University of Wellington 29–31 January 1980, pp. 363–374. New Zealand Wildlife Service Occasional Publication No. 2, Wellington, New Zealand. Whitaker AH. 1987. The roles of lizards in New Zealand plant reproductive strategies. New Zealand Journal of Botany 25: 315–328. Wilson DJ, Mulvey RL & Clark RD. 2007. Sampling skinks and geckos in artificial cover objects in a dry mixed grassland-shrub land with mammalian predator control. New Zealand Journal of Ecology 31: 169–185.
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Appendix A Catch data for lizards captured in Rewanui S = common skink, G = common gecko, UL = unidentified lizard, SVL = Snout to Vent length (mm), TL = Tail Length (mm). ID S01 S02 G01 G02 G02 G02 G02 G02 G02 G02 G03 G04 S03 S03 G05 G06 G07 G07 G07 G07 S04 S05 G08 G08 G09 G09 G10 G11 G12 G13 G14 G15 G16 G17 G18 G19 G20 G21 UL01 UL02
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SVL 41 63 68 50 48 55 55 58 40 not captured 36 57 61 not captured 54 not captured 39 57 38 38 not captured 68 37 2 not captured 36 32 71 not captured not captured 3 not captured 11 not captured 67 not captured 48 not captured not captured 72 not captured not captured not captured
TL 43 67 50 55 54 64 65 63 50 38 74 80
Regen 3 21 43
Sex / Status Juvenile Female Pregnant Male Juvenile Juvenile Juvenile Juvenile Juvenile Juvenile Adult
15
63 46 25 44 44 77 40
19
5
42 35 90
80 Juvenile 58
76
Female Pregnant
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