Herpetofauna of the Southern Carnarvon Basin, Western Australia

DOI: 10.18195/issn.0313-122x.61.2000.335-360 Records of the Western Australian Museum Supplement No. 61: 335-360 (2000). Herpetofauna of the southern Camarvon Basin, Western Australia 2 2 2 N.L. McKenziet, J.K. Rolfet, K.P. Aplin , M.A. Cowan and L.A. Smith 1 Department of Conservation and Land Management, p.a. Box 51, Wanneroo, Western Australia 6065, Australia 2 Western Australian Museum, Francis Street, Perth, Western Australia 6000, Australia Abstract - We sampled the frog and reptile species on 63 quadrats chosen to represent the geographical extent and diversity of terrestrial environments in a 75 000 km2 study area in the Carnarvon Basin. Twelve frog and 17 gecko, 10 pygopodid, 16 dragon, 58 skink, four goanna and 16 snake species were recorded, an average of 16.3 species per quadrat. Patterns in species composition were related to biogeographical, ecological and local evolutionary processes. Four species assemblages were distinguished, each relating to gradients in a different set of precipitation plus soil plus topographic attributes. In these terms, Poisson error models with logarithmic links fitted the relationships. Virtually identical patterns emerged when we re-analysed the data using an ecological taxonomy that was based on functional morphology. If evolutionary processes are to be protected along with the ecological and biogeographical processes, the reserve system will need to sample the geographical range of the various rainfall, soil and topographic gradients identified by the analyses. INTRODUCTION patterns in the study area was carried out by This study explores patterns in the composition of Kendrick (1991), for his dissertation on the reptilian and amphibian communities in non- biogeography, ecology and systematic aquatic environments of the southern Carnarvon relationships of the skink genus Lerista. But the Basin. lack of any systematic ecological survey of the The earliest records from the study area were made entire herpetofauna in terms of the study area's early last century by naturalists Peron, Quoy and climatic and, geomorphological gradients has Gaimard accompanying the French navigators precluded any quantitative understanding of the Baudin and Freycinet (Storr and Harold, 1978). The structure and composition of this component of its German zoologists W. Michaelsen and R. Hartmeyer communities. made the next collections in 1905 (Werner, 1909). By sampling a set of quadrats, positioned to Most of the data available at the outset of this represent the diversity of the study area's physical study were derived from specimens collected in the environments across its geographical extent, we area since the 1950s and lodged in the collections of aimed to provide a regional context for conserving the Western Australian Museum. Sources included the study area's herpetofauna. Specifically, our the localised inventories of Bernier and Dorre Island objectives were to: (Douglas and Ride, 1962), Faure Island in 1959 • carry out the first systematic survey of species (W.H. Butler, unpublished), Dirk Hartog Island extant in the study area, (Burbidge and George, 1978), Edel Land and • lodge voucher collections in the Western Hamelin (see Storr and Harold, 1978), and Toolonga Australian Museum for detailed taxonomic Nature Reserve (Burbidge et al., 1980). appraisal (Aplin et al., in press), The first comprehensive inventories, carried out • provide an overview of the status and between 1976 and 1980 by Harold, Peterson and distribution of species, Winton, allowed Storr and Harold (1978, 1980, • describe the relationships between species 1984) to review the biogeographical relationships occurrences and attributes of the study area's and habitat-preferences of the amphibian and physical environment, and identify predictors of reptilian species known from the Zuytdorp, Shark gradients in species composition across the Bay and Lake MacLeod Regions. Combined, these study area and three regions cover the same tract of country as our • provide a quadrat-based benchmark against study area. which future changes in the status of the The first quantitative sampling of herpetofaunal herpetofauna can be measured. 336 N.L. McKenzie, J.K. Rolfe, K.P. Aplin, M.A. Cowan, L.A. Smith ~(~;> ... ~,;~,:r.... 113° 24° 24 Bernier 1 25° Donel Dirk Hartog 1 ~ N 27° 0 25 50 Kilometres 'J. ;; .-- t- ~ Cl ;: 114° c. 0 ...~. :> 0 )/, Figure 1 The Camarvon Basin study area, showing the 13 survey areas (campsites) and individual quadrat positions. Precise quadrat co-ordinates are provided in Appendix A (p. $$$, this volume). Survey area codes were Bush Bay (BB), Boolathana (BO), Cape Cuvier (CD), Edel Land (EL), Gascoyne Junction (GJ), Kennedy Range (KE), Meedo (MD), Mardathuna (MR), Nanga (NA), Nerren Nerren (NE), PelOn Peninsula (PE), Woodleigh (WO) and Zuytdorp (ZU). Herpetofauna 337 METHODS the coast southwards from Shark Bay is partially mantled by palE yellow to grey sands supporting Study Area low proteaceous heaths with r ~ thickets of The Carnarvon Basin study area covers 75 000 Banksia and mallees such as Eucalyptus illyarrie. km 2 on Australia's western coast. It is centred on White coastal sand dunes support Spinifex longifolius Shark Bay, and extends northwards from the communities. Low-lying saline areas, such as the Murchison River to the Minilya River, and fringes of Lake MacLeod and the coastal flats, eastwards to 115°30'E (beyond Gascoyne Junction) support samphire and saltbush communities. (Figure 1). Detailed descriptions of the vegetations in the study Its physical environments are detailed by Wyrwoll, area are provided by Beard (1975, 1976), Payne et al. Courtney and Sandercock (2000) and Wyrwoll, (1987), Gibson et al. (2000) and Keighery et al. (2000). Stoneman, Elliott and Sandercock (2000). Briefly, the region is alow land characterised by gentle gradients Historical Review on abasement of soft sediments. Under avariety of climates, interacting alluvial and aeolian processes Lists of the species previously captured in the study area were extracted from published literature have produced acomplex landscape mosaic, that has and from the Western Australian Museum's been further modified by extensive coastal transgressions associated with sea-level changes. zoological register. Today, the area south of Shark Bay has asemi-arid climate influenced by temperate weather systems Field Sampling (mainly winter rainfall). From Shark Bay northward, Herpetofauna were sampled on quadrats the climate is influenced by both tropical and positioned throughout the geographical extent of temperate systems; semi-arid at the coast, but arid the study area in astratified random array. The with locally unreliable summer and winter rainfall quadrats were placed in typical examples of each of further inland. In phytogeographic terms, the study the surface stratigraphic units that characterise the area comprises the northern half of the Irwin District study area. Many quadrats were pseudo-replicated of the South-western Province, as well as the (locally as well as at distant points) to allo'Y for the southern half of the Carnarvon District of the internal heterogeneity of the stratificatton units Eremean Province (Beard, 1980). (hypothesised scalars) and to. ~ any Extensive alluvial plains dominate the study area, analytical circularity introduced by the stratification although erosional uplands such as the Kennedy (McKenzie et al., 1989, 1991b). Range occur in its eastern parts. The plains are The study area encompassed seven million traversed from east to west by two large, ephemeral hectares, and sampling was restricted to 63 releve rivers: the Gascoyne and Wooramel. Both rivers are quadrats with acombined area of 1008 hectares lined with groves of River Gum (Eucalyptus victrix). (each releve was set in avisually homogeneous 400 Low open woodlands of bow gad a(Acacia linophylla) x400 m area =16 hectares; 63 x16 =1008 ha). Thus, and snakewood (A. xiphophylla) over Atriplex, Senna sampling was sparse; no more than 0.014% of study and Eremophila shrubs and tussock grasses cover the area was actually sampled. The 63 quadrats were plains, with Acacia grasbyi in areas where calcretes clustered in sets of two to six quadrats around each are exposed. Low red sand ridges scattered across of 13 survey areas, herein referred to as 'campsites'. the plains support shrubs over mainly hummock- Trapping and hand-foraging (digging, raking etc) grasses. In northern parts, the plains grade into red were used to detect species' presence-absence on sand dune fields that support hummock-grass and quadrats. Two pitfall-trap arrays were placed on mulga (A. aneura) communities reminiscent of the each quadrat. The arrays each comprised aline of 6 red centre. In the south the plains support PVC tubular pitfall-traps ('tubes'), 125 mm in woodlands of Eucalyptus loxophleba and Callitris diameter and 500 mm deep, spaced at 10 m glaucophylla, with mallee, Banksia, Allocasuarina and intervals along a50 m flywire drift fence that was Actinostrobus scrubs and heaths on greyish and 300 mm high. About 5 m from either side of the 50 yellow sand dunes. Astrip of limestone that follows m fence was a"bucket" pitfall-trap 300 mm in Table 1 Total number of fenced pitfall-trap nights per sampling session, excluding the 9260 tub-nights in May 1995. Pit-trap Type Oct94 Jan 95 May 95 Nov 95" Mar96 b Total Buckets 1220 12 1244 2476 Tubes 3660 72 3704 516 2736 10 688 Total 4880 84 4948 516 2736 13164 "see 'Data quality', below. bsee Table 2. 338 N.L. McKenzie, J.K. RoUe, K.P. Aplin,

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