Denisonia Atriceps) and Mineral Exploration Within Its Range

A field observation on the Lake Cronin Snake (Denisonia atriceps) and mineral exploration within its range Harald Ehmann Biological Sciences, Sydney Institute of Technology, Broadway, New South Wales 2007 INTRODUCTION searching in the immediate and general vicinity of the tree no other epidermal fragments could The Lake Cronin Snake {Denisonia atriceps) is be found. It was suspected (but not then known from fewer than five specimens, all demonstrable) that the shedding came from a from the general vicinity of Lake Cronin (90 Denisonia atriceps. A further assessment was km east of Hyden) in the southern margin of made of the site where one live specimen was the wheat-belt of Western Australia. The taken. Most of the larger gums (salmon and a Downloaded from http://meridian.allenpress.com/rrimo/book/chapter-pdf/2644402/rzsnsw_1993_053.pdf by guest on 27 September 2021 species is considered to be vulnerable due to its rough-barked species), many of which were limited distribudon and the threat of habitat exceptionally large, had extensive trunk scarring change (Ehmann 1991). and hollows. Due to its extreme rarity there are few field data on this species, and any additional data Assessment and identification of snake may be of use in its conservation. I report here epidermis a possible significant clue to its ecology and On the basis of the single subcaudal/single draw attention to serious disregard for good anal condition of the snake shedding and its restoration practice after mineral exploration. geographic distribution (Storr et al. 1986), the Field work and observations only potential candidate species for the shedding are Denisonia atriceps, Echiopsis curta, Rhinoplo- During November 1990, I spent 24 hours in cephalus gouldii and R. nigriceps. I can exclude the general vicinity of Lake Cronin. Prior to the Rhinoplocephalus sp. because in my own arrival I had discussed the known collection considerable experience, members of this sites and behaviour of the Lake Cronin Snake genus do not chmb on near-vertical trees (or with John Dell, Greg Harold, David Knowles wood landscaping in captivity). This narrows and Steve Wilson (all of whom had field and/or the field to Denisonia atriceps or Echiopsis curta. live experience with the species). While at Lake Cronin I located the exact collecdon site of one The shapes of the ventrals and subcaudals specimen and assessed the habitat. Despite of the unknown fragment were compared to ideal warm humid evening and night-time those of preserved specimens of Denisonia conditions, no Lake Cronin Snakes were seen. atriceps, Echiopsis curta, Rhinoplocephalus gouldii, There was an abundance of potential food: R. nigericeps and also the allopatric Dendrelaphis small frogs around the Lake and small terrestrial punctulatus. These shapes are illustrated in and arboreal geckos away from the wet lake Figure 1. margin. The ventrals and subcaudals of the unknown I found a small piece of snake epidermis fragment clearly match those of Denisonia about 65 mm long, at a site 4.2 km west of the atriceps and not any of the other potentially Lake Cronin junction along the Hyden road sympatric species. There are distinct similarities and about 0.5 km north of the road. This site in the shape of the posterior edges of these is in sparse salmon gum woodland with an scales with those of the arboreal Dendrelaphis open understorey of sclerophyllous shrubs punctulatus. The latter species has a distinct growing on a sandy compacting gravelly soil. ridge at each side of the ventral surface. These The dried and slightly stretched shedding was ridges are apparent in a flattened epidermis clearly hooked up and tensioned in the dead (shedding) as a thin striation and an associated and jagged wood of an extensive tree scar slight indentadon (Fig. 1). These ridges are (partly hollowed and insect-fretted salmon known to give the snake effective grip and gum trunk) while the snake sloughed (i.e., support while climbing in situadons where while the epidermis was still moist and pliable). body contact points with the substrate are The shedding piece was at 1.5 m above the relatively few and far between. The indented ground and comprised some 45 ventrals about shape of the posterior ventral edge is also 20 single proximal subcaudals, the single anal, present in the arboreal Boiga irregularis (which and lateral body and caudal scales. Despite does not have as distinct a pair of ventral ridges). 346 Herpetology in Australia Downloaded from http://meridian.allenpress.com/rrimo/book/chapter-pdf/2644402/rzsnsw_1993_053.pdf by guest on 27 September 2021 Fig. 1. The ventral and subcaudal scales of 1) the unknown epidermal fragment, 2) Denisonia atriceps, 3) Echiopsis curta, 4) Dendrelaphis punctulatus. Note the similarities and differences in the scales' posterior (downward) margins and curvatures. 1) and 4) drawn from flattened and slide-mounted epidermal fragment (sheddings). 2) and 3) drawn from photographs of preserved specimens. The lateral parts of each scale is drawn as though flattened. The indentation is probably a functional These exploration tracks are at least 5 km structural shape associated with arboreality long, and I saw three parallel ones in the short (pers. obs.). time available. A conservadve esdmate is that the area probably has at least 280 permanently I conclude that the unknown epidermal open pitfall traps. I estimate that the holes had fragment was left by Denisonia atriceps which been drilled at least eight months before was climbing on a partly hollowed tree trunk because the hole rims and the associated spoil while still shedding epidermis. heaps had been eroded to an extent consistent In the area where the epidermal fragment with at least one rainy winter. was found and to the immediate west of the Lake Cronin Nature Reserve I found an array DISCUSSION of mineral exploradon drill holes (approxi- mately 18 cm diameter) that were deep (8 to The foregoing raises the possibility that 15 metres), and uncapped (Fig. 2). A 900 m the Lake Cronin Snake {Denisonia atriceps) sample secdon along one of several east-west may be partly arboreal. This possibility needs survey tracks had 20 drill holes of which 17 to be taken into account during the necessary were open (three had collapsed or were back- field work needed before this species' con- filled). In addition there were numerous trial servation status (vulnerable) can be con- drill holes of at least 0.5 m depth and of the firmed and the species can be effectively same 18 cm diameter. managed. Herpetology in Australia 347 Ehmann 1992), and its pugnacious yet accurate short range direct upward strike (G. Harold, S. Wilson, pers. comm.) is more in keeping with an arboreal snake than the terrestrial and aggressive Denisonia fasciata, D. maculata and D. suta all of which have a less accurate thrashing sideways strike (pers. obs.). The number and condition of mineral exploration drill holes seen is of concern. Any small animal that fell in would have litde chance of getting out of the cold water in the bottom of many of the holes, let alone climbing up the vertical walls for 8 to 15 metres. I capped as many of the holes as I could with sticks and earth. Downloaded from http://meridian.allenpress.com/rrimo/book/chapter-pdf/2644402/rzsnsw_1993_053.pdf by guest on 27 September 2021 Many other straight exploration tracks were seen in the area about 20 to 30 km either side of the Lake Cronin Junction on the Hyden road. Just how many uncapped drill holes there are in the area is uncertain, but if the number of exploration tracks is any indication there could be thousands. That these drill holes were in this condition suggests that post- exploration checks are needed. ACKNOWLEDGEMENTS I thank John Dell, Allen Greer, Greg Harold, David Knowles, Anita Peura and Steve Wilson Fig. 2. Mineral survey track near Lake Cronin with an for their generous advice and assistance, Allen uncapped drill hole in the foreground. This view is Greer (Australian Museum) for access to within 200 m of where the unknown epidermal fragment was found. The vegetation in the preserved specimens in his care, and the help- background is typical of the area, but the view does ful comments of two anonymous referees. not include a partly hollowed or dead salmon gum trunk. REFERENCES The morphology and defensive behaviour of EHMANN, H., 1992. The encyclopedia of Australian Animals: the Lake Cronin Snake also suggest partial Reptiles. Angus and Robertson: Sydney. arboreality. Its body and neck are more elongate STORR, G. M., SMITH, L. A. AND JOHNSTONE, R. E., 1986. and slender than other Denisonia or Echiopsis Snakes of Western Australia. Western Australian Museum: Perth. species (see photos in Storr et al. 1986 and 348 Herpetology in Australia .

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