Research Report Canid predation: a potentially significant threat to relic populations of the Inland Carpet Python Morelia spilota metcalfei (Pythonidae) in Victoria Geoffrey W Heard1-*,Peter Robertson3, Dennis Black', Geoffrey Barrow', Peter Johnsons, Victor Hurley6 and Geoffrey Allen6 'Department of Environmental Management and Ecology, La Trobe University, Albury-Wodonga Campus, PO Box 821, Wodonga, Victoria 3689 'Current Address: Department of Zoology, La Trobe University, Bundoora, Victoria 3086. Email: [email protected] 'Wildlife Profiles Pty. Ltd., PO Box 500, Heidelberg, Victoria 3084 'Parks Victoria, Tara Crt, Ford Street, Wangarana, Victoria 3677 'Department of Sustainability and Environment, North-west region, PO Box 3100, Bendigo Delivery Centre, Bendigo, Victoria 3554 Tlora and Fauna Business, North-west Region, Department of Sustainability and Environment, PO Box 905, Mildura, Victoria 3500 Abstract In Victoria's contemporary rural environments, introduced predators may represent the principal predatory threat to many large, non-venomous reptile species. We present circumstantial evidence that introduced canids are predators of the Inland Carpet Python Morelia spilota metcalfei, using data collected during a radio-telemetric study of the sub-species' ecology across northern Victoria. Seven pythons (23% of those tracked) were killed by predators during the study, and evidence col- lected during transmitter retrieval suggested that foxes or wild dogs were involved in six of these cases (the seventh having been eaten by a goanna). Evidence includes the recovery of transmitters from fox den sites, their partial burial in several cases (consistent with caching behaviour) and dam- age to each transmitter consistent with chewing by a fox or dog (teeth marks in the silicon coating, puncture of the metal housing). Given the abundance of canids (specifically foxes) within these study sites, their ability to prey on carpet pythons, and evidence of their involvement with these pre- dation events, we conclude that canid predation was the primary cause of death for each of these six snakes, and represents a potentially significant issue for carpet python conservation in Victoria. Suggestions for canid control programs and habitat management to minimise this threat to remaining populations of this endangered snake are offered. (The P"ctorian Naturalist 123 (2) 2006. 68-74) Introduction The Inland Carpet Python Morelia spilota omous, and inhabits inland regions of metcalfei (Pythonidae) is a large (to 3 m southern Australia where introduced preda- total length), semi-arboreal snake that is tors can be abundant and ubiquitous across distributed widely across the Murray habitats (Newsome et al. 1997). Darling Basin of south-eastern Australia In this paper, we present circumstantial (Barker and Barker 1994; Greer 1997). In evidence that these pythons are vulnerable Victoria, the sub-species is considered to predation by introduced canids (primari- endangered (DSE 2003) and restricted to ly the Red Fox V~rlpesv~rlpes but potential- the woodland habitats of the northern ly also Wild Dogs Canis familiaris). plains, primarily those associated with Specifically, we detail evidence that canids watercourses (River Red Gum Euca/,~ptzrs killed the majority of carpet pythons lost to camald~rlensisor Black Box E. Iarg~jlorens predation during a radio-telemetric study woodland) or prominent granite outcrops of the sub-species' ecology conducted (Coventry and Robertson 1991 ; Allen et al. across Victoria's northern plains between 2003). Apparent declines in the sub- 1997 and 2002. species' Victorian range have been attrib- Methods uted primarily to habitat alterations; how- Stirr!~.areas ever, predation by introduced mammals has Pythons were radio-tracked in nine study also been cited as a potentially threatening areas, spanning three regions of northern process (Allen et al. 2003). This snake may Victoria (Fig. I). In the north-east, 17 be particularly vulnerable to exotic preda- snakes were tracked in three study sites tors; it is relatively slow moving, non-ven- 68 The Victorian Naturalist Research Report Fig. 1. The location of each study area in which carpet pythons were radio-tracked across northern Victoria. Study areas are: 1 - Mt Killawarra, 2 - Boweya, 3 - Mt Bruno, 4 - Mt Meg Flora and Fauna Reserve, 5 - Mt Hope Flora and Fauna Reserve, 6 - Nyah State Forest, 7 - Piambie State Forest, 8 - Lambert Island, 9 - Walpolla Island State Forest.. either within, or adjacent to, the Warby dominated by Deane's Wattle Acacia Range State Park, including Mt Killawarra deanei paucijuga (Conn 1993; Parks (36O15'N, 146O1 I'E), Mt Bruno (36OI9'N, Victoria 2000). 146O09'E) and Boweya (36O 1 7'N, Eight pythons were radio-tracked within 146O09'E). An additional study site, the Mt the Riverine forests of north-western Meg Flora and Fauna Reserve (36O22'N, Victoria. From east to west, snakes were 146O05'E), is located in the Chesney Vale tracked at Nyah State Forest (35O05'N, Hills, 22 km WSW of the Warby Range. 143O20'E), Piambie State Forest (34O52'N, All areas within the north-east are charac- 1430201E), Lambert Island (34O2 I'N, terised by steep, rocky slopes (weathered 142O22'E) and Walpolla Island State granite outcrops and screes) with open Forest (34O07'N, 141°42'E). All sites were granitic woodland or low heathland. At all located on the floodplain of the Murray locations, remnant vegetation abuts cleared River. Vegetation composition varied little agricultural land, with the extent of frag- between the three localities, being domi- mentation being highest at Mt Meg, where nated by River Red Gum and Black Box. a mosaic of remnant vegetation occurs Disturbance from cattle grazing, timber (Heard and Black 2003; Heard et al. 2004). extraction and recreational activities are Five pythons were radio-tracked within common to all localities. the ~i Hope Flora and Fauna Reserve (35059fN, 144013tE)in north-central St~idj'aninzals and radio-telenzetric Victoria. Mt Hope is a prominent granite "lonitoring massif that rises steeply from the Temperature-sensitive. miniature radio ing plains, most of which have been transmitters (Holohil Systems Pty Ltd, cleared for agriculture, The reserve sup- Canada; S1-2T) were ports a shrub-land vegetation community implanted within the body cavity of snakes Research Report under aseptic conditions. A description of sheltering within a rock crevice. Its trans- implantation techniques is provided in mitter was subsequently located within an Heard et al. (2004). Units represented less open paddock east of this site, partially than 2% of python body weight in all cases. buried in the soil, with numerous teeth We endeavoured to locate each python marks in the unit's silicone coating. weekly (usually in the morning to early The remaining two snakes lost in the afternoon). However, logistical constraints north-east were both apparently killed occasionally resulted in this interval being within the vicinity of residential buildings. reduced or extended between 2 and 21 At Mt Meg, 'NE16' was last recorded days. A directional 'H' antenna and minia- inhabiting a roof cavity within a series of ture radio receiver (Telonics Inc., Arizona) buildings in the south of the study site. The were used to track the signal of radio trans- snake had occupied these buildings during mitters, and co-ordinates of each location all locations in the two months following were recorded in the Universal Transverse her re-release, and thus appeared to have Mercator (UTM) system using a Trimble been taken during her first movement global positioning system (Trimble 10 away from the buildings during the track- channel Ensign XL GPS Unit). ing period. Her transmitter was subse- Upon the death of a python, notes were quently located lying on the ground in an maintained on the location of the carcass open paddock east of this site. The unit had or transmitter, and descriptions of the sur- been bitten repeatedly, exposing its metal rounding habitat and specific collection casing. At Mt Bruno, an immature female site recorded. The identity of any predator 'NE15' was killed after residing for sever- involved was assessed by damage to trans- al months in the vicinity of a residential mitters (including teeth marks), collection building located in remnant woodland. site characteristics and the presence of This snake was also last found inhabiting a scats or footprints. roof cavity. Its transmitter was retrieved from a wooded slope overlooking the Results property; it had been chewed and partially Seven carpet pythons (23% of those buried. tracked) were killed during the study, five One python was killed at each of the Mt in the north-east and one each at Mt Hope Hope and Piambie study sites (Table I). At and within the riverine forests of the north- Mt Hope, the dismembered remains and west (Table 1). One of these animals transmitter of the large, adult female 'NEI I' apparently fell victim to a Lace 'NW31' were found at the entrance to a Monitor Varanus varius; the transmitter rock crevice on 4 May 1999. The snake was located within a tree-hollow some four had been recorded within this rock crevice metres above ground amongst numerous during the previous two tracking events goanna scats. However, evidence collected (25 March, 14 April 1999). and had fre- during transmitter retrieval suggests that quented the site during the months preced- canids killed the remaining six pythons. ing death. This snake had been tracked for Two animals were killed in remnant 565 days in total. Lastly, the Piambie ani- woodland at Mt Meg. The first, 'NE13', mal 'NWOI' was apparently killed whilst died within 16 days of release. Prior to inhabiting a large, relatively open hollow death, this animal was recorded sheltering log in River Red Gum woodland. The par- in a hollow log amongst intact remnant tially chewed transmitter (numerous teeth woodland on the north face of Mt Meg. marks were evident in the silicone coating) The heavily chewed transmitter from this from this snake was located approximately snake was located within a fox den in 50 m from this log, beneath loose woody dense shrubbery amongst the remains of debris.