Mammals of the Lower Sullivans Creek Catchment, Canberra ACT
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Mammals of the Lower Sullivans Creek Catchment, Canberra ACT Prepared by: Christopher R. Tidemann, Toby J. Roscoe School of Resources, Environment and Society, and Beth Mitchell Energy and Sustainability Office (ANUgreen) The Australian National University Canberra, ACT 0200 A report prepared for the Life in the Suburbs project using data from the Lower Sullivans Creek Ecological Survey (LSCCES) September 2006 Summary The Lower Sullivans Creek Catchment is a diverse area that presently supports thirty four species of mammals: two monotremes - both native, nine marsupials - all native, thirteen bats - all native, four rodents - two native, three carnivores – all introduced and two lagomorphs – both introduced (ACT Vertebrate Atlas; C.R. Tidemann, unpublished data). Two bats occasionally recorded from the area have special conservation status: the Grey-headed Flying-fox (Pteropus poliocephalus) is nationally Vulnerable (Environment Protection and Biodiversity Conservation Act 1999) and the Bent-winged Bat (Miniopterus schreibersii) is listed as Rare in the ACT. Several mammals have disappeared from the LSCC following European settlement, including the Koala, (Phascolarctos cinereus) and Tiger Quoll (Dasyurus maculatus). Some introduced mammals are classified as pests, e.g. Foxes (Vulpes vulpes), Rabbits (Oryctolagus cuniculus), and Mice (Mus domesticus). Introduction Shielding vulnerable species from the detrimental impacts of urbanisation including habitat destruction, fragmentation and simplification, and unnatural selection pressures such as predation and competition from introduced species is essential to the conservation of biodiversity. This enables natural ecological processes to provide the resources required to maintain a healthy mammalian diversity component. Successfully incorporating the protection of existing ecological communities, creating areas for ecological restoration and implementing integrated, humane and socially acceptable control measures for Invasive Alien Species (IAS) is essential to sustaining healthy populations of mammals in the Lower Sullivans Creek Catchment (LSCC). While statutory regulations currently require development plans to identify and moderate impacts on biodiversity and environment quality, the capacity of such mechanisms to preserve biodiversity assets within urban landscapes is often negligible. In an urban context, the value of these assets is typically underestimated and as such is seldom acknowledged within assessment and planning frameworks. In addition, the impact of existing developments and their landscapes on biodiversity assets goes largely unchecked despite the potential for these landscapes to harbour serious threats to both local and regional biodiversity, such as IAS. To ensure the Mammal Report for the Lower Sullivans Creek Catchment Ecological Survey 2 September 2006 maintenance and enhancement of urban biodiversity, the identification and protection of these assets must be incorporated into development plans as well as mainstream management practices. At present there are few precedents that incorporate such management principles. This report aims to survey the status of mammals in the LSCC and to highlight management goals to preserve their abundance and diversity within the urban sub- catchment. The analysis provides an assessment of data collected in the LSCC and incorporates knowledge of the site garnered through previous work conducted within the sub-catchment by the authors and by others. Methodology Prior to the commencement of mapping and permit acquisition, three assessment techniques were proposed: spotlighting, to detect large and particularly arboreal mammals, small mammal trapping using Elliot traps, and sand plots, to capture the tracks of medium sized mammals. Survey design for baseline data collection was limited to spotlighting due to resource requirements and the logistical difficulty of implementing other survey techniques with predominantly volunteer labour. Survey design, protocols and datasheets for mammal spotlighting were adopted from the Great Australian Marsupial NightStalk initiative run through Perth Zoo and the Marsupial Cooperative Research Centre. Protocols were adapted to include provisions for vehicle safety, in addition to tenant privacy in residential and campus zones. Datasheets were adapted to include a list of species likely to occur in the study site, with generic information for each season included to promote standardisation. Site selection was restricted by the practical difficulties of spotlighting in close proximity to vehicles, with no sites being designated in the Central Business District (CBD). Volunteer safety was also a major consideration in the selection of sites, with areas of dangerous terrain avoided and transects sited predominantly along predefined paths, including cycle paths and walking tracks. Thirteen one kilometre transects were mapped across a diversity of land uses to reflect potential habitat types across the study area. Transects were marked with reflective tape to guide surveyors and ensure consistency of survey transects across seasonal surveys. Map 1 shows the geographic location of transects in relation to infrastructure and landscape components. Mammal Report for the Lower Sullivans Creek Catchment Ecological Survey 3 September 2006 Map 1. Spotlighting transects Mammal Report for the Lower Sullivans Creek Catchment Ecological Survey 4 September 2006 Teams of 2 to 4 people, including one team leader with experience in surveying mammals, surveyed the abundance and diversity of mammals across the thirteen transects, with each team surveying two transects over a one-hour period. Observations were made through visual detection, with notes of macropod movement and bird and bat calls also recorded. Surveys were scheduled to coincide with the new moon in the last month of spring, summer and autumn, with surveys being conducted on the 4th of November 2002, 1st of February 2003 and the 1st of May 2003. All 13 sites were surveyed in the spring survey, with 12 and 10 sites respectively being completed in the summer and autumn surveys. Lack of experienced surveyors to lead volunteers led to the reduction in sites surveyed in these instances. Findings Ten mammal species were recorded along spotlight transects in the LSCC. Table 1 highlights these species and includes the thirty-four species known to occur in the study area, their country of origin and their conservation or pest status under Commonwealth and ACT legislation. It is acknowledged that employing only one survey technique, spotlighting, targeted a specific mammal group, being larger mammals. Table 2 indicates the habitat preference of species known to occur in the study site and illustrates the diversity of survey techniques required to comprehensively survey their presence. The use of more sophisticated mammal survey techniques, including sand- trapping and cage-trapping of ground mammals and ultrasound detection of microbats, would provide a more accurate indication of the number of species that use the site. Implementation of these techniques would also help maintain volunteer interest, but would require training of volunteers, ideally through intensive workshops to ensure the accuracy of data and use of appropriate protocols. The implementation of these techniques would require a stable support group of experts to guide survey conduct and to ensure adherence to protocols, particularly with regard to trapping exercises. The cost in human hours and resources to achieve this would be considerable, however, findings would provide a significant contribution to the understanding of urban landscape use by mammals and also in monitoring the success of management actions. Mammal Report for the Lower Sullivans Creek Catchment Ecological Survey 5 September 2006 Of the mammals recorded in the LSCC, Common Brushtail Possums (Trichosurus vulpecula) and Ringtail Possums (Pseudocheirus peregrinus) are the most abundant native species (Chart 1). The two species are from the same taxonomic family and both are medium sized herbivorous arboreal mammals. To some extent, Brushtail and Ringtail Possums require similar resources from their habitat, though Brushtails were typically more common in built up areas - one would expect this to be the case considering their ability to utilise human dwellings for nesting sites, and to fend off domestic predators such as cats. Ringtail Possums occurred less frequently in built up areas, preferring wooded sites within the study area. Nevertheless, LSCCES data demonstrates that populations of ringtail possums increased sharply between spring 2002 to autumn 2003, while over the same period the population of Common Brushtail Possums declined (Chart 2). This is likely to be a consequence of inter-seasonal behavioural differences between the two species, or may represent a long-term change in the relative abundance of the two species. Severe drought conditions and extensive wildfires in the surrounding region in January 2003 may also have influenced the visibility of Ringtail Possums between the two seasons. Mammal Report for the Lower Sullivans Creek Catchment Ecological Survey 6 September 2006 Table 1. Mammals recorded from the Lower Sullivans Creek Catchment, showing type, country of origin, conservation status and whether the species was recorded on the survey. Recorded on Common Name Scientific Name Type Origin Status survey? House Mouse Mus domesticus Rodent Asia Gould's Wattled Bat Chalinolobus gouldii Bat Australia Chocolate