Survey of the underground signs of marsupial moles in the WA Great Victoria Desert Report to Tropicana Joint Venture and the Department of Natural Resources, Environment and the Arts, Northern Territory Government Joe Benshemesh Martin Schulz September 2008 Marsupial moles in the WA Great Victoria Desert Benshemesh & Schulz 2008 Contents Summary.......................................................................................................................3 Introduction..................................................................................................................5 Methods........................................................................................................................7 Methods........................................................................................................................8 Sites.........................................................................................................................8 Trenches.................................................................................................................9 Moleholes ..............................................................................................................9 Additional data ....................................................................................................9 Results..........................................................................................................................12 Characteristics attributes of backfilled tunnels in WA GVD.............................12 Size and shape of backfilled tunnels...............................................................12 Depth of backfilled tunnels...............................................................................15 Age of backfilled tunnels ..................................................................................16 Abundance of moleholes ....................................................................................18 Trench drying time .............................................................................................18 Topography.........................................................................................................19 Geography .........................................................................................................19 Habitat features..................................................................................................20 DISCUSSION ................................................................................................................22 Occurrence of marsupial moles in the WA GVD ..............................................22 Undersized moleholes........................................................................................23 Marsupial moles distribution and abundance in GVD .....................................23 Final comments......................................................................................................25 References..................................................................................................................26 Appendix 1 .................................................................................................................27 Appendix 2. Incidental fauna records ...................................................................30 2 Marsupial moles in the WA Great Victoria Desert Benshemesh & Schulz 2008 Summary • Itjaritjari (Southern Marsupial Mole Notoryctes typhlops) and its close relative the Kakarratul (Northern Marsupial Mole N. caurinus ) from north-western Australia, are little known subterranean animals that inhabit the vast sandy deserts of Central Australia. Elusive, enigmatic, and the sole representatives of a unique and ancient lineage, these animals are rarely encountered and both species are listed as Endangered nationally. • Although the Great Victoria Desert (GVD) is a major stronghold for Itjaritjari, there are few records of the species from the Western Australia side of the desert. The distribution, abundance and trends of the species in the WA GVD are uncertain. • The current study was undertaken to provide new information on the distribution and abundance of Itjaritjari in the WA GVD in order to assess the conservation status of the species across this land system. • Between the 28th April and 14th May 2008, we surveyed a broad range of potential habitats in the WA GVD using trench survey techniques to assess the abundance of Itjaritjari signs underground. The survey sampled a small but representative proportion of the potential Itjaritjari habitat within the WA GVD landscape • Thirty five sites were sampled at which a total of 89 trenches were excavated. Over 170 backfilled tunnels were recorded in these trenches and at least 95% of these tunnels were considered to have been made by Itjaritjari. • Moleholes were typically 40 mm in diameter (standard deviation: +/- 3mm) and were similar in every way to those previously measured in the Anangu-Pitjantjatjara-Yankunytjatjara Lands in South Australia (SA) where the identity of backfilled tunnels of about 40mm has been linked to Itjaritjari tracks on the surface, and with the tunnels made by Itjaritjari that were captured and later released. • The results of the survey indicate that the species still occurs in the WA GVD and that it is widespread and probably more common than previous records suggest. Molehole abundance was similar to that recorded in the SA GVD and suggested that more than 30 km of recognisable moleholes per hectare occurs on the crests and slopes of these dunefields. However, we were unable to estimate the population size as the rates of decay and creation of moleholes is still uncertain. Studies are underway to estimate these quantities; however results are still several years away. • About 10% of moleholes we recorded appeared fresh, indicating that that Itjaritjari have created an average of about 3 km of backfilled tunnel per hectare since the last soaking rains at the 27 sites at which moleholes were identified in this study. • We also found that the abundance of moleholes in trenches was strongly related to the hardness of the sand, the height of dunes, the position of a trench on a dune, and the degree of connectivity between dunes. 3 Marsupial moles in the WA Great Victoria Desert Benshemesh & Schulz 2008 • The sensitivity of Itjaritjari to the connectivity between dunes suggests that the species may be especially vulnerable to any changes in the configuration and connectivity of dunes that result in patches of dunes being cut off and isolated from the surrounding dunefield matrix. Thus, earthworks that disrupt dune connectivity and effectively fragment Itjaritjari populations could cause more damage to Itjaritjari than the footprint of earthworks might suggest. It would be prudent for earthworks to proceed only with careful consideration of their likely effects on the continuity of Itjaritjari populations, and in conjunction with strategic survey and monitoring of Itjaritjari populations in the area. 4 Marsupial moles in the WA Great Victoria Desert Benshemesh & Schulz 2008 Introduction Marsupial moles ( Notoryctes typhlops and N. caurinus ) are little known subterranean animals that inhabit the vast sandy deserts of Central Australia. Elusive, enigmatic, and the sole representatives of a unique and ancient lineage, these species are rarely encountered and are listed as Endangered nationally, although even this is uncertain due to the paucity of information available about their population trends and ecology (Benshemesh 2004). Direct examination of marsupial mole ecology is virtually impossible with current techniques due to the apparent rarity of the animals and their cryptic subterranean habits, and conventional trapping methods such as the use of Elliot traps or pitfall traps are ineffective for detecting the presence of this species. However, recent studies in the Anangu-Pitjantjatjara-Yankunytjatjara Lands (APYL) have shown that indirect methods provide a means for examining the distribution and abundance of marsupial moles (Benshemesh 2005a). These methods include searching for the underground signs of marsupial moles which provides information on distribution and an index of abundance, and collecting and examining predator scats that occasionally contain marsupial moles remains and DNA and thus provides information on which species occurs in an area. Given that both species of marsupial moles are currently listed as Endangered under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999 , data on the distribution and abundance is urgently needed both to assess the current status of the species, and to provide benchmarks for subsequent monitoring. The Great Victoria Desert (GVD) straddles the Western Australia (WA) and South Australia (SA) border and is the largest sand dune desert in Australia totalling nearly 40 million hectares. The WA side of the GVD comprises over 20 million hectares and is characterized by vast sand dune habitat that extends from the Nullarbor Plain in the south to the Central Ranges and Gibson Desert in the north (Figure 1). The region stretches from Laverton in the west to the South Australian border in the east, and most of this vast expanse is dunefield habitat. Itjaritjari (Southern Marsupial Mole N. typhlops ) have been collected or observed a number of times in the GVD and there are 52 records from this bioregion (including immediate surrounding areas) in museums and wildlife atlases around Australia