Kowari Monitoring in Sturts Stony Desert 2009
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Government of South Australia South Australian Arid Lands Natural Resources Management Board May 2009 South Australian Arid Lands Natural Resources Management Board Kowari monitoring in Sturt’s Stony Desert, SA Reece Pedler DISCLAIMER The South Australian Arid Lands Natural Resources Management Board, and its employees do not warrant or make any representation regarding the use, or results of use of the information contained herein as to its correctness, accuracy, reliability, currency or otherwise. The South Australian Arid Lands Natural Resources Management Board and its employees expressly disclaim all liability or responsibility to any person using the information or advice. © South Australian Arid Lands Natural Resources Management Board 2009 This work is copyright. Apart from any use permitted under the Copyright Act 1968 (Commonwealth), no part may be reproduced by any process without prior written permission obtained from the South Australian Arid Lands Natural Resources Management Board. Requests and enquiries concerning reproduction and rights should be directed to the General Manager, South Australian Arid Lands Natural Resources Management Board Railway Station Building, PO Box 2227, Port Augusta, SA, 5700 INTRODUCTION Monitoring of the Kowari (Dasycercus byrnei) population on Clifton Hills Station has been ongoing over the last 9 years following early work in the far north of South Australia and south- west Queensland in the 1990’s. Two monitoring grids were established on Clifton Hills Station by Department for Environment and Heritage in areas that were thought to represent ideal habitat for the species with the aim of comparing numbers between different intensities of cattle grazing and monitoring Kowari numbers over time. The grids near Pandiburra Bore (Pandiburra Grid) and Gap Paddock (Walker’s Crossing Grid) each consist of 200 Elliot (aluminium box) traps which are spaced at 100 m intervals in five 4 km lines. The last time that a full trapping session was conducted on these grids was in March 2006. Since this time, a survey of major Kowari populations in South Australia was carried out in Spring 2007 on neighbouring pastoral properties to determine the status of the Kowari during a prolonged period of drought. This survey failed to detect any Kowaris and it was feared that they may be absent from these areas. Some additional opportunistic trapping was subsequently carried out on the Walker’s Crossing Grid in Gap Paddock and around Blue Motor Car Dam on Pandie Pandie Station in late 2007 by Reece Pedler and John Read and found encouraging numbers of young Kowaris. The aim of the current trapping was to check on the numbers of Kowaris remaining in these areas by comparing the numbers trapped with earlier monitoring sessions and to assess attributes of habitat relevant to Kowaris. Revisiting the area also allowed some opportunistic trapping in an area to the south of the monitoring grids that appeared to represent appropriate habitat based on satellite imagery. METHODS Fieldwork was conducted by Peter Canty, Robert Brandle, Alex Clarke and Reece Pedler. The two permanent monitoring grids established in areas of open gibber at Pandiburra Bore and in Gap Paddock were opened simultaneously for 4 nights from 11th -15th May 2009. Each grid consists of an array of 200 metal box traps (Elliot Type 2) set in five 4 km lines of 40 traps with 100 m spacing between each trap. Grids covers a minimum area of 16 km2 as each line is separated by 1 km, but a total area of 26 km2 includes a 500 m buffer around the grid. Traps were set for four nights at each grid. The Walker’s Crossing or ‘WAL’ Grid (in Gap Paddock) samples an area of gibber, swamp and dune in an area remote from a stock watering point with light levels of grazing. Pandiburra Paddock or ‘PAN’ Grid is positioned close to Pandiburra Bore, which has had historically moderate to high levels of grazing. The grids are approximately 30 km apart in the Koonchera Dune area on Clifton Hills Pastoral Lease (Figure 1). Kowaris were trapped using Elliot traps baited with tuna oil soaked dog biscuits and peanut butter and rolled oats mixture. Each animal captured was given a unique temporary marking with a coloured paint combination on the tail, allowing animals recaptured within the same trapping session to be identified. Each animal captured was weighed, measured and released back at its point of capture. Four established vegetation monitoring transects on PAN GRID and six on WAL GRID were resampled. Sampling involved 300 consecutive wheel-point measurements in vegetated areas of specific habitat types. Series of sand mounds on gibber, also sampled for vegetation cover, were monitored for signs of herbivore activity (tracks and scats) and burrowing activity by larger reptiles and mammals (burrows greater than a twenty cent coin in diameter). In addition, sand mounds were scored for Kowari habitat value using the methodology developed by Canty and Brandle (2008), which takes into account various parameters of mound condition, including shape and profile, damage by cattle and other herbivores, surfaces scalded by wind and water, hard crust and cryptogam cover, live vegetation and litter cover, height of vegetation and diversity of perennial and annual grass species. Additional opportunistic trap effort was carried out for Kowaris in areas that were identified as being suitable based on satellite imagery. Two traplines were set in Laundry Paddock, the first east of Rotten Swamp (100 traps over 10 km, opened for 2 nights, 15th and 16th May) and a second south of Gillan Gillan Waterhole (80 traps open for one night, 16th May). A line of 40 Elliot traps was also set along a sand dune in the same area following an observation of Ampurta (Dasycercus cristicauda) tracks. Figure 1. Map of central area of Clifton Hills Station, showing locations of PAN and WAL monitoring grids and the location of opportunistic trap lines set in Laundry Paddock. RESULTS AND DISCUSSION KOWARI MONITORING PAN Grid A total of 35 new individual Kowaris were captured on PAN Grid, including 17 males and 18 females over the four nights. Nine of these animals were subsequently recaptured. The majority of the animals caught were young individuals which had not bred before, indicating that they were the result of a reasonably recent breeding event (most likely Spring 2008). Two of the animals caught were very young (only recently independent of their mothers) and were caught in close proximity to each other on the western edge of the grid (row E). The age of these animals indicates some additional recent breeding, most likely associated with a flush of vegetation growth following a summer rainfall event. WAL Grid A total of 9 new individuals were captured on the WAL Grid, including 3 males and 6 females over the four nights and 7 of these animals were subsequently recaptured. Like the PAN Grid, these captures included several young individuals from a Spring 2008 breeding event. Densities of Kowaris at WAL Grid were 0.35 per km2 and at PAN Grid 1.35 per km2 (sample area of 26 km2 includes 500m buffer around grid). For WAL Grid, this density is consistent with trapping results over the previous four sessions, but well below the highest densities recorded in the 2001 and 2002 trapping sessions. Interestingly, the density of Kowaris on the PAN grid is the highest recorded to date. The reason for this discrepancy is not understood. However the vegetation response from rainfall presumably received in November and December 2008 (and more recently) seemed slightly greater at the Pandieburra Grid. It is also possible that the proximity to the flood event in Goyder’s Lagoon may have provided more available prey to the population near Pandieburra Bore. Large quantities of of moths, diving beetles and other insects were noticed around fluorescent globes at the campsite near Koonchera Dune and it is thought that some of the unseen benefits from the flood may be local increases in these insects within some distance from the floodwaters. This increased food source for Kowaris may also benefit other small mammals which Kowaris prey on, including Kultarrs and Hopping Mice. Table 1. Details comparison of capture rates and numbers of individuals at both grids over the last decade. The total number of captures is displayed, with the number excluding recaptures shown in brackets and the percentage trap success below. Site Trap Effort – Captures (individuals captured) trap nights % trap success August October May August April March June March May 1999 2000 2001 2001 2002 2003 2003 2006 2009 WAL 200 x 4 = 800 39* 32 (30) 50 (37) 54# (42) 67 (36) 16 (11) 4 (4) 6(6) 16(9)** GRID 3.3% 3.6% 6.3 % 5.7% 8.4% 2% 0.5% 0.75% 2% PAN 200 x 4 = 800 - - 30 (25) - 29 (19) 4 (3) 6(4) 13(7) 44(35) GRID 3.8 % 3.6% 1% 0.75% 1.6% 5.5% * no grids established. WAL site trap effort 1200 trap nights (400 traps x 3 nights set in long lines) # 50m x 50m sub-grid within WAL GRID established. WAL site trap effort 940 trap nights (100 x 1 night + 380 x 3 nights) ** trap effort in WAL grid slightly less: 720 trap nights (20 traps on dune not set) OTHER SMALL MAMMAL SPECIES As with previous trapping sessions, several other small mammal species were captured in Elliot traps and observed on the monitoring grids in spotlights or vehicle headlights. Comparable numbers of Kultarrs (Antechinomys laniger) and Fawn Hopping Mice (Notomys cervinus) were captured in the current trapping session (Table 2.). Similar numbers of Kultarrs were caught on the two grids (4 on WAL grid, 5 on PAN grid), however Fawn Hopping Mice were only captured on the PAN Grid during this session.