Graham C. Medlin

The rodents of South Australia

Thirty species of rodents are recorded from South Australia. At the time of European settlement, the State probably supported at least 19 species of native rodents. Eight additional species have been recorded only in subfossil material. At least 11 species are now considered to be extinct and there have been significant declines in all the other species as a result of over 150 years of European influence. In addition, three species have been introduced to the State since European settlement. Over the last ten years, there has been a significant increase in our understanding of the distribution and ecology of what remains of the rodent fauna through a series of systematic, site-based biological surveys, a significant increase in research on subfossil and owl pellet remains, documentation of Aboriginal ecological knowledge and ecological and distributional studies on three species. This paper describes our current state of knowledge of the distribution, ecology and threats to the South Australian rodent fauna and makes suggestions for future research and conservation management.

Additional records of small mammals in northern South Australia

Analysis of prey remains found in predator scats is a valuable tool for assessing the distribution and status of small mammal populations. As part of a large-scale dingo research project in northern South Australia, the prey remains found in 1845 dingo scats were analysed. A range of species were identified as expected, though, of particular interest, additional records of Rattus villosissimus, Notomys fuscus and Pseudomys australis were obtained. Our R. villosissimus records confirm the contemporary range of this species in the north-eastern pastoral zone, while our N. fuscus records support other recent records of this species in the same area. Our P. australis record indicates that an isolated population of this species exists in the Strzelecki Desert, ∼400km east of the nearest known population. The status of these populations remains unknown, including the risk of dingo predation to them.

Natural Resource Management implications of the pre-European non-volant mammal fauna of the southern tip of Eyre Peninsula, South Australia

Sinkholes and coastal caves located in, around and between the Coffin Bay and Lincoln National Parks were surveyed for pre-European fossils, which were collected from or just below the sediment surface. Twenty-four pre-European fossil samples, including eight already in the collections of the South Australian Museum, were analysed and 25 native and five introduced species of non-volant mammal were identified. Native and introduced species were often found together, indicating that the sites have accumulated mammal remains in both pre- and post-European times. Only four of the non-volant native mammals recovered are known to be extant in the study area today: Lasiorhinus latifrons, Macropus fuliginosus, Cercartetus concinnus and Rattus fuscipes. In contrast, 20 native species recorded have been extirpated and one (Potorous platyops) is now extinct. C. concinnus was recorded from only one of the fossil assemblages but is known to be widespread in the study area today. This may indicate recent vegetation change related to European land management practices and have implications for natural resource management in the area.

The effects of drought on prey selection of the barn owl (Tyto alba) in the Strzelecki Regional Reserve, north-eastern South Australia

Changes in the diet of the barn owl (Tyto alba) were determined by analysing 619 egested pellets collected in eight samples over 12 months from a roost in the Strzelecki Regional Reserve, north-eastern South Australia. These data were used to examine the occurrence and change in frequency of small vertebrates in the region. In January 2003, at the end of a prolonged dry period, reptiles (predominantly geckos) dominated the diet of the barn owl, forming over 74% of Prey Units (PU%). This is the first Australian study to report reptiles as the primary prey of the barn owl. After substantial rain in February 2003, mammalian prey became much more common, and eventually accounted for almost 80 PU%. At least nine species of small mammal, at least four reptiles, nine birds and a frog were identified from the pellets. Mammalian prey included Leggadina forresti, Mus musculus, Notomys fuscus (endangered), Pseudomys desertor (not previously recorded in the reserve), P. hermannsburgensis, Planigale gilesi, Sminthopsis crassicaudata, S. macroura and Tadarida australis. This research showed that barn owls are capable of switching to alternative prey when mammals become rare, but that they return to preferred prey as soon as it becomes available.

Cryptic grey-bellied dunnart (Sminthopsis griseoventer) discovered in South Australia: genetic, morphological and subfossil analyses show the value of collecting voucher material

The assumption that almost all mammal species are known to science has led to a recent trend away from collecting voucher specimens/tissues during field studies. Here we present a case study of a recently discovered cryptic marsupial (Sminthopsis griseoventer) in South Australia (SA) and show how such collections can contribute to rigorous biodiversity and biogeographic assessments. Morphological and genetic (allozyme and mitochondrial control region (CR) sequence data) analyses, including ancient DNA analyses of type material, were applied to 188 voucher specimens and 94 non-vouchered tissues of Sminthopsis held at the SA Museum. These data were used to confirm the presence of S. griseoventer in SA, validate means of identifying it morphologically and describe recent and pre-European distributions. Pelage differences between S. griseoventer and S. dolichura enabled their identification, but external measurements overlapped considerably. Subfossil S. griseoventer were identified from seven deposits and confirmed that in the past the species was more widespread in SA. CR divergences (>1.8%) among Western Australian and SA S. griseoventer suggested its long-term presence in SA. Discrepancies between the mitochondrial and allozyme affinities of S. aitkeni and S. griseoventer, coupled with the lack of obvious morphological differences, indicate that a taxonomic reappraisal of these species is warranted. The study strongly demonstrates an ongoing need for the routine collection of mammal voucher material in biological and environmental impact surveys.

The Discovery and History of the Heath Mouse Pseudomys Shortridgei (Thomas, 1907) in South Australia

Abstract The Heath Mouse Pseudomys shortridgei was discovered in South Australia when a museum specimen collected from Kangaroo Island in 1967 was re-identified in 2000 and during trapping in the lower South East since 2001. These and subfossil records are summarized and compared with information from Western Australia and Victoria. Preliminary morphological comparisons of the single recent Kangaroo Island specimen and those from mainland South Australia and Victoria showed some differences in fur colour and body size. A total of 20 subfossil deposits containing P. shortridgei were documented in southern South Australia, spanning the Victorian to Western Australian borders. It and M. musculus were recorded together at only two sites, both surface deposits where material of different ages could have been mixed. At excavated sites, layers in which P. shortridgei was found were dated at <700 yBP in the lower South East of South Australia but the species was absent from layers dated <2000 yBP on the coast of the Nullarbor Plain. Pseudomys shortridgei was found in undated surface deposits collected from the Eyre and Yorke Peninsula along with other rodents that are both extinct and extant in the surrounding habitats. At these deposits, relative abundance compared with other rodents varied from 2.7 to 8.5%. Trapping of extant populations in the lower South East of South Australia has yielded trap successes of 2.0– 13.3%, a range that is broadly comparable with other states. Intensive surveys in the last 20 years have not trapped P. shortridgei on Kangaroo Island and its status there is unknown. Long-term climatic cycles (increasing aridity), and habitat clearance and fragmentation have probably resulted in the decline of P. shortridgei in South Australia.

Investigator Group Expedition 2006: Vertebrate Fauna

Abstract The vertebrate fauna of the Investigator Group includes 11 native (five now extinct) and four introduced mammals, 63 native and four introduced birds and 20 native reptiles. The determination of the total mammal fauna of Flinders Island was based on sub-fossil bone collections. The extinction of the Flinders Island form of the Tammar Wallaby between 1968 and 1974 is described. Australian Sea-lion and New Zealand Fur-seal breeding colonies and haul out sites on all the islands are documented. Sea-lion pup numbers on Ward Island greatly exceeded any previous reports.

Using the diet of the barn owl (Tyto alba) as an indicator of small vertebrate abundance in the Channel Country, south-western Queensland

The diet of the barn owl (Tyto alba) was determined by analysing pellets and bulk pellet debris found in the ruins of Baryulah Homestead, south-western Queensland. Nine species of mammal, at least eight bird, five reptile and three frog species were identified. The majority of prey consisted of small mammals and was dominated by Mus musculus, which accounted for almost 40 Prey Unit percent (PU%) of all prey. Rattus villosissimus was an important secondary prey species, which, due to its comparatively large mass, contributed 21.79 PU%. Other native mammals were present in low frequency only. Reptiles (primarily geckos) were more abundant than expected, collectively contributing >15 PU%, suggesting that they were an important component of the barn owl’s diet.

Fossils reveal late Holocene diversity and post-European decline of the terrestrial mammals of the Murray–Darling Depression

Abstract Context. Establishing appropriate faunal baselines is critical for understanding and abating biodiversity declines. However, baselines can be highly reliant on historical records that come from already disturbed ecosystems. This is exemplified in the Murray–Darling Depression bioregion of Australia, where European settlement (and accompanying marked land-management changes and the introduction of many species) triggered rapid declines and losses of native species, often before their documentation. Aims. We aim to establish the mammal fauna present when Europeans settled the Murray Mallee and Murray–Darling Depression bioregion and determine the extent of mammal loss since European settlement. Methods We describe a dated vertebrate assemblage from Light’s Roost in the lower Murray Mallee region of South Australia. We compare our data with those of modern fauna surveys and historical records to document the extent of change in the mammal fauna since European settlement. Key results. Radiocarbon ages showed that the assemblage was accumulating, at a minimum, within an interval from 1900 to 1300 years ago. Since this time, the Murray–Darling Depression has lost half of its flightless terrestrial mammals. Species lost include the mulgara (Dasycercus blythi/cristicauda), which places this taxon within only 40 km of Lake Alexandrina, the hitherto-disputed type locality for D. cristicauda. Fossils provided the principal evidence for nearly half of the Murray Mallee fauna and over three-quarters of the fauna are represented in the fossil record. Conclusions. Late Holocene assemblages provide important archives of species biogeography and diversity. Our revised faunal baseline indicated that the pre-European fauna of the Murray–Darling Depression was more diverse than hitherto understood and its reduction appears largely caused by the impacts of European settlement. Implications. Baselines for species distributions derived from historical records and modern faunal surveys are likely to be incomplete and warrant revision, particularly for smaller and more cryptic species. Deficiencies in regional records mask the extent of mammal declines caused by European colonisation and associated agricultural practices, and thus vulnerability to anthropogenic disturbance.