The population status of southern hairy-nosed wombats (Lasiorhinus latifrons). I. Distribution and abundance

There is disagreement within the community regarding whether the distribution and abundance of southern hairy-nosed wombats (Lasiorhinus latifrons) is increasing or decreasing. On one hand, farmers and graziers within areas where wombats can be found have consistently claimed that wombat numbers have increased in recent decades. Conversely, conservation groups, including the International Union for the Conservation of Nature (IUCN), claim that the wombat population is experiencing a species-wide decline, and recently upgraded its conservation status to ‘Near Threatened’. To resolve this disparity, we used a combination of field surveys and the analysis of satellite imagery to map the species-wide distribution and to estimate the overall population abundance of southern hairy-nosed wombats. We found that the wombat population has grown substantially since the last major surveys in the 1980s; however, the growth has not been uniform. While the population group in the Gawler Ranges has experienced marked population growth, there has been only relatively modest growth in the Murraylands. On the Yorke Peninsula, while the overall population numbers do not appear to have changed, some colonies have disappeared entirely. We also found a substantial population of wombats in Western Australia that had not been previously reported.

The behaviour and social development of young southern hairy-nosed wombats (Lasiorhinus latifrons)

Little is known about the ethology and behavioural ecology of young wombats. Observations of young southern hairy-nosed wombats (Lasiorhinus latifrons) that were still with their mothers revealed that they have an extensive ethogram that includes autonomous and social play, and precocial aggressive and defensive behaviours. The behaviour of one wombat was observed for 5–7 nights at monthly intervals from when it was first seen above ground with its mother (at an estimated age of 7–9 months). In the first 3 months it played often, and it remained within 25m of the natal burrow. Thereafter, the frequency of play declined, and it followed its mother further from the natal burrow. Five months after it was first seen it became independent of its mother when she moved to another warren. Nearly all the young wombat’s social encounters and interactions were with the group of wombats that occupied two warrens that included the natal burrow. At the time of the study, in 1975, only two of the nine juvenile and subadult wombats that were present at the warrens when the study started were still there 15 months later, which suggests that many young wombats disperse.

The population status of southern hairy-nosed wombats (Lasiorhinus latifrons). II. Landscape factors affecting distribution and abundance

The southern hairy-nosed wombat has a fragmented distribution across the arid and semiarid regions of southern South Australia and south-eastern Western Australia. Its distribution and abundance are highly patchy, with large clusters of warrens in some areas but few to no warrens in adjacent areas. In order to understand why this occurs, we mapped the species’ distribution and correlated the locations of over 8130 data points (5349 presence points and 2781 absence points) with environmental and landscape data. Overall, the wombat distribution is influenced by rainfall, with no wombats in areas where the mean annual rainfall is <154mm. Abundance is greatest in areas where rainfall is >227mm per annum. At the regional/local scale, warrens are found only in areas where the soil clay content is between 9 and 40%, and warren abundance is higher in open vegetation classes (saltbush/bluebush shrublands, grasslands) than in closed vegetation (mallee woodlands with shrubby understorey). Over-riding all of these environmental influences are anthropogenic land-use practices: although 38% of the wombats are located in protected areas and 51% are located on grazing land, they are virtually absent from croplands (~2%).