A Comparison between Video and Still Imagery as a Methodology to Determine Southern Hairy-Nosed Wombat (Lasiorhinus latifrons) Burrow Occupancy Rates

Demographic trends and reproductive patterns in the northern hairy-nosed wombat (Lasiorhinus krefftii) at Epping Forest National Park (Scientific), central Queensland

The critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii) currently exists at only two locations in Queensland. Management, research and monitoring of the species at the main Epping Forest National Park (Scientific) population has occurred over the last four decades using a variety of tools, with the most complete dataset being provided by burrow activity monitoring over that period. Following a series of trap-based surveys in the 1980s and 1990s, wombat monitoring has employed DNA profiling of hairs collected remotely on sticky tape set at burrow entrances (since 2000), and passive infrared (PIR) cameras (since 2011). These techniques have produced a wealth of new information on the species. Using this new information, we aim to: (1) summarise the available demographic data and present new estimates using novel techniques for L. krefftii at Epping Forest NP; and (2) characterise reproductive patterns and their relationship with environmental factors for L. krefftii at Epping Forest NP. We find an ongoing increase in the population size at Epping Forest National Park, supported by healthy levels of reproduction despite periods of poor environmental conditions, notwithstanding the finding that cumulative monthly rainfall six months prior to sampling influenced birth rates. This trend suggests that the population will likely reach carrying capacity in the near future. It is timely to harvest the population to provide founders to a new site to establish an additional population, which will also reduce the risk of extinction and help secure the future of the species.

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.

Mapping out bare-nosed wombat (Vombatus ursinus) burrows with the use of a drone

Background

Wombats are large, nocturnal herbivores that build burrows in a variety of habitats, including grassland communities, and can come into conflict with people. Counting the number of active burrows provides information on the local distribution and abundance of wombats and could prove to be an important management tool to monitor population numbers over time. We compared traditional ground surveys and a new method employing drones, to determine if drones could be used to effectively identify and monitor bare-nosed wombat burrows.

Results

We surveyed burrows using both methods in eight 5-ha transects in grassland, that was interspersed with patches of tussock grassland. Ground surveys were conducted by systematically walking transects and searching for burrows. Drone surveys involved programming flights over transects to capture multiple images, from which an orthomosaic image of each transect was produced. These were subsequently viewed using ArcMap to detect burrows. A total of 204 individual burrows were recorded by drone and/or ground survey methods. In grassland, the methods were equally effective in terms of the numbers of burrows detected in transects. In the smaller areas of tussock grassland, ground surveys detected significantly more burrows, because burrow openings were obscured in orthomosaic images by overhanging grasses. There was agreement between the methods as to whether burrows were potentially active or inactive for most burrows in both vegetation communities. However, image interpretation tended to classify grassland burrows as potentially active. Overall time taken to conduct surveys was similar for both methods, but ground surveys utilised three observers and more time in the field.

Conclusions

Drones provide an effective means to survey bare-nosed wombat burrows that are visible from the air, particularly in areas not accessible to observers and vehicles. Furthermore, drones provide alternative options for monitoring burrows at the landscape level, and for monitoring wombat populations based on observable changes in burrow appearance over time.