A review of wombat diet and nutrition

In this review we investigated the diet and nutrition of wombats and highlight areas for future research. The low energy requirements of wombats, conservative foraging behaviours and burrowing lifestyle allow them to subsist on low-quality food. Furthermore, their digestive anatomy and physiology is well adapted for digesting the resources available in their habitats. All species feed predominantly on native grasses; however, the nutritional requirements of juvenile and aged wombats are largely unknown. Changes to food availability and grass species in wombat habitats may alter their diet and nutritional intake. Also, despite evidence suggesting that wombats can satisfy their water requirements via the food they eat, the minimum threshold of water content at which wombats will cease feeding is unknown. Other areas for future research include investigating factors that affect digesta retention times (such as age or lactation), and the development of a method to determine age, because unlike most other mammals, wombat teeth grow continuously, hence teeth cannot be used as a reliable predictor of age in wombats.

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.

Genetic monitoring of southern hairy-nosed wombats over two decades reveals that individuals can live for at least 18 years in the same warrens

Survival and growth rates are important demographic parameters to understand for long-term management of populations. Eighteen years have elapsed since non-invasive genetic methods were used to identify southern hairy-nosed wombats (Lasiorhinus latifrons), and determine space use and relatedness at Brookfield Conservation Park, South Australia. Because the species is long-lived (>30 years) and genetic methods can identify all or most wombats that use an area, it is possible to determine whether population size or warren use have changed and if any individuals are still alive. To this end, in April 2017 we collected hair from wombats from the same warrens as the earlier study using sticky tape suspended across burrows. We subjected DNA from selected hairs to 10 microsatellite loci and a Y-linked sex marker, and identified 76 wombats. Five wombats were detected 16–18 years before, and four of them were found in warrens that they had used previously. The number of tapes hit, wombats detected, and warrens used were greater than in April 2001 and similar to September 2001. This study illustrates that non-invasive sampling methods can be used to track free-ranging individuals in continuous habitat across decades, despite rapidly evolving genetic technology that can strand older datasets.

Square salads: exploring the diet of the southern hairy-nosed wombat (Lasiorhinus latifrons) via DNA metabarcoding

Southern hairy-nosed wombats (Lasiorhinus latifrons) are large semi-fossorial marsupials that inhabit semiarid areas of southern South Australia and southeast Western Australia. Despite their size and prominence on the landscape, little is published about diet and foraging preferences. Further, it is unclear whether this wombat species’ diet overlaps with sympatric western grey kangaroos (Macropus fuliginosus), which are locally abundant across the southern hairy-nosed wombat’s distribution. Competition for food resources may be an added stressor in Murraylands populations where kangaroos are plentiful. Here, we identified diet items and dietary overlap of southern hairy-nosed wombats and western grey kangaroos. We accomplished this by opportunistically sampling fresh faecal pellets from both species at Brookfield Conservation Park in April 2017. We performed DNA metabarcoding via Illumina next generation sequencing of the faecal DNA using the plant ITS2 gene. We identified 10 genera in the wombat diet and 20 in the diet of kangaroos; diets of both species included native and introduced genera. Eight genera were shared between both marsupials. This work highlights the capabilities of non-invasive genetic sampling in concert with DNA metabarcoding to elucidate diet and dietary overlap between species.

A quick drink: the response of southern hairy-nosed wombats (Lasiorhinus latifrons) to rainfall

This paper describes opportunistic observations of the response of wombats to rainfall. Within a few minutes after heavy showers of rain wombats congregated to drink at an area of exposed calcrete (limestone) where water had accumulated. The wombats interacted socially much more than is typical for wombats. This event demonstrates a level of understanding of their environment and of the availability of a transient resource that has not been documented previously.

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%).

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

Simple Summary

While many people have great affection for southern hairy-nosed wombats, they are also considered by others to be an agricultural pest, because of the damage they can cause to farmland and agricultural infrastructure. Therefore, we need to have a good understanding of how many wombats there might be and how the population is changing, if we are to make properly informed decisions on how to best manage them. Unfortunately, because wombats are nocturnal and live underground, and because they use a number of different burrows throughout their home ranges, counting them can be difficult. We used motion-activated cameras to record how often wombats use each burrow in order to develop a reliable method of counting wombats that we can apply at the broad scale. We found that, on average, there are around 0.43 wombats for each active burrow. The use of video cameras to record this information provided a much simpler and less invasive means of researching wombat behaviour than methods such as trapping. However, video cameras do have limitations that need to be considered, and researchers need to fully understand their capabilities and limitations before employing them in the field.

Abstract

Broad-scale abundance estimates of the southern hairy-nosed wombat population use a proxy measure based on counting the number of active burrows, which is multiplied by an index of ‘wombats/active burrow’. However, the extant indices were calculated in the 1980s, prior to the use of calicivirus to control rabbits, and used invasive monitoring methods which may have affected the results. We hypothesise that the use of video might provide a logistically simple, non-invasive means of calculating updated indices. To this end, motion-activated, infra-red still and video cameras were placed at various distances outside active wombat burrows in the South Australian Murraylands and Eyre Peninsula regions. The captured imagery was inspected to determine how often the burrow was occupied by one or more wombats, and how effective the cameras were at detecting wombat activity. Video data was clearly superior to the still imagery, with more than twice as many burrow occupancies being positively identified (still: 43%). The indices of wombats/active burrow calculated based on video imagery were: Murraylands: 0.43, Eyre Peninsula: 0.42. 1948 false positive videos were recorded, of which 1674 (86%) occurred between noon and sunset.