Academic literature on the topic 'Vombatidae'

This review provides an update on what is currently known about wombat reproductive biology and reports on attempts made to manipulate and/or enhance wombat reproduction as part of the development of artificial reproductive technology (ART) in this taxon. Over the last decade, the logistical difficulties associated with monitoring a nocturnal and semi-fossorial species have largely been overcome, enabling new features of wombat physiology and behaviour to be elucidated. Despite this progress, captive propagation rates are still poor and there are areas of wombat reproductive biology that still require attention, e.g. further characterisation of the oestrous cycle and oestrus. Numerous advances in the use of ART have also been recently developed in the Vombatidae but despite this research, practical methods of manipulating wombat reproduction for the purposes of obtaining research material or for artificial breeding are not yet available. Improvement of the propagation, genetic diversity and management of wombat populations requires a thorough understanding of Vombatidae reproduction. While semen collection and cryopreservation in wombats is fairly straightforward there is currently an inability to detect, induce or synchronise oestrus/ovulation and this is an impeding progress in the development of artificial insemination in this taxon.

There are few published studies on breeding and reproduction in hairy-nosed wombats and little information available on growth and development of pouch young. At a field site near Swan Reach in the Murraylands of South Australia morphometric measurements of 353 young southern hairy-nosed wombats and notes on their development were recorded. These data were combined with growth data collected from repeat measures of 10 mother-reared and 5 hand-reared joeys in order to establish information for aging young of this species and to plot developmental changes. Young weighed ~0.4 g at birth and had a head length (HL) of ~5.2 mm. Head length was the most accurate body parameter from which to assess age. Growth of pouch young was linear between birth and ~Day 310 with head length growing at ~0.4 mm HL per day. After Day 300 growth slowed, represented by a polynomial equation. Eyes were open at 5 months and pouch young started to develop fur at 5–6 months of age. Most young were permanently out of pouch at 9 months of age, and were weaned between 11 and 13 months, when they weighed 6–7 kg. Young remained in the burrow for 1–2 months following pouch exit before venturing above ground at night.

The two extant genera of wombats, the hairy-nosed wombat Lasiorhinus latifrons and common wombat Vombatus ursinus, are distinguishable by their skull morphology. Significant size differences were found for skull length, nasal length binasal breadth, bitemporal breadth, bizygomatic breadth, parietal bone thickness and mandible length. The important different gross morphological features are summarised to allow rapid identification of these two species. A number of new diagnostic differences are described which distinguish the species from dorsal, lateral and ventral views and on the basis of mandibles and dentition. Some of these differences, and those listed in the results, also distinguish the Pleistocene fossil wombats V. mitchelli (Owen, 1838) and L. krefftii (Owen, 1871) from each other, and strongly suggest their generic status.

Wombats (Vombatidae, Marsupialia) are fossorial marsupials that are most closely related to koalas amongst living marsupials. The cheek teeth of wombats are unique amongst Australian marsupials in being hypselodont (the condition where the teeth continue to grow throughout life and the formation of roots is suppressed). Hypselodonty is an adaptation to high degrees of tooth wear. The fossil record of vombatids is largely restricted to Pliocene to recent deposits and is largely represented by isolated teeth. Six genera are currently recognised from these deposits, all of which have hypselodont teeth. To date, a single isolated vombatid tooth has been described from pre-Pliocene deposits of South Australia and is the only example of a vombatid cheek tooth that possesses roots. Seventy specimens, representing five species of vombatid, have been recovered from Oligo-Miocene deposits in the Riversleigh World Heritage Site in northwestern Queensland and are described here. Among these are four new species and one new genus. A new species of Warendja from Riversleigh is described. It represents the oldest known hypselodont vombatid. This species is compared with additional specimens of the Pleistocene species of Warendja (W wakefieldi). Three species of Rhizophascolonus and a new monotypic genus are also described. Phylogenetic analysis of these taxa indicates that Rhizophascolonus may represent a sister taxon to the other vombatids. These specimens comprise almost all known examples of Oligo-Miocene vombatids. Most of the specimens are isolated teeth and are highly variable in size and morphology. Cusp detail is clearly preserved on many, allowing for omparison with the cusp morphology on juvenile cheek teeth of the common wombat (Vombatus ursinus). All of the taxa found in the deposits at Riversleigh share a number of characters such as marked differences in enamel thickness and height around the cheek teeth. It is argued here that these shared characters are indicative of high amounts of tooth wear and/or occlusal stresses acting on the trailing edge enamel. Combined with evidence of scratch-digging adaptations of the forelimbs it is suggestive of a rhizophagous niche for at least some of these early vombatids.

The northern hairy-nosed (NHN) wombat, Lasiorhinus krefftii, is critically endangered. It is restricted to a single population at Epping Forest National Park (EFNP) in semi-arid central Queensland. Apart from critically endangered status, the NHN wombat is unique among the larger grazing mammals because of its semi-fossorial lifestyle. This study investigated the feeding ecology of the NHN wombat, a key component in understanding the ecology of this species. Epping Forest National Park is a tropical savanna. The burrows of the NHN wombat are associated with alluvial sands of a ancient streambed and an open eucalypt woodland. The rainfall at EFNP is seasonal but irregular, and the study was conducted in four years of below average rainfall. The seasonal trends in rainfall result in variation in the quality and quantity of forage available to the NHN wombat. Fundamental to this thesis was measurement of temporal variability in the forage available to the NHN wombat. Forage quantity was monitored by the BOTANAL technique, allowing quantification of forage attributes including species composition, biomass and ground cover. In addition, primary productivity was monitored during the same period. Forage quality was measured by Near Infra-red Spectrometry (NIRS), calibrated to standard laboratory procedures. This technique allowed precise and reliable measurements of attributes of forage quality. These attributes included total nitrogen concentration, concentration of fibre (neutral detergent fibre, acid detergent fibre and acid-lignin), concentration of carbohydrates (water soluble carbohydrates), in vitro dry-matter digestibility (IVDMD) and organic matter content. The biomass and species composition of forage available to the NHN wombat was dominated by the introduced grass Cenchrus ciliaris (83.1 ± 6.4% of the total biomass). Of the native grasses, Enneapogon spp., Aristida spp. and Chrysopogon fallax dominated the biomass and species composition. In addition, the sedge Fimbristylis dichotoma occurred frequently, despite contributing little to the overall biomass. The diversity of forbs at EFNP was high, dominated by Waltheria indica, Salsola kalii and species of the Malvaceae. However, forbs represented only a minor component of the biomass and total species composition. Overall the biomass of the forage available to the NHN wombat was high, above 1000 kg.ha⁻¹ (dry matter) year round. Primary productivity was positively correlated with rainfall. The quality of forage species showed considerable temporal variation, with total nitrogen concentration in particular having a positive correlation with rainfall. Generally, the nutritional quality of the forage was poor, with seasonal variability in the concentration of nitrogen (range 0.3 to 2.5% of dry matter), concentration of fibre (range for neutral detergent fibre 54.9 to 86.8% of dry matter) and IVDMD (range 22.6 to 57.7% of dry matter). How the NHN wombat responded to such poor quality forage, both behaviourally and physiologically, was investigated. Estimating the species composition of the diet of the NHN wombat is a key issue in an understanding of its feeding ecology. However, techniques used to describe the diets of herbivores have often been questioned for their precision. Consequently three methods were used to estimate the composition of the diet of the NHN wombat: stable carbon isotope analysis, conventional histological analysis and long-chain alkane analysis. Stable carbon isotope analysis partitioned the diet into plants consumed that had a C₃ photosynthetic pathway (essentially forbs) or a C₄ photosynthetic pathway (tropical grasses). Using faecal samples and hair samples (representative of assimilated carbon incorporated into body tissue), it was determined that the diet of the NHN wombat consisted primarily of tropical grasses, but this approach could not describe the botanical composition of the diet. Analysis of epidermal residues and the concentration of long-chain alkanes in faeces were used to estimate the species composition of the diet. Conventional histological techniques compare the cell patterns of epidermal fragments in the faeces with a reference collection of epidermal patterns of plants available to the herbivore. Long-chain alkane analysis, however, takes advantage of the relatively indigestible wax component of the epidermis of plants consumed by the herbivore. One of the chemical components of the epidermal wax is long-chain alkanes (C₂₅ to C₃₆), each plant species with its own unique signature of alkanes. By comparing the patterns of long-chain alkanes in the faeces with a reference collection of plants available to the herbivore, through a least-squares optimisation procedure, an estimate of the composition of the diet could be generated. The diet of the NHN wombat was dominated by Aristida spp. (20.6 ± 6.0% of epidermal residues), Enneapogon spp. (17.2 ± 6.3% of epidermal residues) and C. ciliaris (14.5 ± 5.5% of epidermal residues), and to a lesser extent by W. indica (2.0 ± 2.0% of epidermal residues) and F. dichotoma (1.9 ± 1.6% of epidermal residues). Unidentifiable epidermal fragments were the largest component of the diet determined by the histological technique (40.4 ± 13.2% of epidermal residues). The NHN wombat exhibited little temporal variation in the plants it consumes, suggesting it is a generalist in its forage choice. However, both the histological technique and the long-chain alkane analysis have limitations. Despite these limitations, the estimation of the diet of the NHN wombat in this study is the best possible with current methods. Body composition of the NHN wombat was investigated by estimating levels of total body fat by Bioelectrical Impedance Analysis (BIA). The method of BIA was successfully calibrated on the southern hairy-nosed (SHN) wombat, Lasiorhinus latifrons, using stable isotopes of water and chemical analysis of the carcasses of SHN wombats. Multiple linear regression models using BIA plethysmograph measurements (resistance and impedance) and total body mass, were successful in predicting body fat (r² = 0.90, S.E. = 1.99) and total body water (r² = 0.90, S.E. = 1.64). Once calibrated, the BIA was applied to the NHN wombat. The NHN wombat maintained a relatively constant level of total body fat (7.6 ± 3.5% of total body mass) despite seasonal variability in the quality of available forage. However, there was some evidence to suggest that altered states of body composition (e.g. the storage of body fat) may be of considerable importance to females during lactation. The behaviour and activity of the NHN wombat were investigated by radio telemetry with data loggers incorporated into the collar packages. The three- channel data logger measured activity, intensity of light and temperature, with a recording schedule of one record from the three channels every 5 minutes and a data storage capacity of 1 Mb. The ranging behaviour of the NHN wombat was conservative, with core home-ranges averaging only 6.8 ± 3.8 ha (70% harmonic mean activity contour). Likewise, the activity of the NHN wombat was also conservative. The mean number of bouts of activity in a twenty-four hour period was just 25.2 ± 11.1 with each bout lasting on average 7.6 ± 2.2 minutes. Bouts of activity occur both above-ground and within the burrow, although the significance of activities within the burrow is unknown. When above-ground, the NHN wombat maintained low levels of activity, rarely undertaking behaviour that resulted in high measurements of activity. Above-ground activity was positively correlated with rainfall, and hence the quality and quantity of the forage. When rainfall was high, activity was low. However, the ambient temperature may also impose important limitations on the behaviour and activity of the NHN wombat. The habitat of the NHN wombat was shared by the eastern grey kangaroo, Macropus giganteus. The female adult body size of the eastern grey kangaroo is equivalent to the female adult body size of the NHN wombat allowing a comparison of aspects of their feeding ecology. Both herbivores have a preference for grasses with the species composition of their diets overlapping by more than 90%. Unlike the NHN wombat, the eastern grey kangaroo is not reliant on burrows. Following rainfall, the eastern grey kangaroo population declines in response to more favourable forage conditions beyond the boundaries of EFNP. They then return to EFNP as the quality and quantity of forage on surrounding pastoral properties decline. Although the density of eastern grey kangaroos is generally low on EFNP (seasonal range of 0.4 ± 0.6 to 16.9 ± 12.3 animals.km⁻²), the similarities in forage and habitat preference indicate that there is potential for competition of food resources. In summary, the lifestyle of the NHN wombat is one of extreme energy conservation, through its relationship with burrows, conservative behaviour and high digestive efficiency. The NHN is able to cope with the seasonally fluctuating savanna of northern Australia. The drought conditions encountered during this study resulted in a forage resource that was generally poor in quality. Despite possible nutrition restrictions, the NHN wombat exhibited little variation in its body composition or body condition throughout the study period. Therefore, the NHN wombat should be regarded as an extraordinary herbivore, well-suited to its semi-arid habitat.

In 2016 the conservation status of the southern hairy-nosed wombat was upgraded from ‘Least Concern’, to ‘Near Threatened’, based on an assessed population decline of up to 30% over the previous 25 years. Conversely, landholders in regions where wombats are present claim that the population has increased over recent decades. To resolve this discrepancy, we conducted a species-wide survey to determine overall wombat numbers and to establish any population trends. To do so, we had to develop reliable means of mapping the wombat distribution and estimating their abundance. We also conducted a literature review to estimate the likely distribution at the time of European settlement. We then used the findings from our survey to determine the factors which influence wombat distribution and abundance at different spatial scales. At the time of European settlement the wombat distribution was split into two main groups separated by Spencer Gulf. The western population extended to Balladonia in Western Australia, while the eastern group covered Yorke Peninsula and the mid-north, Murraylands, and extended along the northern bank of the Murray River to Euston in New South Wales. The population experienced a dramatic decline in the late nineteenth / early twentieth centuries because of human persecution and competition from rabbits. Using field surveys and the analysis of satellite imagery, we found that the wombat population has expanded in geographic range and overall numbers since the 1980s, although the rate of growth has not been uniform across the regions. Remote regions such as the Gawler Ranges and Nullarbor Plain have experienced the highest growth rates, while growth in the Murraylands has been moderate. We estimate the species-wide population at ~ 1.3 million. The population trend is difficult to establish, as earlier surveys did not include some areas in their assessments, including a population group in Western Australia that we surveyed for the first time. The index of 0.43 wombats / active warren, which we calculated by collecting video data on burrow occupancy rates, is similar to the indices that were calculated for the Murraylands in the 1980s / 90s. The environmental factors which shape the wombat distribution are rainfall, rainfall variability, soil texture and vegetation. Wombats are absent from areas with a mean annual rainfall of < 154 mm, with abundance declining when rainfall is < 227 mm. Wombats are unable to construct warrens in areas where the soil clay content is outside the range of 10 - 40% – with a preferred range of 16 – 28%. Wombats also show a preference for open vegetation types, with a lower occupancy rate in closed vegetation types. While the overall distribution has fragmented and declined, abundance is probably higher in some areas due to the clearance of mallee woodlands. The over-riding influence on whether wombats are present is land-use. While 38% of the wombat distribution is in protected areas and 50% on grazing land, wombats are virtually absent from croplands. This explains most of the fragmentary nature of the wombat distribution, and is the main cause of human / wombat conflict.
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2019