How the Distribution of the Common Wombat has Changed in Australia

How the Distribution of the Bare‐Nosed or Common Wombat (Vombatus Ursinus) has Changed in Australia.
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Abstract
A declining population of the bare-nosed wombats, also known as the common wombats, signals failures in understanding the habitat and distribution of the species. The aim of this paper is to review information about the bare-nosed wombats, especially the population distribution, habitats, and the potential factors that result in the decline of their population. This information will be critical in the conservation efforts of the species and help protect the common wombat from extinction.
Introduction
Wombats are large marsupial herbivores commonly known for their burrowing, a trait that makes them referred to as ecosystem engineers, according to ecologists (Thorley & Old, 2020). The burrowing impacts soil turnover rates, facilitate the recycling of nutrients and water filtration and creates many habitats for different species. However, this activity has been known to cause conflict with people and other animals such as horses and cows, and permits can be obtained to reduce their numbers when they conflict with farmers (Old, Lin, & Franklin, 2019). There are three wombat species across Australia, the bare-nosed, also known as the common wombat (Vombatus Ursinus), and the other two species of the hairy-nosed wombats, the northern hairy-nosed wombat (Lasiorhinus krefftii) and the southern hairy-nosed wombat (Lasiorhinus latifrons). Bare-nosed wombats were widespread in the past, but after the European settlement, their population has declined. While population numbers of bare-nosed wombats have in part contributed by the loss and contraction of habitats, these species are threatened by the introduction of species, roadkill, diseases, and both legal and illegal human activities (Thorley & Old, 2019). The aim of this paper is to review the available data on the habitat and distribution of Vombatus Ursinus and inform on the future management of the wombats.
Habitat and Distribution of Common Wombats
Common wombats live in temperate forest areas of Southeastern Australia and often avoid rainforests. In Northern New South Wales and southern Queensland, the species inhabits sclerophyll forests above 600 meters, while in Tasmania and South Australia, it lives in lower altitudes such as the coastal scrub, woodland, and heathland in open vegetation. In these habitats, wombats make burrows on slopes above gullies and creeks and often feed on grass clearings. About 200 years ago, during the European settlement, the distribution of the Common wombats was widespread in many places in Australia except the Northwestern corner of the Victoria state. The population of the species has since declined in New South Wales and Southeastern Queensland, as well as the southeast of South Australia, Tasmania, and the Bass Strait Islands (Australian Museum, 2021). Presently, the Common wombats have a fragmented and discontinuous distribution and have almost disappeared from the western areas of Victoria. Besides, bare-nosed wombats have completely disappeared from many regions of the New south wales that they ranged formerly. The Australian Museum (2021) reports that the species has declined in numbers in South Australia and only habits the Flinders Islands of the Bass Strait Islands, as shown in Fig 1 below.
Fig 1. Map of Australia showing the distribution of Common wombats (Australian Museum, 2021).
Following considerable human interference, bare-nosed wombats are now becoming extinct across the Bass Strait islands such as the Cape Barren, Clarke, Deal, and Flinders islands. In 2008, the species was listed as vulnerable through the Environment Protection and Biodiversity Conservation Act 1999 (Martin et al., 2019). Besides, Martin et al. (2019) have studied the effects of isolation, marine transgression, and translocation on the genetic divergence and speciation of the Common wombats. These factors largely influence gene divergence, genetic differentiation, and the population structure of the bare-nosed wombats. In examining the three allopatric subspecies of the Common wombats, the southeastern mainland’s V. u. hirsutus, the Bass Strait islands’ V. u. Ursinus and Tasmanian’s V.u. tasmaniensis, Martin et al. (2019) used previously collected tissue samples from bare-nosed wombats for the subspecies in the Australian mainland Bass Strait Island, Maria, and Tasmania Island for the study. The researchers found that isolation and translocation have an impact on the level of biodiversity among the bare-nosed wombats and highlighted that divergence and diversity affect the population size of the species when comparing both the island and mainland species.
Island and Mainland Distribution
Populations in island areas are phenotypically distinct from those in the mainland or elsewhere, and they are an important biogeographical factor that contributes to the global biodiversity of species through speciation and genetic divergence (Martin et al., 2019). Islands are known to be a reservoir for biodiversity, and populations in these areas are isolated from threats such as pests such as the Sarcoptes scabiei, a mite that causes serious symptoms of sarcoptic mange infection, leading to the deaths of the common wombats (Simpson, Johnson, & Carver, 2016). Mange in wombats affects not only their health but also their abundance and distribution. In southeastern Australia, the historical rise in sea levels after the last glacial maximum played a key role in shaping its biogeography. It is this event that separated Tasmania and other islands from the Australian continent during the Bass Strait flooding that protected some species from extinction. While the bare-nosed wombats are known as “common” and listed as the least concern under the IUCN Red List, the species has experienced retractions since the European settlement (Martin et al., 2019). For instance, the subspecies V.u. hirsutus is fragmented, and its population has been more than halved. A similar trend has been observed in V.u. ursinus that may not presently be found on Flinders Island after becoming extinct on Cape Barren, Clake, Deal, and King islands. However, the Tasmanian subspecies has always existed throughout Tasmania and has seemed a stable population.
Prehistoric Forces
Many prehistoric forces, such as the climatic changes of the Pleistocene, still remain clear in many species populations (Alpers et al., 2016). Besides, continental shelf islands experienced episodes of connection to larger landmasses through land bridges at the time of the glacial period when the sea levels were relatively low and, more recently, in the Pleistocene. Due to the differetial frequency, duration, and timing of the connections, as well as the nature of the intervening habitats, there have been gene flows between lineages that occupy today’s isolated regions. This aspect has led to concerns o...