Wombats are short-legged, muscular quadrupedal marsupials native to Australia. Often called "badgers" by early settlers due to their size and habits, these herbivores have a diet primarily consisting of plant material. While they may resemble miniature bears, wombats lack the predatory skills, relying instead on the abundant grasslands and scrublands of Australia for sustenance. Let's delve into the specifics of what makes up a wombat's diet.
Primary Food Sources
The primary food for a wombat is grass. Australia is covered in grasslands and scrublands, providing a near-constant food source for these creatures. A wombat’s most common food is “snow grass,” which goes by another name, “tussock-grass,” and its scientific name, Poa sieberiana. Aside from snow grass, wombats are known to eat wallaby and kangaroo grass. Wallaby and kangaroo grass are also tussock grasses that grow in various regions across Australia. Wombats also consume sedges, other grasses, and the roots of various shrubs and trees. Their preference for certain foods, especially domestic crops, has sometimes caused them to have conflicts with farmers.
Foraging Behavior
Wombats are primarily foragers, generally nocturnal, emerging from dusk to dawn to search for food, though this can vary with the seasons. Many wombats will wander in a loop up to 1 mile long in search of food. When they find their food, they use their specialized teeth to slice the grasses or roots before eating.
Specialized Teeth
Wombat teeth are sharp and chisel-like, perfect for getting through fibrous and woody stems and grasses. Since the foods they eat are so tough, wombat teeth have evolved to never stop growing. All wombat teeth lack roots and are ever-growing, like the incisors of rodents. Like many other herbivorous mammals, they have a large diastema between their incisors and the cheek teeth, which are relatively simple.
Nutritional Adaptations
Wombats have an extraordinarily slow metabolism, taking around 8 to 14 days to complete digestion, which aids their survival in arid conditions. They also readily digest fibre, using hindgut fermentation and have powerful grinding jaws, resulting in maximum energy extraction from their diet. By optimising energy extraction from food, wombats are able to utilise low‐quality forage in a low production habitat. Southern Hairy-nosed Wombats extract most of the water they need from the food they eat. They have the driest poo of all mammals. Scientists believe its square shaped because their effective digestive system contracts and extracts water and nutrients from its food.
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Diet of Baby Wombats
Baby wombats, sometimes known as “joey wombats” or “joeys,” are about the size of a jellybean when they are born. Since wombats are marsupials, the babies will live in small pouches for protection while they nurse. Baby wombats drink the milk of their mothers for at least 12 months before being weaned off. Once weaned, they begin eating the same things that adult wombats do.
Dietary Adaptations in Response to Environmental Changes
Due to over grazing and drought in the Murray Lands, Southern Hairy-nosed Wombats have adapted to eat other foods, such as the corm of weeds such as Thread Iris to survive.
DNA Metabarcoding Studies
Traditional methods used to determine components of herbivorous diets include direct observation, scat microhistology, stable isotope analysis and stomach content protein electrophoresis, all methods vary in resolution and sampling bias, for example, due to differences in decomposition time and fragmentation of digested plant material, microhistology can overestimate the abundance and importance of species with a slower digestion time. Furthermore, identification to species level may be limited by the similarities between anatomical structures in related genera.
DNA metabarcoding is a more specific technique than traditional techniques, allowing more accurate identification to the species level, takes less time, and can identify cryptic species without the need for reference plant material. It is also not limited by the digestibility or physical attributes of the plant species. Consequently, several species that may not have been identified using microhistology will be detected using DNA metabarcoding. Faecal DNA metabarcoding is a non‐invasive, high resolution, cost and time‐effective tool frequently used to determine the diet of free‐ranging animals.
A recent study determined the diet of wombats through DNA metabarcoding across five study sites in New South Wales over a one‐year period. Metabarcoding was chosen as it is non‐invasive, less time consuming and more specific than traditional techniques. The list of 209 plant species identified as eaten by wombats in this study is much higher than previously reported, with grasses being the most common plant group identified in all samples. Most dietary items identified were introduced plant species. Seasonal differences in plants eaten occurred at four of the five study sites and may reflect dietary abundance and floristic composition at different times of year. The study found bare‐nosed wombats (Vombatus ursinus) eat mostly grasses, but dietary preferences are significant across season and are habitat specific.
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Regional Dietary Variations: A Detailed Look at Five Study Sites
To comprehensively understand the dietary habits of wombats, a study was conducted across five distinct sites in New South Wales (NSW), Australia. These sites, each with unique ecological characteristics, provide valuable insights into the adaptability of wombats to different environments and food sources.
1. Badger Ground
Located in Breakfast Creek, NSW, approximately 20 km from Rylstone, Badger Ground spans 330 ha of dry sclerophyll forest, grassy box woodland, and open grassland. Adjacent to a gully rainforest with natural springs, the property has transitioned from logging, livestock grazing (sheep and cattle), and a large-scale market garden to a protected area under a Conservation Agreement with NSW National Parks and Wildlife Service. This agreement includes managing feral and pest animals and noxious weeds. Supplementary feeding of the local wombat population occurs during low rainfall seasons with lucerne hay (Medicago sativa) and native grasses collected from roadside greenspace.
2. Coolagolite
Situated approximately 5 km northeast of Coolagolite, NSW, this privately-owned property lies within the Bega Valley Shire, an area characterized by wet and dry forests. The study site is primarily a cleared riparian zone surrounded by dry forest and dry rainforest, with Narira Creek running adjacent to the property. A Voluntary Conservation Agreement with NSW National Parks and Wildlife Service ensures active management of noxious weeds and feral animals, promoting increased native biodiversity. The area experiences a mean rainfall of 917 mm and a mean temperature range of 12-20°C.
3. Eagles Drift
Located approximately 30 km from Merriwa, NSW, Eagles Drift encompasses 577 ha of dry sclerophyll forest, box woodland, and open pasture. Previously used for sheep and cattle grazing, wheat (Triticum spp.) and barley (Hordeum vulgare) production, and bush rock collection, the property now hosts a small hobby cattle farm. A Conservation Agreement with the Nature Conservation Trust covers 270 ha, excluding cattle grazing to allow native vegetation regeneration. The area has an annual rainfall of 600 mm and a mean annual temperature range of 9-24°C.
4. Robertson
This site, a privately-owned property 8 km east of Robertson, NSW, is approximately 35 km from the coast and 5 km north of Budderoo National Park. Primarily used for sheep grazing, the landscape is mostly open grassland with small remnants of box woodland. Robertson, located in the southern highlands of NSW, is dominated by shale forest and woodland, with extensive cleared grassland for grazing. The area has a mean annual rainfall of 701 mm and a mean annual temperature range of 8-19°C.
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5. Wolgan Valley
Approximately 35 km north of Lithgow NSW, Wolgan Valley is adjacent to the Greater Blue Mountains World Heritage area. The study site is within the Emirates One&Only Wolgan Valley Eco Resort. Formerly a cattle station, the site has been managed as a luxury ecotourism resort for over a decade, with conservation programs including feral animal control, fauna surveys, and habitat regeneration. The landscape is dominated by open grassland surrounded by dry sclerophyll forest and remnant regrowth. The Wolgan River and Carne Creek run through the site, with minimal vegetation on the riverbanks, leading to erosion. The area has a mean annual rainfall of 758 mm and a mean temperature range from 5 to 25°C.
Factors Influencing Wombat Diet
Several factors can influence the diet of wombats, including seasonal changes, habitat, and the availability of food resources.
Seasonal Variations
Seasonal differences in plants eaten occurred at four of the five study sites and may reflect dietary abundance and floristic composition at different times of year.
Habitat Specificity
The diet of wombats exhibits variability across seasons and between different habitats, with potential shifts in the proportion of native and invasive species consumed based on factors such as resource availability, habitat preferences and interspecies interactions.
Wombats and Humans
Wombats are currently protected by the Australian government after years of hunting and killing drastically reduced their range and number. Now, with introduced animals and other predators, the wombat is further threatened. The main threats for wombats are animals like cattle and rabbits. Additionally, farming accidents involving wombats are all too common. Wombats are known to knock down fences in search of food on a farm, something that farmers don’t take all that kindly to.