ANATOMY AND PHYSIOLOGY
2.1 Skull and dentition
The dental formula of the wombat is 1/1 0/0 1/1 4/4. Wombats have a highly ankylosed mandibular symphysis and their incisors and molars occlude simultaneously.
They are the only marsupials with aradicular hypsodont (elo- dont) dentition (the teeth are open-rooted and continuously growing) (Fiani 2015). Mastication is achieved via the maintenance of high compressive forces during modest horizontal excursions. The masseter and medial pterygoid muscles are greatly enlarged compared with other marsupials and in combination with the distinctive dentition facilitate the processing of a tough, abrasive diet. The bare-nosed wombat has a deeper masseteric fossa and a larger masseter muscle than the southern hairy-nosed wombat. In contrast, the temporalis muscles of the southern hairy-nosed wombat are bigger than those of the barenosed wombat and thought to generate a greater bite force (Sharp and Trusler 2015). Skull shape varies between individual wombats, likely due to different masticatory forces of the muscles on bone associated with different diets and feeding behaviours (Weisbecker et al. 2019).2.2 Thermoregulation
Wombat activity levels are temperature-dependent; behavioural thermoregulation is achieved through burrow use. Beyond 3 m of the entrance, ambient temperature and humidity in burrows are more stable than outside (Browne et al. 2021). Behaviour in the wild is noted to vary geographically (Borchard et al. 2012; Simpson et al. 2016). On mainland Australia healthy barenosed wombats consistently emerge from their burrows at dusk and have peaks of activity during the night, whereas in Tas. diurnal activity is commonly reported, especially when ambient temperatures are low.
In a study using implanted data loggers over a 9-mo period, core body temperature in zoo-housed southern hairy-nosed wombats proved to be moderately labile, with an 8°C range (30.9-38.8°C) (Descovich et al.
2017). Daily body temperatures sometimes fluctuated by more than 6°C. A nychthemeral body temperature pattern was evident, with a low during the day and a peak at night. Combined with the generally negative relationship between ambient and body temperatures, this suggests that thermoregulation is associated with activity phases in this species. Females were noted to have a higher mean body temperature than males.2.3 Digestive system
Like most other herbivorous mammals, harvesting energy from plant fibre relies on populations of symbiotic microbes residing in the wombat gastrointestinal tract. Preliminary studies suggest the gastrointestinal microbial communities become increasingly diverse from the stomach through to the colon, with the populations in the proximal colon, the putative site of primary plant fermentation, distinct from those in the distal colon (Eisenhofer et al. 2022).
The wombat colon produces 80-100 cube-shaped faecal droppings per night, which are frequently deposited around burrow entrances and on or next to prominent environmental points such as rocks, logs or trails. The intestinal features underscoring the formation of this unusual faecal shape have been investigated and it is hypothesised that cubes aggregate better in the environment than spheres (Yang et al. 2021; Magondu et al. 2023). Aggregations of cubic faeces within a wombat’s home range are presumed to be both a visual and olfactory source of communication.
3.