Effects of climate on dental mesowear of extant koalas and two broadly distributed kangaroos throughout their geographic range

Abstract

Dental mesowear analysis can classify the diets of extant herbivores into general categories such as grazers, mixed-feeders, and browsers by using the gross wear patterns found on individual teeth. This wear presumably results from both abrasion (food-on-tooth wear) and attrition (tooth-on-tooth wear) of individual teeth. Mesowear analyses on extinct ungulates have helped generate hypotheses regarding the dietary ecology of mammals across space and time, and recent developments have expanded the use of dental mesowear analysis to herbivorous marsupial taxa including kangaroos, wombats, possums, koalas, and relatives. However, the diet of some of the most ubiquitous kangaroos (e.g., Macropus giganteus) along with numerous other species cannot be successfully classified by dental mesowear analysis. Further, it is not well understood whether climate variables (including precipitation, relative humidity, and temperature) are correlated with dental mesowear variables including various measures of shape and relief. Here, we examine the relationship between dental mesowear variables (including traditional methods scoring the sharpest cusp and a new potential assessment of multiple cusps) and climate variables in the grazers/mixed feeders Macropus giganteus and Macropus fuliginosus, and the obligate browser Phascolarctos cinereus. We find that dental mesowear of mandibular teeth is capable of differentiating the dietary habits of koalas and the kangaroo species. Furthermore, both Macropus giganteus and Phascolarctos cinereus exhibit mesowear correlated with mean minimum temperature, while Macropus fuliginosus dental mesowear is unaffected by temperature, despite significant differences in mean minimum and mean maximum temperature across their distribution (and in the specimens examined here). Contrary to expectations that individuals from drier regions would have blunter and lower relief teeth, dental mesowear is unrelated to proxies of relative aridity—including mean annual precipitation and relative humidity. Collectively, dental mesowear in these marsupials is related to feeding behavior with increased wear in cooler regions (in Macropus giganteus and Phascolarctos cinereus) potentially related to more or different food resources consumed.

Case series: Computed tomography (CT) demonstrates lacrimal canal involvement in koalas (Phascolarctos cinereus) with maxillary incisor dental disease

“…A variety of factors contribute to the development of dental disease in koalas 1–5 . Dietary requirements result in continuous grinding of molar teeth; this progressive wear and erosion of crowns with age predisposes aged koalas to periodontal disease.…”

“…A variety of factors contribute to the development of dental disease in koalas. [1][2][3][4][5] Dietary requirements result in continuous grinding of molar teeth; this progressive wear and erosion of crowns with age predisposes aged koalas to periodontal disease. Malocclusion also contributes to excessive wear of the occlusal surfaces and subsequent pulp exposure, allowing bacteria to ascend and cause periodontitis or endodontitis.…”