The oral microbiome is implicated in a wide diversity of fundamental biological functions, with the oral cavity serving as a connection between the host and the external environment. Dental calculus, a mineralized form of dental plaque, preserves the diversity of biomolecules found in the oral cavity through time, serving as a rich source of historical microbiota. Despite its potential, dental calculus has rarely been explored outside of humans and non-human primates. Hence, it remains unclear how ubiquitous it is across mammals. Using natural history museum collections, we surveyed > 1600 specimens belonging to 142 species, representative of almost all mammalian orders, to investigate the taxonomic distribution of dental calculus, and to identify factors that most strongly contribute to its formation. We found dental calculus to be abundant across mammalian taxa, with 104 surveyed species showing calculus. High-fiber diets were most strongly associated with calculus abundance, whereas species with high protein and fat diets showed little to no calculus deposits. We found evidence of phylogenetic signal in calculus formation, pointing to the effects of oral/dental morphology. In addition, captivity strongly affected dental calculus formation in almost all dietary categories. Using this information, we made predictions about the likelihood of finding dental calculus in unsurveyed mammalian species, opening doors for its utilization for the study of oral microbiota, past and present. Our study found that dental calculus is well-preserved and readily available in natural history museum collections, making it an easily accessible source of oral microbiota from wild animals. We highlight the taxonomic diversity of species presenting dental calculus and provide information and suggestions for its use to researchers and curators alike.