Dentition Anomalies and Cranial Abnormalities in Invasive Beavers (Castor canadensis) in Tierra Del Fuego, Argentina.

Simple Summary: The dentition analysis in vertebrates has been a pillar for the development of the classic and alternative theories on the evolution of species. The early dentition pattern consists of numerous, similar, and simple conical teeth, which are typically repeated in each half of both the maxilla and mandible. In mammals, however, dentition is regionally differentiated according to the dental arch, with dietary specialization being the main evolutionary pressure that defines the number, size, and shape of teeth. The developmental failure of a tooth normally present (hypodontia) and duplication of teeth (hyperdontia) is a deviation from the typical dental formula; their analysis allows for determining the prevalence of some dental conditions and their role in the health status of populations. After examining a sample size of 970 skulls of a total of 1121 beavers (Castor canadensis) that were removed in invaded areas of Tierra del Fuego, two dentition anomalies were recorded: hypodontia and hyperdontia (0.41% in both cases). Beavers also presented artifactual tooth loss (0.30%), acquired tooth loss (0.61%), fractured teeth (0.41%), and caries (0.31%). These conditions occurred in all age classes, showing a female bias, and represent a precedent of dentition anomalies and dentition and cranial conditions in an exotic invasive mammal. The study of dentition anomalies and pathologies in wildlife contributes, together with other indicators, to understanding the relevance of some factors on the health status of populations. This has not been properly evaluated in invasive mammals. To test the feasibility of eradication, the government of Tierra del Fuego performed the eradication of beavers (Castor canadensis) from 2016 to 2018: 1121 animals were removed and 970 examined. These beavers were examined to analyze the incidence of dentition anomalies and other dentition and cranial conditions. The beavers presented two dentition anomalies: hypodontia and hyperdontia (0.41% in both cases), and for the first time, a dentition anomaly in the upper quadrants was reported. Beavers also presented artifactual tooth loss (0.30%) and acquired tooth loss (0.61%) but with low incidence. The presence of fractured teeth (0.41%) and caries (0.31%) occurred in all age classes, also with low incidence. The third molar tooth was the most affected, showing a female bias. The 0.93% of skulls had a cranial abnormality represented as a buccal curvature. Malocclusion cases also were recorded (0.51%). The low prevalence of dentition anomalies, fractured teeth, caries, and cranial abnormalities would not compromise the lifespan of beavers. These results leave a precedent of dentition anomalies and dentition and cranial conditions in an invasive mammal. [ABSTRACT FROM AUTHOR]