Dental and skull anomalies in feral coypu, Myocastor coypus

Abstract

The study of dental and skull abnormalities of wild animals can provide useful information for comparative studies. Although studies of captive and laboratory rodents have been published, there are few reports on wild populations. We examined anomalous and pathological conditions in the skulls of feral coypus, Myocastor coypus, from Aichi Prefecture, Japan, and identified the types of abnormality. Of the 203 coypu skulls of various ages examined, 19 specimens (9.4%) had abnormalities. A total of 23 anomalies were divisible into three categories: dental diseases, dental injuries and skull injuries. Seven specimens (3.4%) had evidence of periodontal disease in the cheek teeth, and one specimen (0.5%) had caries. Seven specimens (3.4%) had broken upper or lower incisors. Four specimens (2.0%) had injured cranial bones and three (1.4%) had fractures near the zygomatic arch. A single specimen (0.5%) had a deformed rostrum. No statistically significant differences between the genders were found in any category ( χ 2 test: P < 0.05). The incidence of dental disease appeared to be related to the biological characteristics of this species, i.e., long lifespan, herbivorous diet and molar crown morphology. By contrast, dental and skull injuries appeared to be due to trauma caused when farmers attacked feral coypus.