Seasonal diet of omnivorous canid raccoon dog clarified from microscopic tooth scratches

A research team consisting of Associate Professor Mugino Kubo and Visiting Collaborative Researcher Ayako Kohno of the Graduate School of Frontier Sciences at the University of Tokyo, along with Graduate Student Takahiro Takahashi and Professor Yamato Tsuji of Ishinomaki Senshu University, has clarified that seasonal dietary changes can be read by analyzing the microscopic scratches (microwear) on raccoon dog teeth. This was discovered by examining the teeth of raccoon dogs that lost their lives to roadkill (death by collision with motor vehicles) in Ishinomaki City, Miyagi Prefecture. The findings also corresponded with the results of fecal analysis. This achievement is expected to be useful for restoring the paleoecology of fossil species. The results were published in Palaeogeography, Palaeoclimatology, Palaeoecology on May 22.

The raccoon dog is an omnivorous canid naturally distributed across East Asia, and its diet changes depending on the season and region. Microscopic microwear is left on the tooth surfaces when animals chew food, and these scratches reflect the hardness and properties of the food. This characteristic is used to reconstruct the diet of not only extant animals but also extinct animals.

On the other hand, because omnivorous canids utilize different foods depending on the season, it was not well understood what kind of dietary information microwear records.

Therefore, this time, the research group examined the teeth of roadkill raccoon dogs collected from September 2020 to October 2025 in Ishinomaki City, Miyagi Prefecture. The surfaces of the mandibular first molars and second molars were measured using a confocal laser microscope. Furthermore, they compared the results with analyses feces collected from the same region to investigate the relationship between tooth microwear and seasonal food.

As a result, a seasonal trend was seen in the tooth microwear. It was confirmed that the scratches tend to be relatively shallow from summer to early autumn, when raccoon dogs eat many insects, but become deeper from autumn to winter, when the utilization of fruits/seeds and vertebrates increases. It was found that the hardness of the food and the parts utilized are reflected in microwear.

In addition, scratches on the teeth of adults tended to be deeper than those of juveniles, which may be influenced by differences in bite force and foraging behavior associated with growth. There was no difference based on sex.

This will serve as a clue to clarify the diets of the extinct Japanese wolf and dogs excavated from archaeological sites, and to reconstruct the role of medium-sized omnivorous carnivores as seed dispersers in past ecosystems.

Kubo said, "This study started from the roadkill of wild animals, which is becoming a problem even in suburban areas. Raccoon dogs that lost their lives to roadkill became skeletal specimens through the dedication of students at Ishinomaki Senshu University, and the seasonal changes in their food became clear from the microscopic scratches on their teeth. Even with common animals, there are things that can be clarified for the first time only when many specimens are gathered, making this a study that conveys the significance of steady specimen collection. In the future, I would like to examine raccoon dogs in other regions as well."

Journal Information
Publication: Palaeogeography, Palaeoclimatology, Palaeoecology
Title: Seasonal dietary flexibility in the omnivorous raccoon dog (Nyctereutes procyonoides, Canidae) revealed by dental microwear texture analysis: Implications for paleoecology of canids
DOI: 10.1016/j.palaeo.2026.113884