An Attempt at Age Estimation of the Ryukyu Long-Furred Rat (Diplothrix legata) Using Tooth Wear Analysis: First Report on the Difference in Molar Wear Patterns between Rats in Okinawajima and Amami-Oshima Islands

Researchers found that molar wear patterns differ significantly between Ryukyu Long-Furred Rats (Diplothrix legata) on Okinawa Island and Amami-Oshima Island, complicating age estimation methods. By analyzing 106 skulls—87 from Okinawa and 19 from Amami—the study identified seven distinct stages of molar wear, with Stage I (minimal wear) only observed in Okinawa rats, suggesting these were recently weaned individuals under 50 mm in skull length. However, Amami rats showed inconsistent relationships between fur growth, skull size, and tooth wear, indicating that age estimation based on molar wear may not apply uniformly across islands. The findings highlight the need for island-specific approaches to studying this endangered species' lifespan and ecology.

Nakanishi, N., Tsubasaka, Y., Sawanaka, I., Kondo, K., Kobayashi, S., Izawa, M., & Hayashi, S. (2025). An Attempt at Age Estimation of the Ryukyu Long-Furred Rat (Diplothrix legata) Using Tooth Wear Analysis: First Report on the Difference in Molar Wear Patterns between Rats in Okinawajima and Amami-Oshima Islands. Mammal Study, 50(2), 211–218. https://doi.org/10.3106/ms2024-0074