Differences in hair coat condition between female and male mice occur through testicular-derived factors and are affected by the presence of another mouse.

An animal's coat protects its body from ultraviolet rays, physical and chemical damage, and temperature changes. It also plays an important role in showing individual information like a pattern for the outside world. In addition, changes in the condition of an animal's coat may occur due to health or psychological changes and are important indicators from the perspective of health management and the welfare of captive animals. Also, the quantity and texture of human hair play a role in the impression it gives to others; however, few reports have objectively quantified the appearance and detailed analysis of hair condition relative to the time of appearance. In this study, we quantified changes in hair coat condition and examined the underlying causes. The results indicated that changes in hair coat condition in male mice were significantly greater compared with that in female mice and were affected by testicular-derived factors and the presence or absence of cohabiting individuals. We also found that the condition of the coat is related to the length of the lift-edges cuticle region (LCR), which indicates that the cuticle condition affects the overall impression of the coat. This is the first report to show that changes in hair coat condition within sexual difference are related to the length of the LCR, suggesting that gender is a direct factor in the hair coat condition. Cohabitation, or the presence and relationship between one another, is an indirect factor.