Coat color and other factors influencing hair cortisol concentration in domestic cats

Hair cortisol quantification can be used to understand long-term stress in cats and other animals. The technique is becoming increasingly common; however, there is uncertainty as to the factors that may affect or confound hair cortisol quantification, in particular, hair color. Although some studies show that hair of different colors has different abilities to store cortisol, others do not. We collected hair samples from 27 domestic cats with either black-and-white or ginger-and-white haircoat coloring. From each cat, 2 samples were taken, 1 of white hair and 1 of the other color (black or ginger). Samples underwent cortisol quantification by ELISA, and pairwise analysis was conducted. Hair cortisol was also compared against information provided by the cat owners regarding their cat (e.g., sex, age) and behavioral issues. Black hair contained significantly greater concentrations of cortisol than white hair ( p = 0.016). Although ginger hair tended to have higher mean cortisol concentrations than white hair, the difference was not statistically significant ( p = 0.613). A significant positive correlation was also found between hair cortisol and behavioral issues reported by owners ( p = 0.010). To our knowledge, the impact of the color of the hair on feline hair cortisol concentrations has not been reported previously.