Hair cortisol is increasingly being used in animal welfare science as an indicator of negative/long-term stress in animals, assessed by concentration. Various studies have indicated that hair colour may affect the cortisol concentration, however, the evidence for this is mixed; whilst some studies do observe a difference in hair cortisol concentrations by hair colour (Bennett and Hayssen, 2010; Bowland et al., 2020; Moody et al., 2022), others do not (Rosen et al., 2016). This poses a clear issue and risks undermining the validity of studies using hair cortisol. As a result, it is essential that we understand factors that could influence hair cortisol levels that should be controlled or accounted for during future (and past) research. Furthermore, this phenomenon has not been thoroughly assessed in cats, with evidence to date predominantly being from cattle and dogs.

This project aims to assess variations in cortisol concentrations in cat hair based on the colour of the hair; the null hypothesis states that there is no significant difference in hair cortisol concentration between different colour hair. Hair from bi-colour cats was collected (black and white OR ginger and white), which provided paired samples for direct comparison. Primary information about each cat was also collected, such as age, sex, breed, neutering status etc. Once collected, hair samples were cleaned and ground, and the cortisol was extracted and quantified via ELISA. Cortisol concentrations were then directly compared across hair colours using a paired T-test. A significant difference was determined between cortisol concentrations in black/ginger hair compared to white hair throughout (p<0.001). To date, evidence is mixed as to whether hair colour does affect the accumulation of cortisol, and whether the colour has the same effect in every animal. Ultimately, it is essential that we understand factors that could influence differences in cortisol accumulation in animals. Testing this in cats will aid future research to improve methods of measuring stress and the relative welfare of cats.