Cortisol concentration in hair of the Baikal seal (<i>Pusa sibirica</i> Gmelin 1788, Carnivora, Phocidae): the effects of sex, age, and the dynamics of ice destruction

Measuring hair cortisol concentrations is a widespread method of hormonal research in natural populations. In particular, it has increasingly been used for assessing the chronic physiological stress over long time periods. This study showed for the first time the experience of using hair of Baikal seals to examine their hormonal status. We collected hair samples from live Baikal seals captured during summer expeditions to the Ushkany Islands, Lake Baikal in 2019 and 2021. Age differences in hair cortisol concentration were found: hair cortisol levels were higher among the young seals and declined with age. We suppose this may be related to different extents of nutritional stress, hunting success and social factors on summer rookeries. There was no sex effect on hair cortisol in young animals. We observed that hair cortisol concentrations were higher in young animals captured in 2019 compared to seals taken in 2021, with no differences in ice conditions between these years found.