Evaluation of the physiological stress response induced by winter sports in a black grouse (Tetrao tetrix) population from Lepontine Alps

In the Alps, human outdoor leisure activities are an increasing conservation issue having a strong impact on wildlife, mainly on endangered species, such as black grouse (Tetrao tetrix). Since freeriding sports are one factor affecting this species, it is important to quantify the likely pressure of recreational disturbance on their health status considering that induced stress can alter animal fitness. Using a non-invasive technique we examined the physiological stress response of a black grouse population from Central Alps induced by snow sports in relation to areas with different humandisturbance. During two winters (2011 and 2012) we sampled 58 fresh droppings from as many snow burrows to analyse concentrations of corticosterone metabolites (CM) by an enzyme immunoassay (EIA). In 2011, faecal CM levels in high human-disturbance areas were significantly higher (mean: 512±107 ng/g) than those in moderate (151±42 ng/g) and low disturbed (138±42 ng/g) ones, moreover higher CM concentrations were observed in areas closer to ski lifts. On the contrary, in 2012, no signifi cant differences in CM values were found between areas. Comparing results from sampling areas between study years, high-disturbed area CM levels were significantly higher in 2011 (m2011: 512 ng/g; m2012: 178 ng/g) while no significant differences were observed in moderate (m2011: 151 ng/g; m2012: 178 ng/g) and low (m2011: 138 ng/g; m2012: 211 ng/g) human-disturbed areas. Data show a great difference in high-disturbed areas CM levels between sampling years: in winter 2011 regular snowfalls have favoured the presence of skiers that elevate stress values and could represent a further threat to the fi tness of black grouse. In 2012 the lack of snow has drastically reduced winter sports with a consequent lower human disturbance, reflected to CM levels. Moreover in 2012 the increase of population baseline CM values in low disturbed areas suggest a more stressful condition as they have to acclimate to these unusual meteorological trends.