Stress and bark peeling in red deer

Hertha Firnberg Position T 3 Stress and Bark Peeling in Red Deer Susanne HUBER 29.06.1999 Peeling damage by red deer (Cervus elaphus) is one of the major problems in wildlife management, often entailing high economic losses. Forest damage is assumed to be intensified as a consequence of stress, which to a large extent is caused by human disturbances or social stress. Frequent perturbations lead to a shift of activity and habitat use towards night-time and cover, resulting in digestion inefficiency which is supposed to be partly compensated by peeling. During winter, supplementary feeding has, therefore, been established, in order to keep peeling damage in check. Winter feeding, however, often implies social stress due to expulsion of subordinate individuals by dominants. The stress response is characterised by mobilisation of energy and increased cardiovascular tone along with suppression of digestion, growth, reproduction and immunity. These effects are produced by adrenal hormones, catecholamines and glucocorticoids. Hence, measuring blood concentrations of glucocor-ticoids serve to quantify the stress response. The collection of blood samples, however, can itself be a stressor which may obscure the results. As a consequence, non-invasive methods for the detennination of glucocorticoids have been developed. These assays utilise faecal samples that can be collected without any need to handle the animals, which is of particular importance in wildlife animals. Bark peeling may also be assessed by utilising faecal samples. Barks but no other plant parts contain suberin, an indigestible substance serving as the protective covering in higher plants. The measurement of faecal suberin content, therefore, represents a valuable tool for quantifying bark stripping. The study is aimed at validating non-invasive assays of analysing corticoid metabolites as a measure of stress and suberin content as a quantification of bark peeling in red deer. These methods will for the first time allow major causes of stress and the relationship between stress and peeling damage to be examined in a wildlife species, without any need to handle the animals. This type of analysis would not only broaden our understanding of causes and effects of stress in red deer, it would also be beneficial to the efficiency of wildlife management.