Capercaillie and human disturbance

How susceptible is the capercaillie to human disturbances? This projects examines the behavioural and physiological consequences of human disturbance in this red-listed grouse.

Aims

Disturbance by human outdoor activities is discussed as a possible reason for the population decline of capercaillie (Tetrao urogallus) in Central Europe. However, few attempts have been made so far to measure the susceptibility of capercaillie to human disturbance. In this study, we investigated both habitat use as a behavioural response and fecal concentrations of corticosterone metabolites as a physiological response of capercaillie to human winter recreation activities. An indicator for disturbance causing physiological stress is the increase of the glucocorticoid corticosterone, a stress hormone that helps to cope with life-threatening situations. The aims of this study were (1) to select and validate an enzyme immunoassay for the quantification of corticosterone metabolites in capercaillie droppings and to test the influence of various storage conditions, (2) to evaluate stress hormone levels in capercaillie droppings according to temporal and spatial variation of winter tourism activities in the Swiss Alps, and (3) to investigate whether winter tourism changes the range use of radio-tagged capercaillies in the Black Forest, Germany.

Approach

In the lab an enzyme immunoassay was set up to measure corticosterone metabolites in capercaillie droppings. Field work was conducted in Germany and Switzerland. During three winters 2003-06, 13 capercaillies were radio-tracked. In the Southern Black Forest in Germany, 396 droppings of these and additional individuals were sampled before and after the start of the ski season. We tested whether the intensity of human winter recreation activities affected home range location and habitat use, and we identified the factors influencing the concentration of corticosterone metabolites in droppings.

Results

Metabolites of corticosterone in droppings of capercaillie were elevated in areas with high winter sport recreation intensity. This physiological response to disturbances could be measured in 68 areas of the Black forest, the Swiss Jura and the Swiss Alps. Prior to the ski season, capercaillie used the forests independently of the few touristic activities. During the ski season, capercaillie favoured areas with little disturbance within their home ranges, while areas with intense touristic activities were avoided except during bad weather when no tourists were present.

Flight distance in areas with intense touristic activities and in open forests was higher than in dense forests with few tourists. Capercaillie of all studied populations favoured beech and pine trees as sleeping trees and avoided the common spruce. We assumed that the possibility to detect predators influenced the choice of the sleeping tree more than climatic protection.

Our results underline that the capercaillie is highly sensitive to disturbances. The changes in habitat use, behavioural and physiological reactions might potentially affect the energy metabolism and fitness. Fitness costs during winter are especially high, because food intake is limited by the energy-poor pine needles and the short days.

Project management

This study was conducted as a PhD thesis by Dominik Thiel, who was supervised by Lukas Jenni and Susi Jenni-Eiermann.

Partners

The close and interdisciplinary collaboration of several research group resulted in synergies, which allowed to uncover facts highly relevant to the conservation of this endangered species.

Prof. Dr. Peter Berthold, Max-Planck-Institut für Ornithologie
Dr. Rudi Suchant, Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg FVA
Prof. Dr. Rupert Palme und Prof. Dr. Erich Möstl, University of Veterinary Medicine Vienna
EU Life Nature-Cooperation Project, Grouse and Tourism in NATURA 2000-areas
Dr. Emmanuel Ménoni, Office National de la Chasse et de la Faune sauvage ONCF, France

Financial support

Janggen-Pöhn-Stiftung
Lotteriefonds des Kantons Schwyz
Federal Office for the Environment FOEN
International Council for Game and Wildlife Conservation CIC