Environmental and Intrinsic Correlates of Stress in Free-Ranging Wolves

PLoS One. 2015 Sep 23;10(9):e0137378. doi: 10.1371/journal.pone.0137378. eCollection 2015.

Abstract

Background: When confronted with a stressor, animals react with several physiological and behavioral responses. Although sustained or repeated stress can result in severe deleterious physiological effects, the causes of stress in free-ranging animals are yet poorly documented. In our study, we aimed at identifying the main factors affecting stress levels in free-ranging wolves (Canis lupus).

Methodology/principal findings: We used fecal cortisol metabolites (FCM) as an index of stress, after validating the method for its application in wolves. We analyzed a total of 450 fecal samples from eleven wolf packs belonging to three protected populations, in Italy (Abruzzo), France (Mercantour), and the United States (Yellowstone). We collected samples during two consecutive winters in each study area. We found no relationship between FCM concentrations and age, sex or social status of individuals. At the group level, our results suggest that breeding pair permanency and the loss of pack members through processes different from dispersal may importantly impact stress levels in wolves. We measured higher FCM levels in comparatively small packs living in sympatry with a population of free-ranging dogs. Lastly, our results indicate that FCM concentrations are associated with endoparasitic infections of individuals.

Conclusions/significance: In social mammals sharing strong bonds among group members, the death of one or several members of the group most likely induces important stress in the remainder of the social unit. The potential impact of social and territorial stability on stress levels should be further investigated in free-ranging populations, especially in highly social and in territorial species. As persistent or repeated stressors may facilitate or induce pathologies and physiological alterations that can affect survival and fitness, we advocate considering the potential impact of anthropogenic causes of stress in management and conservation programs regarding wolves and other wildlife.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Conservation of Natural Resources
  • Ecosystem
  • Feces / parasitology
  • Female
  • France
  • Helminthiasis, Animal / epidemiology
  • Helminthiasis, Animal / metabolism*
  • Hydrocortisone / metabolism
  • Italy
  • Male
  • Seasons
  • Stress, Physiological
  • Stress, Psychological / metabolism*
  • United States
  • Wolves / metabolism*
  • Wolves / parasitology

Substances

  • Hydrocortisone

Grants and funding

Funding was provided by the Institute of Biology of the University of Neuchâtel, Switzerland, the Fondation Gérard Pierre, the Fondation Pierre Mercier pour la Science (to R. Bshary) and the Fond Wüthrich et Mathey-Dupraz. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.