Landscape of stress: Tree mortality influences physiological stress and survival in a native mesocarnivore

Climate change and anthropogenic modifications to the landscape can have both positive and negative effects on an animal. Linking landscape change to physiological stress and fitness of an animal is a fundamental tenet to be examined in applied ecology. Cortisol is a glucocorticoid hormone that can be used to indicate an animal’s physiological stress response. In the Sierra Nevada Mountains of California, fishers (Pekania pennanti) are a threatened mesocarnivore that have been subjected to rapid landscape changes due to anthropogenic modifications and tree mortality related to a 4-year drought. We measured cortisol concentrations in the hair of 64 fishers (41 females, 23 males) captured and radio-collared in the Sierra National Forest, California. We addressed two main questions: (1) Is the physiological stress response of fishers influenced by anthropogenic factors, habitat type, canopy cover, and tree mortality due to drought in their home range? (2) Does the physiological stress response influence survival, reproduction, or body condition? We examined these factors within a fisher home range at 3 scales (30, 60, 95% isopleths). Using model selection, we found that tree mortality was the principle driver influencing stress levels among individual fishers with female and male fishers having increasing cortisol levels in home ranges with increasing tree mortality. Most importantly, we also found a link between physiological stress and demography where female fishers with low cortisol levels had the highest annual survival rate (0.94), whereas females with medium and high cortisol had lower annual survival rates, 0.78 and 0.81, respectively. We found no significant relationships between cortisol levels and body condition, male survival, or litter size. We concluded that tree mortality related to a 4-year drought has created a “landscape of stress” for this small, isolated fisher population

Landscape use by fishers (\u3ci\u3ePekania pennanti\u3c/i\u3e): core areas differ in habitat than the entire home range

Home ranges have long been studied in animal ecology. Core areas may be used at a greater proportion than the rest of the home range, implying the core contains dependable resources. The Pacific fisher (Pekania pennanti (Erxleben, 1777)) is a rare mesocarnivore occupying a small area in the Sierra Nevada Mountains, California, USA. Once statewide, fishers declined in the 1900s due to trapping, habitat fragmentation, and development. Recently, drought induced by climate change may be affecting this population. We examined space use of fishers in their core versus their home range for levels of anthropogenic modifications (housing density, road density, silvicultural treatments), habitat types, and tree mortality. We found core areas contained more late-successional forest and minimal human activity compared with their territory. Their core had higher levels of dense canopy and higher amounts of conifer cover, while minimizing the amount of buildings, developed habitat, and low canopy cover. Fishers may in effect be seeking refugia by minimizing their exposure to these elements in their core. Conserving landscape components used by fishers in their core areas will be important for the persistence of this isolated population. Les domaines vitaux sont étudiés depuis longtemps en écologie animale. Les aires principales pourraient être utilisées en plus grande proportion que le reste du domaine vital, ce qui sous-entend qu’elles renferment des ressources fiables. Le pékan (Pekania pennanti (Erxleben, 1777)) est un mésocarnivore rare qui occupe une petite région de la chaîne des Sierra Nevada, en Californie (États-Unis). Autrefois présents dans l’ensemble de l’État, les pékans ont connu un déclin au 20e siècle causé par le piégeage, la fragmentation de leurs habitats et l’aménagement du territoire. Des sécheresses récentes induites par les changements climatiques pourraient avoir une incidence sur cette population. Nous avons comparé l’utilisation de l’espace par les pékans dans leurs aires principales et dans leurs domaines vitaux pour différents degrés de modifications d’origine humaine (densité de logement, densité de routes, traitements sylvicoles), types d’habitats et taux de mortalité des arbres. Nous avons constaté que les aires principales des pékans renferment plus de forêts en fin de succession et très peu d’activités humaines comparativement à l’ensemble de leur territoire. Les aires principales présentent de plus grandes proportions de canopée dense et de plus grandes quantités de couvert de conifères, alors que la quantité de bâtiments, les habitats aménagés et le couvert forestier bas y sont très limités. Les pékans pourraient en fait chercher des refuges en minimisant leur exposition à ces éléments dans leur aire principale. La conservation d’éléments du paysage utilisés par les pékans dans leurs aires principales sera importante pour la persistance de cette population isolée

Landscape use by fishers: core areas differ in habitat than the entire home range

Home ranges have long been studied in animal ecology. Core areas may be used at a greater proportion than the rest of the home range, implying the core contains dependable resources. The Pacific fisher (Pekania pennanti Erxleben, 1777) is a rare mesocarnivore occupying a small area in the Sierra Nevada Mountains, California. Once statewide, fishers declined in the 1900s due to trapping, habitat fragmentation, and development. Recently, drought induced by climate change may be affecting this population. We examined space use of fishers in their core versus their home range for levels of anthropogenic modifications (housing density, road density, silvicultural treatments), habitat types, and tree mortality. We found core areas contained more late-successional forest and minimal human activity compared to their territory. Their core had higher levels of dense canopy and higher amounts of conifer cover, while minimizing the amount of buildings, developed habitat, and low canopy cover. Fishers may in effect be seeking refugia by minimizing their exposure to these elements in their core. Conserving landscape components fishers’ use in their core will be important for the persistence of this isolated population.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author