Energetic balance is central to the survival and persistence of free-ranging animals. Quantifying expenditures and identifying factors that drive energetics informs our understanding of species’ ecology and their responses to shifting environmental conditions. Approaches used to estimate energetic expenditures of free-ranging species, such as doubly-labelled water (DLW), are precise but difficult to implement. Global positioning system (GPS) collars and accelerometers have emerged as alternatives for estimating expenditures, but these techniques have few applications in terrestrial species and no applications in small-bodied (<5kg) terrestrial animals. Here, we estimated movement characteristics and field metabolic rates (FMR) of Pacific martens (Martes caurina), a small-bodied carnivore with relatively high energetic costs, in a heterogeneous landscape to explore the role of movement and landscape characteristics on energetics. We concurrently used DLW and GPS collars to investigate the relationship between movement characteristics and FMR. Movement velocity explained the greatest amount of variation in mass-specific FMR and we used this relationship to predict expenditures of previously collared martens. We found that predicted mass-specific FMR was highest among males and increased in open patches primarily as a result of increased velocity and more erratic movements. Additionally, martens moving through deep snow also exhibited increased FMR. Our work shows movement metrics can effectively explain variation in FMR and identify landscape features, like forest structure and snow depth, that influence movements with cascading effects on energetics for free-ranging mammals in rapidly changing systems.

MartenData_Summaries_191121

This spreadsheet includes summary data regarding the energetic expenditures, landscape characteristics of use areas, and physical characteristics of martens monitored for this research.