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Body mass is associated with hibernation length, body temperature, and heart rate in free-ranging brown bears
Alina L. Evans Inland Norway University of Applied Sciences
Jon M. Arnemo Inland Norway University of Applied Sciences
Jon E. Swenson Norwegian University of Life Sciences
Andrea Friebe Norwegian Institute for Nature Research
Ole Frobert Örebro University
Timothy G. Laske University of Minnesota
Stephane Blanc Hubert Curien Multidisciplinary Institute
University of Veterinary Medicine Vienna / Northern Michigan University
Alexandra Thiel Inland Norway University of Applied Sciences
Boris Fuchs Inland Norway University of Applied Sciences
Navinder J. Singh Swedish University of Agricultural Sciences
BMC
Despite centuries of research, debate remains on the scaling of metabolic rate to mass especially for intraspecific cases. The high variation of body mass within brown bears presents a unique opportunity to study the intraspecific effects of body mass on physiological variables. The amplitude of metabolic rate reduction in hibernators is dependent on body mass of the species. Small hibernators have high metabolic rates when euthermic but experience a drastic decrease in body temperature during torpor, which is necessary to reach a very low metabolic rate. Conversely, large hibernators, such as the brown bear (Ursus arctos), show a moderate decrease in temperature during hibernation, thought to be related to the bear's large size. We studied body mass, abdominal body temperature, heart rate, and accelerometer-derived activity from 63 free-ranging brown bears (1-15 years old, 15-233 kg). We tested for relationships between body mass and body temperature, heart rate, and hibernation duration.The smallest individuals maintained lower body temperatures during hibernation, hibernated longer, and ended hibernation later than large bears. Unlike body temperature, winter heart rates were not associated with body mass. In summer, the opposite pattern was found, with smaller individuals having higher body temperature and daytime heart rates. Body mass was associated with body temperature in the winter hypometabolic state, even in a large hibernating mammal. Smaller bears, which are known to have higher thermal conductance, reached lower body temperatures during hibernation. During summer, smaller bears had higher body temperatures and daytime heart rates, a phenomenon not previously documented within a single mammalian species.We conclude that the smallest bears hibernated more deeply and longer than large bears, likely from a combined effect of basic thermodynamics, the higher need for energy savings, and a lower cost of warming up a smaller body.
Englisch
2023
Dieses Werk bzw. dieser Inhalt steht unter einer
CC BY 4.0 - Creative Commons Namensnennung 4.0 International Lizenz.
CC BY 4.0 International
http://creativecommons.org/licenses/by/4.0/
Metabolic-Rate; Mammalian Hibernation; Daily Torpor; Black Bears; Energy Availability; Ursus-Arctos; Size; Selection; Medetomidine; Strategies