Abstract
For free-ranging animals living in seasonal environments, hypometabolism (lowered metabolic rate) and hypothermia (lowered body temperature) can be effective physiological strategies to conserve energy when forage resources are low. To what extent such strategies are adopted by large mammals living under extreme conditions, as those encountered in the high Arctic, is largely unknown, especially for species where the gestation period overlaps with the period of lowest resource availability (i.e. winter). Here we investigated for the first time the level to which high arctic muskoxen (Ovibos moschatus) adopt hypothermia and tested the hypothesis that individual plasticity in the use of hypothermia depends on reproductive status. We measured core body temperature over most of the gestation period in both free-ranging muskox females in Greenland and captive female muskoxen in Alaska. We found divergent overwintering strategies according to reproductive status, where pregnant females maintained stable body temperatures during winter, while non-pregnant females exhibited a temporary decrease in their winter body temperature. These results show that muskox females use hypothermia during periods of resource scarcity, but also that the use of this strategy may be limited to non-reproducing females. Our findings suggest a trade-off between metabolically-driven energy conservation during winter and sustaining foetal growth, which may also apply to other large herbivores living in highly seasonal environments elsewhere.
Highlights
In study period Calf at Date of heel? parturitionc No 2018-04-16 No 2018-03-25 No 2018-04-25 No 2018-05-07 No 2018-04-29 No 2018-04-28 Yes No birth event Yes No birth event No No birth event No No birth event
Our study clearly shows that Tb of female muskoxen in the high Arctic varies markedly across the year, and some females displayed lowered body temperature during periods of resource scarcity
This suggests that muskoxen can adopt hypothermia as an over-wintering strategy to conserve energy
Summary
In study period Calf at Date of heel? parturitionc No 2018-04-16 No 2018-03-25 No 2018-04-25 No 2018-05-07 No 2018-04-29 No 2018-04-28 Yes No birth event Yes No birth event No No birth event No No birth event. Muskoxen rely heavily on energy reserves accumulated over the previous snow-free period[18]. We hypothesize that hypothermia as an over-wintering strategy in free-ranging muskoxen may interfere with maintenance of foetal growth. As a capital breeder[20], muskoxen must rely on their energy reserves to cover maintenance and costly reproductive needs as the food-constrained period coincides with the c. Faced with the severe resource limitations during winter and the concurrent need for pregnant females to support foetal growth, we expect muskoxen to conserve energy through lowered body temperatures, and expect that the level of hypothermia to depend on reproductive status, such that non-pregnant females reduce body temperatures more than pregnant females
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
