Electronic versions

DOI

  • Floris M van Beest
    Department of Ecoscience, Aarhus University, Roskilde, Denmark
  • Larissa T Beumer
    Department of Ecoscience, Aarhus University, Roskilde, Denmark
  • Marianna Chimienti
    Department of Ecoscience, Aarhus University, Roskilde, Denmark
  • Jean-Pierre Desforges
    Department of Ecoscience, Aarhus University, Roskilde, Denmark
  • Nicholas Per Huffeldt
    Department of Ecoscience, Aarhus University, Roskilde, Denmark
  • Stine Højlund Pedersen
    Department of Biological Sciences University of Alaska Anchorage Anchorage AK USA.
  • Niels Martin Schmidt
    Department of Ecoscience, Aarhus University, Roskilde, Denmark

The existence and persistence of rhythmicity in animal activity during phases of environmental change is of interest in ecology, evolution and chronobiology. A wide diversity of biological rhythms in response to exogenous conditions and internal stimuli have been uncovered, especially for polar vertebrates. However, empirical data supporting circadian organization in behaviour of large ruminating herbivores remains inconclusive. Using year-round tracking data of the largest Arctic ruminant, the muskox (Ovibos moschatus), we modelled rhythmicity as a function of behaviour and environmental conditions. Behavioural states were classified based on patterns in hourly movements, and incorporated within a periodicity analyses framework. Although circadian rhythmicity in muskox behaviour was detected throughout the year, ultradian rhythmicity was most prevalent, especially when muskoxen were foraging and resting in mid-winter (continuous darkness). However, when combining circadian and ultradian rhythmicity together, the probability of behavioural rhythmicity declined with increasing photoperiod until largely disrupted in mid-summer (continuous light). Individuals that remained behaviourally rhythmic during mid-summer foraged in areas with lower plant productivity (NDVI) than individuals with arrhythmic behaviour. Based on our study, we conclude that muskoxen may use an interval timer to schedule their behavioural cycles when forage resources are low, but that the importance and duration of this timer are reduced once environmental conditions allow energetic reserves to be replenished ad libitum. We argue that alimentary function and metabolic requirements are critical determinants of biological rhythmicity in muskoxen, which probably applies to ruminating herbivores in general.

Original languageEnglish
Pages (from-to)201614
JournalRoyal Society Open Science
Volume7
Issue number10
Early online date28 Oct 2020
DOIs
Publication statusPublished - 31 Oct 2020
Externally publishedYes
View graph of relations