Reindeer 24-hr within and between group synchronicity in summer versus environmental variables

• Published in: Rangifer
• Main Authors: Jonathan E. Colman, Ruben Eidesen, Dag Hjermann, Mathis A. Gaup, Øystein Holand, Stein R. Moe, Eigil Reimers
• Format: Article in Journal/Newspaper
• Language: English
• Published: Septentrio Academic Publishing 2004
• Subjects: activity; behaviour; circadian rhythm; feeding; light; Rangifer tarandus; Animal culture; SF1-1100; Rangifer
• Online Access: https://doi.org/10.7557/2.24.1.298; https://doaj.org/article/a859aede0ad84e62a38aed31cf2a8775

Abstract: The impact of abiotic stimuli on the circadian activity rhythm of Rangifer has long been debated. Their highly gregarious and mobile behaviour presupposes synchronized behaviour within a group, while a predominant abiotic influence would be expected to synchronize separate, independent groups subjected to the same environment. We tested within and between group synchronization of semi-domestic reindeer during summer observing 6 independent groups located in close proximity to each other. We also tested how some external environmental factors affected the animals’ behaviour. Activity of all individuals (3 females in 6 groups, n = 18 reindeer) was recorded every 10 minutes 24-hrs a day, along with weather variables and biotic factors such as insect harassment. Data were divided into two periods of 8 and 6 days, respectively, separated by a period of 6 days. Animals within a group showed highly synchronized behaviour, reflected in overlapping periods of grazing and ruminating. There was little or no synchronization between groups, reflected by little or infrequent overlapping of activities amongst some of the groups. Rarely were all 6 groups active or inactive simultaneously. There was no consistent or significant influence on the reindeers’ behaviour by any of the environmental variables recorded. Thus, and as expected, in the absence of external environmental stimuli, the activity of individuals within a group was synchronized. However, there was no synchronization amongst independent groups. This supports the claim that during summer, in the absence of disturbance from stimuli such as insect harassment or anthropogenic activities, reindeer have a 24-hr polycyclic activity rhythm independent of climatic variables. Instead of abiotic factors, such as light, reindeers’ activity rhythms were defined by internal physiological processes and intra-specific group interactions reflected in almost complete within group synchronization and lack of between group synchronization. Abstract in Norwegian / Sammendrag: ...