Vigilance in reindeer (Rangifer tarandus); evolutionary history, predation and human interference

Abstract

To elucidate genetic variability in vigilance behaviour for reindeer with historical differences in their interactions with predators and humans, we measured vigilance frequency and duration for grazing reindeer in Southern Norway (Rondane and Norefjell-Reinsjøfjell), Svalbard (Edgeøya and Nordenskiöld Land) and Barf/Royal Bay and Busen in the southern Hemisphere (South Georgia). Averaged for all areas, frequency and duration of vigilance bouts were less than 0.5 and 2.5 s, respectively. Frequency was insignificantly 1.3 times higher in Rondane than Edgeøya, and significantly 2.0, 3.5, 5.2 and 12.4 times higher than Norefjell, Nordenskiöld Land, Barf/Royal Bay and Busen, respectively. Duration per vigilance bout was not different amongst the areas. Thus, while frequency varied considerably, duration remained constant, supporting a hard-wired adaptation to, among other suggestions, an open landscape. Plasticity in frequency allows for flexible behavioral responses to environmental factors with predation, domestication and hunting key drivers for reindeer. Other factors include (1) the open, treeless alpine/Arctic environment inhabited by Rangifer subspecies allowing warning time, (2) grouping behaviour, (3) relative low density of predators and (4) the anatomy and physiology of ungulate vision.