By Ingrid Paulsen
The High Arctic Archipelago of Svalbard is situated about 700 km north of Norway, half way to the North pole, in the Barents Sea. On this remote island group, the endemic Svalbard reindeer, the smallest of all Rangifer subspecies, has evolved in an environment with limited predation and insect harassments, or hunting and other human disturbances. Although studies on the Svalbard reindeer goes back to 1829, knowledge about where and when the critical stage of calving occurs is limited. Inaccessibility of calving areas during snow melt and reindeer shyness during this period makes it difficult for researchers to study calving in the field.
Today, decadal-long time series of female GPS data allows us to disentangle the behaviour and site fidelity of Svalbard reindeer through all seasons, including the calving period in June. The calving period is a vulnerable life stage for reindeer. However, since predation is virtually absent for the Svalbard reindeer, we wondered whether Svalbard reindeer select calving areas based on only forage resources or reminiscent anti-predation strategies, as observed in other ungulates.
To find out, we investigated habitat selection during calving by identifying the calving time and location for individual female reindeer using movement metrics from GPS-collared female reindeer. We paired their subsequent GPS locations after calving day with landscape features derived from remote sensed satellite data to get an idea of whether calving areas are different from available, surrounding habitat. For comparison, we also investigated habitat selection of females without calves after median population calving day in the same period.
Females with and without calves selected flat, lowland areas with high proportions of moss tundra and heath, i.e. habitat typical rich in foraging plants, in the calving period. Although the female reindeer selected for similar landscape features in the spring, many pregnant females showed directed movement towards past used calving locations and were on average closer in distance to these calving locations.
To us, this behaviour sheds light on a paradox – why would female with and without calves show similar habitat selection, but only females with calves display site fidelity to past calving areas? Is this behaviour due to innate traits and anti-predation strategies or simply because these females are ‘homing in’ on an area with better foraging resources? Read further for new insights into the secret life of this High Arctic reindeer.
All photos taken by Sophie Cordon.