Svalbard reindeer population size and trends in four sub-areas of Edgeøya

In summer 2006 Svalbard reindeer (Rangifer tarandus platyrhynchus) in south-western Edgeøya (Plurdalen, Grunnlinjesletta, Siegelfjellet and Burmeisterfjellet) showed a low population (181 animals) and recruitment rate, in terms of both calves (9.4%) and yearlings (1.2%). The low recruitment rates were not accompanied by high winter mortality: of only five carcasses found, none were calves born in 2005. A comparison with survey data from 1969 in a restricted part of the study area (Plurdalen and Grunnlinjesletta) shows a consistently low recruitment rate since 1975, indicating a stable or slowly decreasing population

Kelp and seaweed feeding by High-Arctic wild reindeer under extreme winter conditions

One challenge in current Arctic ecological research is to understand and predict how wildlife may respond to increased frequencies of “extreme” weather events. Heavy rain-on-snow (ROS) is one such extreme phenomenon associated with winter warming that is not well studied but has potentially profound ecosystem effects through changes in snow-pack properties and ice formation. Here, we document how ice-locked pastures following substantial amounts of ROS forced coastal Svalbard reindeer (Rangifer tarandus platyrhynchus) to use marine habitat in late winter 2010. A thick coat of ground ice covered 98% of the lowland ranges, almost completely blocking access to terrestrial forage. Accordingly, a population census revealed that 13% of the total population (n=26 of 206 individuals) and 21% of one sub-population were feeding on washed-up kelp and seaweed on the sea-ice foot. Calves were overrepresented among the individuals that applied this foraging strategy, which probably represents a last attempt to avoid starvation under particularly severe foraging conditions. The study adds to the impression that extreme weather events such as heavy ROS and associated icing can trigger large changes in the realized foraging niche of Arctic herbivores

Cratering behaviour and faecal C:N ratio in relation to seasonal snowpack characteristics in a High-Arctic ungulate

Snow and ice determine winter forage availability for Arctic herbivores. Winter precipitation is anticipated to increase, and icing following warm spells and rain-on-snow (ROS) are likely to become more frequent. While this may reduce herbivore survival, fecundity and population growth, we can also expect behavioural and dietary responses. Here, we tested predictions from optimal foraging theory on how changing snowpack conditions influence choice of feeding craters and diet quality in a large generalist herbivore, the wild Svalbard reindeer. Snow and ice conditions over winter 2012/13 (a ‘normal’ winter with little ROS and icing) were measured in reindeer feeding craters, in paired controls one metre away and in fixed control sites. On average, feeding craters had less snow and integrated ram hardness (IRH, the force needed to reach the ground), but not less ice, than nearby controls. However, on this fine spatial scale, reindeer tended to select for microhabitat with worse snowpack conditions up to a certain level of snow (ca. 10 cm), ice (0.5 cm) and IRH (250 kg cm) in the nearby controls, reflecting the trade-off between selection for forage abundance versus accessibility in a sparsely vegetated environment. In this lichen-free system, faecal C:N ratios increased during winter as forage accessibility was increasingly restricted by snow, possibly indicating a reduction in diet quality due to changes in diet composition. Our study suggests that snowpack depth and hardness largely determine Svalbard reindeer feeding behaviour and diet quality during the course of a winter season