Congruent responses to weather variability in high arctic herbivores

Abstract

Assessing the role of weather in the dynamics of wildlife populations is a pressing task in the face of rapid environmental change. Rodents and ruminants are abundant herbivore species in most Arctic ecosystems, many of which are experiencing particularly rapid climate change. Their different life-history characteristics, with the exception of their trophic position, suggest that they should show different responses to environmental variation. Here we show that the only mammalian herbivores on the Arctic islands of Svalbard, reindeer (Rangifer tarandus) and sibling voles (Microtus levis), exhibit strong synchrony in population parameters. This synchrony is due to rain-on-snow events that cause ground ice and demonstrates that climate impacts can be similarly integrated and expressed in species with highly contrasting life histories. The finding suggests that responses of wildlife populations to climate variability and change might be more consistent in Polar regions than elsewhere owing to the strength of the climate impact and the simplicity of the ecosystem.

The influence of weather conditions during gestation on life histories in a wild Arctic ungulate

“…Age at last observation was retained in the model independent of its statistical significance. To further characterize the breeding environment, we included ROS in the previous winter (ROS current ) as this is strongly negatively associated with reproductive success [42]. ROS current was fitted as a continuous variable after a log þ 1 transformation to reduce nonlinearity [42].…”

“…To further characterize the breeding environment, we included ROS in the previous winter (ROS current ) as this is strongly negatively associated with reproductive success [42]. ROS current was fitted as a continuous variable after a log þ 1 transformation to reduce nonlinearity [42]. We tested whether ROS utero affected late-life reproductive success through differences in costs of early reproduction by re-running our previously selected model of reproductive success with the three-way interaction of the proportion of years in which a female produced a calf between age at first reproduction and 6 years old, ROS utero , and age.…”

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

“…Precipitation that fell at air temperatures above 1°C was considered rain (see, e.g., Stien et al 2012). Winter was defined as October in year t − 1 to April in year t.…”

“…Insect harassment is minimal (Reimers 1980), as is interspecific competition: the Svalbard rock ptarmigan (Lagopus muta hyperborea) is the only other over-wintering herbivore. Survival and reproduction rates are highly variable between years (Solberg et al 2001;Stien et al 2012) because of density-dependence and variation in climatic conditions during winter (Reimers 1983;Aanes et al 2000;Solberg et al 2001;Kohler & Aanes 2004;Hansen et al 2011;Hansen et al 2013), but also during summer (Aanes et al 2002;Hansen et al 2013). …”

“…In the High Arctic, where vegetation is generally of very low stature, ground ice can completely cover the vegetation (Hansen et al 2010). Such feeding conditions can lead to starvation-related declines in winter body mass , survival (Solberg et al 2001) and fecundity (Stien et al 2012), with consequences for population dynamics (Parker et al 1975;Kohler & Aanes 2004;Grenfell & Putkonen 2008;Miller & Barry 2009;Hansen et al 2011;Hansen et al 2013).…”