Reduced forage access affects home range size and site fidelity of Svalbard reindeer (Rangifer tarandus platyrhynchus)

Abstract

The Arctic is currently warming and this trend is expected to continue. This will lead to increased frequency and spatial extent of rain on snow events which cause ground ice to form. In this extreme and marginal environment, ground ice can have detrimental effects on the species living there. The objective of this study was to investigate how environmental conditions impact seasonal variation in the home ranges of individually marked Svalbard reindeer, in terms of home range size and site fidelity. To accomplish this, GPS data from female Svalbard reindeer in three valleys on Svalbard was combined with information on seasons and icing events. Ground icing was determined based on data from ground temperature loggers, precipitation data and field data on ice thickness. Included in the study were two winters with icing events, 2009/2010 and 2011/2012, and two without, 2010/2011 and 2012/2013. Home ranges were calculated with a 95 % fixed kernel estimator and site fidelity was measured as percent overlap of seasonal polygon home ranges. The reindeer had larger seasonal home ranges and displayed less site fidelity during the winter than during the summer. Winter home ranges were larger during years with icing events, compared to winters without. There was no correlation between calf status and home range size or site fidelity, or between age and site fidelity. Animals aged four to seven years had larger home ranges than younger (2-3 years) and older (8-11 years) reindeer. Svalbard reindeer seem to use small ranges as long as there is enough forage. They expand their home ranges in search for forage due to variations of food accessibility caused by extreme weather events. In a warming Arctic, this behavioral plasticity may be able to buffer the effects of increased rain on snow events on a small spatial scale.