The aim of this study is to investigate cellular mechanisms underlying Svalbard reindeer's ability to lower their body temperature in winter to save energy. To achieve this, we will collect muscle and heart tissue from culled reindeer in October as part of a larger field campaign. These samples will later be analysed for omega-6 fatty acids concentrations and their link to membrane-bound enzymes relevant for cold tolerance. Identifying such a mechanism may contribute to explain how and why the Svalbard reindeer are able to reduce their body temperature in winter and save energy under harsh environmental conditions.