Deep body temperature was recorded in two female Svalbard reindeer during summer and winter. The reindeer were subjected to naturally occurring weather, photoperiod and stimuli in outdoor pens on Svalbard. A telemetry system was employed using transmitters ingested into the rumen. Mean deep body temperature was 0.3°C higher in winter and while the animals were lying down. This suggests a different strategy for thermoregulation than that employed by other reindeer subspecies.