Red Deer are a common sight in the highlands and islands of Scotland. It is the largest terrestrial mammal to be found in Scotland and one of the most impressive sightings. Large single sex groups tend to congregate, only mixing during the rutting season and these large groups may persist for most of the year. Red deer are active throughout the 24 hour period with peak times of activity at dawn and dusk. The deer are often found in the open hills during the day, especially in the summer months, descending to the shelter of the lower ground and forest during the night and in the winter months. A herd of semi-wild reindeer also frequent the northern Cairngorms and can often been see roaming the Cairngorm plateau. Roe deer are also fairly widespread around the lower slopes and woodlands.