Reindeer. Male (bull) reindeer ( IRangifer i Itarandus i). A fully grown reindeer (also known as a caribou) can weigh up to 320 kg and have a body length of up to 2 metres. Reindeers are herbivores that live in large herds and migrate twice a year. In summer they graze in the northern parts of their range, in winter they head south. The male reindeer's antlers are very large, branched and asymmetrical. The antlers are shed every year and their growth is controlled by sex hormones. Reindeers live in Arctic tundra and range from Scandinavia to Asia and northern North America. Photographed in Denali National Park, Alaska, USA.