Totemism is the belief that each group or tribe is related to a totem, most often an animal. Wolf and deer are the most frequent totems. Genghis Khan's line is supposed to come from these two animals.
The deer is mostly represented in the sculptures of Bronze Age, especially the monuments found in Northern country. The famous felt embroidery found in Noyon Uul's tomb, dating from Huns, proves the religious symbolism of the worship of deer.
The wolf is less commonly represented in prehistorical art, but regarding the wolf as a sacred creature is a custom that still exists today. It's a good omen to meet a wolf, especially during a trip or when you're searching lost cattle. Although today wolves can be killed to protect the cattle, killing a wolf has been considered as a taboo for a long time.
The worship of bears was also very commun among some ethnic groups, especially for Eastern Siberia's people, for whom the bear was the main totemic symbol. Old Mongolians are said to have worshiped bears: they used to fasten a picture of a bear's head on the posts of their house and to dance around it.