The Mammoth Tribe is one of the Ice Hunter Tribes from the summer 2014 range. The only members available in LEGO sets are Maula, Mungus and Mottrot. Coincidently, they all happen to be in the same family.
During season 3, the Mammoth Tribe was a member of the "ice tribes" or "Hunters", and its members had the symbol shown left on their vehicles and clothes.
Oddly, the tribe is titled the Mammut Tribe on LEGO.com. Whether that is the official name or a typo is unknown. However, this name may be referring to Mammuthus, the genus that mammoths are classified as.