A Middle Pleistocene hippo tracksite at Gombore II-2 (Melka Kunture, Upper Awash, Ethiopia)

In this paper we describe exceptionally well-preserved evidence of hippo activity at Gombore II-2, a 700,000 year-old site at Melka Kunture, at 2000 m asl in the Ethiopian highlands, in the Upper Awash Valley. We excavated and made casts of footprints that had been left after a volcanic eruption. The 3D casts provide a detailed record of the outer anatomy and soft tissues of Pleistocene hippos. They reveal for the first time the shape of the legs and feet of the animals. Gombore II-2 also provides information on the behavior of past hippos. This prominent species of the African wildlife affects the vegetation and the landscape, and acts as a geomorphological agent. The animals wallow beside bodies of water and erode deep trails linking them to pastures. At Gombore II-2 the trampling marks converge toward an erosional feature that we interpret as a fossil trail, documenting an early Middle Pleistocene behavior similar to that of today. Signs of trampling and erosional features interpreted as hippo trails have also been described in Pliocene and early Pleistocene levels at Olduvai and Koobi Fora. We further underline that the hippo population of this tract of the valley was resilient and re-established itself not long time after the volcanic eruption.