describe its social behavior?
They were herding animals, due to the large number of known bone beds containing multiple members of the same ceratopsian species.
Achelousaurus
It has been claimed that ceratopsian dinosaurs were herding animals, due to the large number of known bone beds containing multiple members of the same ceratopsian species. In 2010, Hunt and Farke pointed out that this was mainly true for centrosaurine ceratopsians. Horner assumed that the horned dinosaurs at Landslide Butte lived in herds which had been killed by drought or disease. Dodson concluded that the fact that the "Achelousaurus" bone beds were monospecific (containing only one species) confirmed the existence of 
what is achelousaurus? It is a genus of centrosaurine ceratopsid dinosaur.
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Achelousaurus [SEP] Social behavior
It has been claimed that ceratopsian dinosaurs were herding animals, due to the large number of known bone beds containing multiple members of the same ceratopsian species. In 2010, Hunt and Farke pointed out that this was mainly true for centrosaurine ceratopsians. Horner assumed that the horned dinosaurs at Landslide Butte lived in herds which had been killed by drought or disease. Dodson concluded that the fact that the "Achelousaurus" bone beds were monospecific (containing only one species) confirmed the existence of herds.