Mice on menu: opportunistic feeding behaviour of the Amazonian silver arowana Osteoglossum bicirrhosum.

Two silver arowana, Osteoglossum bicirrhosum, one male (49.5 cm standard length, L ) and one female (52.5 cm L ) that had fed on small-eared colilargo or small-eared pygmy rice rat Oligoryzomys microtis, were sampled during the rising water period in the Brazilian Amazon. The identified prey were 6 and 8 cm long and occupied the entire stomachs of both individuals. This opportunistic feeding behaviour appears to be a strategy for this fish to acquire nutrients during times when its usual aquatic prey is dispersed throughout the flooded forest.