Commensal association of piscivorous birds with foraging otters in southeastern Brazil, and a comparison with such a relationship of piscivorous birds with cormorants

Abstract

Associations of birds with foraging otters are restricted to four records in different regions of the world. We report herein on piscivorous birds associated with foraging otters (Lontra longicaudis) in a pool at an urban park in southeastern Brazil. We recorded up to ˜30 individuals of seven piscivorous bird species associated with a single otter. The mammals searched for fish prey in the pool, causing fish to surface or flee to the shallows, and the birds preyed on the disturbed fish. The bird assemblages we recorded associated with otters are the richest ones reported to date both in number of species and individuals. The bird species associated with otters were the same that followed cormorants (Phalacrocorax brasilianus) in a large pond adjacent to the pool. The foraging of cormorants and otters may be considered as functionally equivalent, because both predators chase prey underwater, surface periodically, and cause fish to flee.