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.

Keywords:

• interspecific associations
• fish-eating birds
• Lontra longicaudis
• Phalacrocorax brasilianus
• South America

Acknowledgements

We thank the staff of the “Parque Ecológico Prof. Hermógenes de Freitas Leitão Filho” for allowing us to study birds at the park and for the maintenance of the bank vegetation; Cristina Sazima for suggestions that improved the manuscript; Margaret Koopman, Pinthip Kerdplanun and Supharat Roopsuay for kindly sending hard to find references; Marlies Sazima, Celso L. D’Angelo and Micael E. Nagai for their constant support; Celso L. D’Angelo also for reading the manuscript; two anonymous reviewers for their suggestions; the Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq for earlier financial support to IS, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES for a postgraduate grant to GBD.