acta ethologica

, Volume 21, Issue 2, pp 141–145 | Cite as

Potentially infanticidal behavior in the Amazon river dolphin (Inia geoffrensis)

  • Mark T. Bowler
  • Brian M. Griffiths
  • Michael P. Gilmore
  • Andrew Wingfield
  • Maribel Recharte
Short Communication


Infanticide by males is a phenomenon common in species in which the reproductive output of large numbers of females can be monopolized by a small number of males. It is thought to increase a male’s fitness, at the expense of the fitness of the infant’s parents, by bringing females into season more quickly. Infanticide by males has been recorded in just three cetacean species. We report aggressive behavior suggestive of infanticide in a fourth, the Amazon river dolphin (Inia geoffrensis). We observed and photographed a series of attacks on a neonate Amazon river dolphin by a large male, with apparent protective behavior by the mother. Although infanticide was not confirmed, the forceful, aggressive behaviors were highly suggestive of infanticidal behavior and represent another important data point for comparative studies of infanticide in mammals. Amazon river dolphins may have a polygynous, polyandrous, or promiscuous mating system, the latter two of which are not the norm in species in which the reproductive output of large numbers of females are monopolized by a small number of males. However, sexual dimorphism, high rates of aggression by males, socio-sexual object-carrying displays by males, and a long interbirth interval suggest that successful male Amazon river dolphins may be able to monopolize a large proportion of mating opportunities, and it is plausible that male dolphins can improve their reproductive success by bringing females into estrous sooner by killing the offspring of other males.


Infanticide Dolphin Aggression Pink dolphin Reproduction 



We thank Pam Bucur and the staff of Amazon Explorama Lodges for their assistance with logistics during our observations. We thank the editors and two anonymous reviewers for their detailed and helpful comments on our manuscript.

Compliance with ethical standards

All applicable international, national, and institutional guidelines for the care and use of animals were followed.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature and ISPA 2018

Authors and Affiliations

  1. 1.The School for Field StudiesBeverlyUSA
  2. 2.San Diego Zoo Global Institute for Conservation ResearchEscondidoUSA
  3. 3.Environmental Science and PolicyGeorge Mason UniversityFairfaxUSA
  4. 4.School of Integrative StudiesGeorge Mason UniversityFairfaxUSA
  5. 5.Psychology, School of Natural SciencesUniversity of StirlingStirlingUK

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