acta ethologica

, Volume 10, Issue 1, pp 23–28 | Cite as

Intra-sexual female agonistic behaviour of the South American sea lion (Otaria flavescens) in two colonies with different breeding substrates

  • Esteban Fernández-Juricic
  • Marcelo H. Cassini
Original Paper


Female agonistic behaviour during pregnancy and lactation is common in several pinnipeds and has been associated to pup or territory defence. Previous studies on female agonistic behaviour in pinniped breeding groups have not usually considered the number of females per breeding group, which could influence the degree of aggressiveness. We compared female agonistic behaviour (open-mouth displays and bites) within two colonies with different breeding substrates (homogeneous, Punta Norte; heterogeneous, Pirámide) of South American sea lions using two methods: weighted means and general linear models. We found that both aggressive interaction rates were significantly affected by female density, which accounted for a greater proportion on the variability in bite rates than in open-mouth rates. Controlling for the number of females, we found with both methods that open-mouth rates were higher than bite rates within the Pirámide colony; however, no differences were found within the Punta Norte colony. In Pirámide, open-mouth rates could be used more often as threats to minimise the chances of more severe aggressions. The conclusion is that females vary their use of agonistic interactions in relation to their density in the colony with heterogeneous substrate, which may be related to the presence of limited numbers of tide pools that heightens competition for thermoregulatory resources.


Otaria flavescens Pinnipeds Breeding groups Female aggression Otariids Patagonia 



We deeply thank Claudio Campagna for his feedback and fruitful discussions about the behavioural ecology of South American sea lions. EFJ was supported by the College of Natural Sciences and Mathematics, California State University Long Beach. MHC was funded by the Consejo Nacional de Investigaciones Cientificas y Tecnicas and the Agencia Nacional de Promoción Científica y Tecnológica. Behavioural observations complied with the current laws of the country in which they were performed.


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Copyright information

© Springer-Verlag and ISPA 2007

Authors and Affiliations

  • Esteban Fernández-Juricic
    • 1
  • Marcelo H. Cassini
    • 2
    • 3
  1. 1.Department of Biological SciencesCalifornia State University Long BeachLong BeachUSA
  2. 2.Departamento de Ciencias BásicasUniversidad Nacional de LujánLujánArgentina
  3. 3.Fundación PROFAUNABuenos AiresArgentina

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