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AGONISTIC BEHAVIOR IN HARBOR SEALS ( PHOCA VITULINA ) IN RELATION TO THE AVAILABILITY OF HAUL‐OUT SPACE
Author(s) -
Neumann Dirk R.
Publication year - 1999
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.1999.tb00816.x
Subject(s) - agonistic behaviour , phoca , harbor seal , dominance (genetics) , competition (biology) , dominance hierarchy , ecology , biology , psychology , aggression , social psychology , biochemistry , gene
A bstract The hypothesis that haul‐out space is a contested resource among harbor seals ( Phoca vitulina ) was tested by comparing the number of agonistic interactions and the time devoted to them, at a haul‐out with unlimited space and a haul‐out with limited space, in Humboldt County, California. 798 agonistic interactions were recorded in 160 h of observation. The average number of agonistic interactions per seal per hour and the time spent on these interactions were significantly higher at the site with limited haul‐our space ( P < 0.05, n = 20). At this restricted site, the frequency of agonistic interactions was positively correlated with seal density ( r = 0.61, P < 0.05, n = 20), as was time spent on agonistic interactions ( r = 0.84, P < 0.05, n = 20). Size, sex, and age‐class of individuals all influenced agonistic interactions. In 72.5% of displacements, smaller seals were displaced by larger ones. This may support claims that some harbor seal populations maintain a size‐based dominance hierarchy. The results of this study support the hypothesis that there is competition among harbor seals for suitable haul‐out space where this resource is limited. The outcome of these interactions may be predicted, at least in part, by theoretical models on pay‐off asymmetries, resource holding power, and the prior residency effect.