FIELD ANALYSIS OF THE DOMINANCE HIERARCHY 



OF THE BICOLOR DAMSELFISH 



STEGASTES PARTITUS (POEY) (PISCES: POMACENTRIDAE) 



Yvonne Sadovy* 

 Department of Zoology 

 University of Manchester 

 Manchester, M13 9PL England 



ABSTRACT 



The dominance relations of the damselfish Stegastes partitus were examined 

 in the field. The dominance hierarchy, based on aggressive interactions, was 

 linear and size-dependent, with most aggression between individuals most similar 

 in size and least between those most dissimilar in size. These results show 

 both similarities to and differences from results obtained in a very similar 

 earlier study on the same species but conducted entirely in the laboratory. 

 The importance of field studies in assessing the degree of reliability of 

 results obtained under artificial conditions is emphasized. 



INTRODUCTION 



Many species of animals display a dominance hierarchy among members of 

 social units. A group of animals may be said to have a dominance hierarchy if 

 the interactions between individuals allow some to have priority over others 

 under certain circumstances. The most simple hierarchy is defined as follows: 

 individual A dominates all members of a group; another animal B dominates all 

 members except A, and so on to the last member, omega, which dominates no other 

 individuals. If this relationship holds, then the hierarchy is said to be 

 linear (Chase, 1974). 



Considerable research has examined the dominance relations of a wide 

 variety of animal species. However, the majority of studies have been conducted 

 in the laboratory or under other artificial conditions. In studies carried out 

 both in the field and in the laboratory on the same species, there often have 

 been discrepancies in the conclusions. Thompson (1960) found that laboratory 

 populations of house finches had a hierarchy dominated by females, but that 

 field populations did not show this pattern. In some primates, a different 

 form of social structure was evident between captive animals and the same 

 species in the field (Rowel 1, 1967; Hinde, 1974). In the baboon, Papio anubis , 

 interactions were about four times as frequent among captive animals as among 

 individuals observed in the field (Rowel 1, 1967). Among the fishes, Myrberg 

 (1972aJ conducted a field and laboratory study of territoriality and social 

 hierarchy in the bicolor oamselfish (Pomacentridae) , Stegastes (= Eupomacentrus ) 



1 Present address: Department of Marine Sciences, University of Puerto 

 Rico, Mayaguez, Puerto Rico 00708. 



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