Sex-specific aggression and antipredator behaviour in young brown trout.

Ji. Johnsson et al., Sex-specific aggression and antipredator behaviour in young brown trout., ETHOLOGY, 107(7), 2001, pp. 587-599
Citations number
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ISSN journal
0179-1613 → ACNP
Year of publication
587 - 599
SICI code
Sex differences in adult behaviour are often interpreted as consequences of sexual selection and/or different reproductive roles in males and females. Sex-specific juvenile behaviour, however, has received less attention. Adu lt brown trout males are more aggressive than females during spawning and j uvenile aggression may be genetically correlated with adult aggression in f ish. We therefore tested the prediction that immature brown trout males are more aggressive and bolder than immature females. Because previous work ha s suggested that precocious maturation increases dominance in salmonids, we included precocious males in the study to test the prediction that early s exual maturation increase male aggression and boldness. Aggression and domi nance relations were estimated in dyadic contests, whereas boldness was mea sured as a response to simulated predation risk using a model heron. Indepe ndent of maturity state, males initiated more than twice as many agonistic interactions as females in intersexual contests. However, males were not si gnificantly more likely to win these contests than females. The response to a first predator attack did not differ between sex categories, but males r eacted less to a second predator attack than females. Sexual maturity did n ot affect the antipredator response in males. Since there is no evidence fr om field studies that stream-living immature male and female salmonids diff er in growth rate, it appears unlikely that the sex differences demonstrate d are behavioural consequences of sex-specific investment in growth. It see ms more likely that sex-specific behaviour arises as a correlated response to sexually selected gene actions promoting differential behaviour in adult males and females during reproduction. Alternatively, sex differences may develop gradually during juvenile life, because a gradual developmental pro gram should be less costly than a sudden behavioural change at the onset of sexual maturity.