Why fight? Socially dominant jackdaws, Corvus monedula, have low fitness

Zoological Laboratory of the University of Groningen, Netherlands
Animal Behaviour (Impact Factor: 3.07). 10/2004; DOI: 10.1016/j.anbehav.2003.12.020
Source: OAI

ABSTRACT Social dominance is intuitively assumed to be associated with higher fitness, because social dominance implies better access to resources. We found that, in a colony of jackdaws, the dominant males consistently produced fewer fledglings, which had lower chances of survival to 1 year of age. Laying date and clutch size were independent of dominance, but females that mated with dominant males were in poorer condition and laid smaller eggs. Parental survival was independent of social dominance, and the frequency of extrapair fertilizations in jackdaws is negligible. Dominance was a stable trait of individuals, and not a state that all individuals eventually attained. We conclude that, in this colony, dominant jackdaws had lower fitness. To our knowledge, this is the first example of such a pattern in a free-living species. We hypothesize that the high density of our colony resulted in high testosterone titres, which suppressed paternal care of mate and offspring to the extent that it outweighed the benefits of higher resource access.

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    ABSTRACT: Fighting is a fundamental determinant of male fitness in species where females prefer socially dominant males as mates or where dominants can prevent subordinates from mating. This in turn can lead to the evolution of honest inter- and intra-sexual cues of male dominance. Fighting as a behaviour comprises both fighting rate (number of fights per unit of time) and fighting performance (success in winning fights), but it is not always clear which of these components are important for female choice and how they link to signals of male quality. To quantify the relative importance of fighting as a cue for females, we recorded detailed behavioural data from male black grouse Tetrao tetrix at leks. We explored the relationship between phenotypic traits (body mass, eye comb size, tail (lyre) length and blue chroma colouration) and fighting performance and rates and how these were related to male mating success. In older males' pairwise fights, winners had lower blue chroma than losers, but there were no differences in other morphological traits. In yearlings, no morphological trait predicted success in pairwise contests. Both fighting rate and performance were positively related to the number of copulations acquired by a male; however, when controlled for lek centrality, fighting performance and not fighting rate was significantly related to mating success. Our results indicate that females may be using components of fighting behaviour as cues for mate choice.
    Behavioral Ecology and Sociobiology 12/2012; 66(12). · 3.05 Impact Factor
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    ABSTRACT: Developmental stressors often have long-term fitness consequences, but linking offspring traits to fitness prospects has remained a challenge. Telomere length predicts mortality in adult birds, and may provide a link between developmental conditions and fitness prospects. Here, we examine the effects of manipulated brood size on growth, telomere dynamics and post-fledging survival in free-living jackdaws. Nestlings in enlarged broods achieved lower mass and lost 21% more telomere repeats relative to nestlings in reduced broods, showing that developmental stress accelerates telomere shortening. Adult telomere length was positively correlated with their telomere length as nestling (r = 0.83). Thus, an advantage of long telomeres in nestlings is carried through to adulthood. Nestling telomere shortening predicted post-fledging survival and recruitment independent of manipulation and fledgling mass. This effect was strong, with a threefold difference in recruitment probability over the telomere shortening range. By contrast, absolute telomere length was neither affected by brood size manipulation nor related to survival. We conclude that telomere loss, but not absolute telomere length, links developmental conditions to subsequent survival and suggest that telomere shortening may provide a key to unravelling the physiological causes of developmental effects on fitness.
    Proceedings of the Royal Society B: Biological Sciences 04/2014; 281(1785):20133287. · 5.29 Impact Factor
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    ABSTRACT: Behaviour may contribute to changes in fitness prospects with age, for example through effects of age dependent social dominance on resource access. Older individuals often have higher dominance rank, which may reflect a longer lifespan of dominants, and / or an increase in social dominance with age. In the latter case, increasing dominance could mitigate physiological senescence. We studied the social careers of free-living jackdaws over a twelve-year period, and found that (i) larger males attained higher ranks, (ii) social rank increased with age within individuals, and (iii) high-ranked individuals had shorter lifespan suggesting that maintaining or achieving high rank and associated benefits comes at a cost. Lastly, (iv) social rank declined substantially in the last year an individual was observed in the colony, and through its effect on resource access this may accelerate senescence. We suggest that behaviour affecting the ability to secure resources is integral to the senescence process via resource effects on somatic state, where behaviour may include social dominance but also learning, memory, perception and (sexual) signalling. Studying behavioural effects on senescence via somatic state may be most effective in the wild, where there is competition for resources, which is usually avoided in laboratory conditions.
    Proceedings of the Royal Society B: Biological Sciences 08/2014; in press. · 5.29 Impact Factor

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