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.

Download full-text


Available from: Simon Verhulst, Aug 30, 2015
  • Source
    • "But fast explorers might have to trade this off against the costs of heightened testosterone sensitivity, as is manifest during trade-offs with, for example, paternal effort (Ketterson et al. 1992, 1996). Individuals with high testosterone sensitivity could be worse fathers, since they are expected to desert at higher frequency and provide reduced rates of nestling feeding (Lynn et al. 2005) which consequently could decrease fitness (Verhulst & Salomons 2004; Duckworth 2006). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Keywords: aggression behavioural syndrome great tit Parus major phytohaemagglutinin testosterone Individuals within species differ in their behavioural reactions to the environment. Consistent individual differences in these behaviours (personality traits) are often correlated and known to be under natural selection. These differences are frequently associated with variation in physiological traits, such as endocrine profiles. For example, variation in circulating testosterone levels is associated with variation in several personality traits and has been hypothesized to be a marker for personality in humans and rodents. The importance of testosterone in controlling both behavioural strategies and individual physiological differences suggests that direct selection on personality traits might cause pleiotropic selection on the physiological mechanisms underlying these traits. To test this hypothesis, we quantified levels of plasma testosterone levels and measured phytohaemagglutinin (PHA)-induced immune responses of male great tits, Parus major, in lines artificially selected for diverging levels of avian personality ('fast' and 'slow' exploratory behaviour). We found that testosterone levels were highly repeatable within individuals and fluctuated predictably over the season. Contrary to our expectations, 'slow' explorers had consistently higher levels of baseline testosterone and higher immune responses than 'fast' explorers. These results show that phenotypic selection for variation in personality traits corresponds to consistent differences in hormone profile and immune function, but that higher aggression levels do not need to be associated with higher baseline testosterone levels. Our results confirm that personality traits have evolved as a result of selection on both the underlying controlling physiological mechanisms and the phenotypic traits.
    Animal Behaviour 04/2011; 81(5). DOI:10.1016/j.anbehav.2011.02.014 · 3.14 Impact Factor
  • Source
    • "In organisms that might loosely be classified as displaying higher levels of 'sociality' (Costa & Fitzgerald, 2005), it is also common for dominant individuals to monopolize reproduction and receive benefits from subordinate helpers (Clutton- Brock et al., 2001). Thus, social dominance is generally viewed as being under positive selection, although empirical studies have highlighted that exceptions can and do occur (Ellis, 1995; Qvarnströ m & Forsgren, 1998; Verhulst & Salomons, 2004). A critical requirement for adaptive evolution is that trait variation within populations is, at least in part, caused by heritable differences among individuals. "
    [Show abstract] [Hide abstract]
    ABSTRACT: By determining access to limited resources, social dominance is often an important determinant of fitness. Thus, if heritable, standard theory predicts mean dominance should evolve. However, dominance is usually inferred from the tendency to win contests, and given one winner and one loser in any dyadic contest, the mean proportion won will always equal 0.5. Here, we argue that the apparent conflict between quantitative genetic theory and common sense is resolved by recognition of indirect genetic effects (IGEs). We estimate selection on, and genetic (co)variance structures for, social dominance, in a wild population of red deer Cervus elaphus, on the Scottish island of Rum. While dominance is heritable and positively correlated with lifetime fitness, contest outcomes depend as much on the genes carried by an opponent as on the genotype of a focal individual. We show how this dependency imposes an absolute evolutionary constraint on the phenotypic mean, thus reconciling theoretical predictions with common sense. More generally, we argue that IGEs likely provide a widespread but poorly recognized source of evolutionary constraint for traits influenced by competition.
    Journal of Evolutionary Biology 02/2011; 24(4):772-83. DOI:10.1111/j.1420-9101.2010.02212.x · 3.48 Impact Factor
  • Source
    • "Behavioural interactions can influence individual success through their impact on the physiology and health of breeding individuals. When species compete for resources it can have negative effects on all involved regardless of dominance rank (Verhulst and Salomons 2004, Poisbleau et al. 2005). Interactions with heterospecifics take time away from fitness associated activities, such as foraging, mating or offspring defence. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Maternal effects are increasingly being recognized as an important pre-natal source of life history variation in the next generation. The present study uses a field experiment to explore the influence of heterospecific interactions on the reproductive output and offspring characteristics of a common Indo-Pacific damselfish, Pomacentrus amboinensis. On the Great Barrier Reef pairs of breeding P. amboinensis were placed on isolated patch reefs and to half of the pairs resource competitors (other planktivorous damselfishes), and predators of eggs and juveniles were added. Females inhabiting patches with heterospecifics had more aggressive interactions and higher levels of the stress hormone, cortisol. Neither the number of clutches nor number of eggs produced differed among treatments. The size of larvae at hatching was found to be reduced as a result of the stress associated with increased interactions with heterospecific and the transfer of cortisol to offspring. This stress-associated mechanism appears to be an important and directional source of life history variability, but the individual nature of the maternal response is likely to result in a conclusion of a diversified bet hedging reproductive strategy when viewed at the local population level. These findings highlight the complex determinants of individual success and the important role of parental well-being in the population dynamics of the next generation.
    Oikos 05/2009; 118(5):744-752. DOI:10.1111/j.1600-0706.2008.17410.x · 3.56 Impact Factor
Show more