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  • Publication
    Accès libre
    Intra- and interspecific aggression do not modulate androgen levels in dusky gregories, yet male aggression is reduced by an androgen blocker
    Vullioud, Philippe
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    Ros, Albert Frank Huascar
    Discussions about social behavior are generally limited to fitness effects of interactions occurring between conspecifics. However, many fitness relevant interactions take place between individuals belonging to different species. Our detailed knowledge about the role of hormones in intraspecific interactions provides a starting point to investigate how far interspecific interactions are governed by the same physiological mechanisms. Here, we carried out standardized resident–intruder (sRI) tests in the laboratory to investigate the relationship between androgens and both intra- and interspecific aggression in a year-round territorial coral reef fish, the dusky gregory, Stegastes nigricans. This damselfish species fiercely defend cultivated algal crops, used as a food source, against a broad array of species, mainly food competitors, and thus represent an ideal model system for comparisons of intra-and interspecific territorial aggression. In a first experiment, resident S. nigricans showed elevated territorial aggression against intra- and interspecific intruders, yet neither elicited a significant increase in androgen levels. However, in a second experiment where we treated residents with flutamide, an androgen receptor blocker, males but not females showed decreased aggression, both towards intra- and interspecific intruders. Thus androgens appear to affect aggression in a broader territorial context where species identity of the intruder appears to play no role. This supports the idea that the same hormonal mechanism may be relevant in intra- and interspecific interactions. We further propose that in such a case, where physiological mechanisms of behavioral responses are found to be context dependent, interspecific territorial aggression should be considered a social behavior.
  • Publication
    Accès libre
    Negotiations over Grooming in Wild Vervet Monkeys (Chlorocebus pygerythrus)
    Van de Waal, Erica
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    Spinelli, Martina
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    Ros, Albert Frank Huascar
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    Noë, Ronald
    Mutual grooming plays a central role in the establishment and maintenance of social relationships in primates. Allogrooming has two main functions: hygiene and bonding with partners. The duration of grooming bouts is commonly used in studies of the functional aspects of grooming, but few reflect on the proximate mechanisms that determine grooming bout lengths. As it is highly unlikely that groomer and groomee prefer exactly the same bout length, we are likely to observe the result of some form of negotiation. We currently lack information about the signals that primates employ to inform others about their intentions and desires concerning grooming interactions. From October 2006 until April 2007 we studied three behaviors shown in grooming interactions that could potentially have a signaling function in the negotiation process over the initiation and length of grooming bouts among adult females of two vervet groups freely ranging in the Loskop Dam Nature Reserve, South Africa: approaching another individual as far as that resulted in a grooming session, changing of the body position by the groomed individual, and lip smacking. We found that “approach” did not reliably predict which individual would receive grooming first, although approaching individuals groomed significantly more than those approached. Thus, in the context of grooming interactions, moving toward a group member may signal the willingness to invest. Body part presentations appeared to be the main signal used to demand a prolongation of the grooming by the partner. Finally, lip smacking was used under potentially stressful circumstances, notably shortly before using the mouth to groom the partner or an attempt to touch a mother’s infant. Our exploratory study hopefully inspires colleagues to start looking at the role of communication during cooperative interactions for a better appreciation of how animals manage cooperation and negotiate exchange rates.