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  • Peignier, Mélissa; Pokorny, Tamara; Heinze, Jürgen; Lindgren, Rosanna; Helanterä, Heikki; Schultner, Eva (2019)
    Social insects live in highly complex societies with efficient communication systems. Begging is one display commonly used by offspring to signal their nutritional state, however begging behavior has received very little attention in social insects. Theory predicts that begging can be either an honest (i.e., honest-signaling strategy) or a dishonest (i.e., scrambling competition) signal of need, with dishonest signals expected to be more likely when relatedness within the group is low. To investigate the presence and honesty of begging, as well as the nature of the involved signals, we used a comparative approach with four species of the ant genus Formica known to differ in the degree of intra-colony relatedness. We investigated the behavior of starved and non-starved larvae of F. aquilonia, F. pressilabris (both low intra-colony relatedness), F. exsecta (intermediate relatedness), and F. fusca (high relatedness). In addition, we assessed the attraction of conspecific workers toward odors extracted from these two classes of larvae and analyzed the larval cuticular hydrocarbon profiles. We found that in F. fusca and F. exsecta, larvae signaled significantly more when starved. In contrast, larvae of F. aquilonia signaled significantly more when they were non-starved, while there was no significant difference in the behavior of starved vs. non-starved larvae in F. pressilabris. Our results show that workers were not preferentially attracted to the odor of starved larvae, and we also did not detect any differences between the cuticular hydrocarbon profiles of starved and non-starved larvae. Overall, this study demonstrates among species variation in larval hunger signaling in Formica ants, and encourages further studies to confirm the link between kin structure variation and the honesty of begging signals.
  • Tanskanen, Antti O.; Danielsbacka, Mirkka; Jokela, Markus; Rotkirch, Anna (2017)
    Sibling relations are by nature ambivalent with high levels of both altruistic helping and competition. Higher relatedness is often assumed to reduce the occurrence of conflicts between siblings, but evidence of this has been scarce and mixed. Siblings typically compete over resources and parental attention, and parental constellations vary with sibship types. Since full-siblings compete over the same two biological parents, while half-siblings have only one shared biological parent and often a higher number of parents overall, it is hypothesized that conflicts are more common between full- than half-siblings. This study tested this assumption using the British Millennium Cohort Study (n=7527 children at age 11). Conflicts were measured as children's reports of how much siblings picked on and hurt each other. Households with full-siblings only, maternal half-siblings only, and both full- and maternal half-siblings were compared. The results show that children who were living with only their full-siblings were more likely to experience sibling conflicts compared with children living with their maternal half-siblings only. This was the case also after controlling for several potentially confounding variables. The results suggest that differential access to parental resources of available biological and step-parents may explain the higher amount of sibling conflict between full- compared with maternal half-siblings.