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Intraspecific social dominance hierarchies should be influenced by environmental variation; however, in colour polymorphic species, dominance hierarchies are often assumed fixed, and thus insensitive to environmental variability. We ran a series of experiments using the colour polymorphic long-tailed brush lizard (Urosaurus graciosus) to challenge this assumption. We staged contests between orange and yellow morph males over a single heated perch, two perches at the same temperature, or two perches differing in temperature. Our first experiment revealed that orange-throated males are socially dominant. However, this hierarchy collapsed in our other experiments as yellow males became more aggressive. Interestingly, both males only ever secured their own perch where the perches differed in temperature. These findings mirror observations of morph behavioural flexibility in nature and studies of behaviour-environment interactions in non-polymorphic taxa. We conclude that colour morphs may have an underappreciated ability to assess resource-level changes and respond with concomitant flexibility in behaviour. [ABSTRACT FROM AUTHOR]

Behavioural syndrome literature suggests that behavioural traits may be coupled to form behavioural strategies that are consistent and repeatable across contexts. Typically these behavioural types are composed of bold, aggressive, dominant individuals and shy, less aggressive, subordinate individuals. Mountain chickadees living in varying climatic conditions across a montane environment appear to exhibit consistent behavioural types, such that high elevation birds, which experience harsher winter conditions and rely more heavily on spatial memory to retrieve food caches to survive winter, explore a novel environment at a slower rate (i.e., shy) and are socially subordinate to low elevation birds. Dominance is typically expressed in individual pairwise interactions, but it is not always clear which traits predispose an individual to become a dominant in such interactions. Aggression is frequently suggested to be associated with higher dominance status, yet the data are equivocal. Here we aimed to test whether previously described elevation related differences in social dominance might be associated with elevation related differences in aggression levels in mountain chickadees by using the mirror test. The mirror test can address potential differences in reactive and proactive aggression, although caution should be taken when using the mirror test as some species are able to self-recognize. Low elevation birds responded more aggressively to their mirror image than high elevation birds, suggesting that elevation related differences in aggression may be partially responsible for previously found differences in social dominance status. [ABSTRACT FROM AUTHOR]

The urination pattern of the Mozambique tilapia (Oreochromis mossambicus) depends on social context, and the olfactory potency of urine released depends on social rank (males) and repro-ductive status (females). This strongly suggests that urine mediates chemical communication in this species. The current study tested, firstly, whether urine production rate depends on sex or so-cial status and, secondly, whether differences in urination pattern and volume of urine stored are associated with variation in the morphology of the urinary bladder. Finally, the effect of urina-tion during aggressive male-male interactions was assessed. Urine production in catheterized fish depended neither on sex nor social status (males). Nevertheless, males had larger kidneys than fe-males. Dominant males had heavier urinary bladders than subordinate males or females, mainly due to enlarged muscle fibres, thicker urothelium and a thicker smooth muscle layer. In male pairs wherein urination was prevented by temporary constriction of the genital papillae, social interac-tion escalated to aggression (mouth-to-mouth fighting) more rapidly and frequently than control pairs. This was accompanied by elevated plasma testosterone and 11-ketotestosterone levels. In control encounters, the male that initiated the aggressive behaviour was usually the winner of the subsequent fight; this did not happen when the males could not urinate. These results suggest that the larger, more muscular bladder of dominant males is an adaptation, facilitating higher urination frequency, post-renal modulation and storage of larger urine volumes for longer. It is likely that uri-nary pheromones modulate aggression in male-male encounters by providing information on the social rank and/or motivation of the emitter; males are unlikely to invest in costly highly aggressive fights if they judge their opponent to be more dominant. Thus, a morphological explanation for the differing urination patterns of dominant and subordinant males, and females, has been provided, and a possible function for this behaviour in male-male interactions is suggested. [ABSTRACT FROM AUTHOR]

Results of experimental research are used to develop theoretical models of dominance hierarchy formation that incorporate effects of prior aggressive experience and body size. A combination of analytical models and computer simulations confirm previous theoretical treatments showing that intrinsic attributes such as body size fail to account for the degree of hierarchy linearity observed in nature for typical within-group variance of such attributes. Moreover, these models explain the mathematical dynamics of the operation of winner/loser effects during hierarchy formation. Additionally, I present an analysis of these models which shows that the degree to which relationships of component triads (all combinations of three individuals in a group) within a hierarchy develop sequentially can have a significant effect on linearity and is an emergent feature of prior experience effects that previously has not been examined. I explain how this feature can operate through physical and behavioral features of social groups that increase physical proximity of subgroups within a larger group, thus increasing the probability of sequential relationship development in component triads, which in turn provides the conditions for winner/loser effects to significantly increase the probability of component triad transitivity and hierarchy linearity. [ABSTRACT FROM AUTHOR]