PubMed · 15193193
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Heather Wood. 2004. Commentary: threading some beads.. https://doi.org/10.1348/147608304323112492
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Game theory models of animal contests make many non-mutually exclusive predictions, complicating empirical tests. These predictions regard the relationship between contest parameters and fighting ability, for which body size is usually used as a proxy. However, in many systems, body size may be a limited proxy since multiple traits and contextual factors such as experience influence fighting ability. Using contests between male Cape dwarf chameleons, Bradypodion pumilum, I test alternative game theory models of extended contests. I show how the most likely candidate model can be identified through a process of elimination, based on tests of key predictions. In addition, I present a measure of fighting ability based on multiple traits that allows ability to change as experience changes. In dwarf chameleons, persistence is based on loser thresholds rather than assessment of relative ability, ruling out the sequential assessment model. Winners and losers do not match behaviours in early parts of the contest, arguing against all types of war of attrition models. Although the cumulative assessment model remained as the most likely candidate model, not all specific predictions of this model were upheld.
Substance P and its NK-1 receptor are involved in the modulation of aggressive behavior. Because of the role of the basolateral nuclear group (BNG) of the amygdala in canine aggression, neurokinin-1 receptor (NK-1) immunoreactivity in this brain region was assessed stereologically in 7 normally behaving and 6 pathologically aggressive dogs. The first aim of this study was to obtain information about the absolute number of neurons expressing the NK-1 receptor in the canine BNG because absolute numbers of neurons expressing the NK-1 receptor are not documented in literature. Additionally, an exploratory comparison was made between NK-1 expressing neurons in the BNGs of normally behaving and aggressive dogs. Results showed a very low amount (1-2%) of BNG neurons containing the NK-1 receptor in both groups. Aggressive dogs had significantly more NK-1-receptor-positive BNG neurons than normal dogs, but the numerical densities and fractions of receptor-positive neurons did not differ significantly between both groups. Combined with the fact that aggressive dogs have 27% more neurons in their BNGs than normal dogs, as reported in a previous study, these findings suggest a limited role for the NK-1-receptor-positive neurons within the BNG in the modulation of canine aggression. The present report of absolute numbers of neurons expressing the NK-1 receptor in the canine BNG could however be useful for further quantitative studies.
Steroid hormones play an important role in modulating social behavior in many species. Estrogens are thought to act on an interconnected network of hypothalamic and limbic brain areas to affect aggressive behavior, although the specific nuclei unknown remain unspecified. We show that individual variation in estrogen receptor alpha (ERalpha) immunoreactivity in the lateral septum (LS), ventral bed nucleus of the stria terminalis (vBNST), and anterior hypothalamus (AHA) of CD-1 mice is positively correlated with aggressive behavior. When males were treated with fadrozole (an aromatase inhibitor), aggressive behavior was reduced, although castration did not reduce aggression. These results suggest that estrogens modulate aggressive behavior by acting on a circuit that includes the LS, vBNST, and AHA and that the source of estrogens is non-gonadal. Fadrozole also decreased c-fos expression in the lateral septum following aggressive encounters. Although the effects of estrogen on aggression appear to involve regulation of neuronal activity in the LS, additional processes are likely involved. These results suggest that estrogen acts in a specific subset of a complex network of nuclei to affect aggressive behavior.