Agonistic Behavior in Freshwater Crayfish The Influence of Intrinsic and Extrinsic Factors on Aggressive Encounters and Dominance

Fighting success and dominance in crayfish depends on a variety of extrinsic and intrinsic factors. Most intrinsic factors studied to date are related to the physical size of the crayfish. Larger crayfish or those with larger chelae often have advantages in agonistic interactions. Age, sex, and reproductive status can influence the physical size of the […]

Aggressive behaviors of the Japanese brown bear

Film analysis and direct observation suggest that 2 very different types of intraspecific fights occur among Japanese brown bears maintained in laige,stable colonies.Disputes arising over food are short, and involve such activities as threatening, muzzling,chasing, and flight. Weapon use during feeding fights primarily involves slashingblows to the back or head areas of the opponent. In […]

‘Roid rage in rats? Testosterone effects on aggressive motivation, impulsivity and tyrosine hydroxylase

Abstract In humans and animals, anabolic-androgenic steroids (AAS) increase aggression, but the underlying behavioral mechanisms are unclear. AAS may increase the motivation to fight. Alternatively, AAS may increase impulsive behavior, consistent with the popular image of ‘roid rage. To test this, adolescent male rats were treated chronically with testosterone (7.5 mg/kg) or vehicle and tested […]

Personality and predictability in fallow deer fighting behaviour: the relationship with mating success

Individuals often differ from each other in how they respond to environmental events: a feature of behaviour often termed animal personality. Furthermore, animals often show unpredictability in how much they respond to these events over time leading to the suggestion that personality and intraindividual variability (IIV) might have important fitness consequences. We investigated this hypothesis […]

Aggressive behaviour at regrouping is a poor predictor of chronic aggression in stable social groups

Commercial pigs globally are routinely mixed into new social groups. This results in regrouping aggression predominantly during the first 24 h which compromises welfare and productivity. Chronic aggression persists thereafter and is also undesirable. Management strategies are needed that reduce the costs of aggression in both of these contexts. Pigs vary greatly in aggressive behaviour […]