Promoting contest skill to reduce the welfare costs of animal agonistic interactions

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SummaryAggression is a major and routine challenge to welfare in many species of managed animals despite decades of research aimed at minimising it. Aggression also affects health, survival and fitness in wild populations. Aggressive contests accrue physical (e.g. injuries), emotional and energetic costs. Individuals vary greatly in the costs paid during aggressive contests, irrespective of whether they win or lose. Some individuals can resolve contests quickly with minimal costs. The mechanism by which they achieve this is unknown and, until we understand it, reducing the welfare penalty of aggression will be difficult. Our aims are to determine a) whether skill facilitates contest resolution and thus reduces contest costs, and (b), if so, whether husbandry practices can be manipulated to promote skilful fighting, reduce contest costs and enhance welfare and production in a commercial setting. The project uses pigs as they offer an ideal model system and because most of the one billion pigs slaughtered annually experience significant aggression. One large experiment will address all objectives below:1. Characterise and quantify skill in contest aggression and defence2. Determine the effect of the social developmental environment and contest experience on skill3. Assess the contribution of socio-cognitive ability and assessment strategy to skill4. Quantify the relationship between skill and conventional measures of fighting ability and aggressiveness5. Determine whether contest skill reduces the welfare costs of aggression in a commercially realistic scenarioContests demand the use of complex behaviours. Skill is influential in human sporting contests, yet remarkably its role in animal aggressive contests is almost entirely unstudied. A recent framework has proposed that contest skill comprises efficient, accurate, precise and appropriate behavioural execution. We will test this framework and quantify skill by its effects on contest success and costs (Obj. 1). Variation in commercially relevant early-life opportunities for play fighting experience and minimally-damaging contest experience will test their effects on later contest skill (Obj. 2). Behaviour must be underpinned by rapid and well-informed decisions, which requires that animals assimilate and process complex information and turn it into knowledge (termed cognitive ability). Whether cognitive ability improves the behavioural execution of skill is unknown. A specific cognitive challenge during contests is to gather information and use this to decide when to give up. Several classes of information-gathering model have been developed. In the simplest, termed self assessment, animals make fight decisions based purely on their own fighting ability and stamina, without reference to the ability of an opponent. After a threshold amount of energy has been spent on fighting, the individual will give up. In a second class, termed mutual assessment, animals self assess but also assess the fighting ability of an opponent. Although more complex, it allows an animal to quickly withdraw from a fight it is likely to lose and substantially reduces the costs paid. Hence, Obj. 3 will test whether cognitive ability and individual use of assessment strategy promote skill as reflected in appropriate and efficient behaviour. In doing so we provide the first quantification of assessment strategies at the individual animal level. Obj. 4 will also quantify whether superiority in other determinants of fighting ability (e.g. weight) and an aggressive personality enhance or suppress skill. Crucially the project also has applied relevance. Obj. 2 will inform how management can promote skill in dyadic contests. Importantly, in Obj. 5 pigs will be regrouped in a commercially-realistic way (groups of 12 animals) to test whether skill in paired contests improves welfare in a real-world scenario.