CONFLICT AND COOPERATION - SOCIOBIOLOGICAL PRINCIPLES AND THE BEHAVIOR OF PIGS

The pig provides many examples of how principles of behavioural ecolog y and sociobiology can lead to insights into farm animal behaviour. Ac cording to parent-offspring conflict theory, parents should tend to gi ve a level of parental investment somewhat below that solicited by the young. When closely confined during lactation, sows can do little to limit the amount of contact with the piglets, and the young stimulate a prolonged, high level of lactation. Certain alternative housing syst ems allow the sow to limit the stimulation she receives, and the resul ting reduction in lactation can actually be advantageous to both parti es. Communal care of offspring has both advantages and disadvantages i n various species; these may help to explain why communal care occurs to a limited extent in pigs, and why sows isolate their litters in ear ly lactation. Neonatal competition and mortality among newborn piglets have strong parallels in the ''facultative siblicide'' which adjusts brood size in numerous species of birds. These species typically produ ce slightly more young than are normally raised, and the number of sib lings that survive is determined by the ability of the smaller young t o withstand intense competition. The hypothesis that pigs have evolved a similar system of brood reduction may explain why piglet mortality is such an enduring problem and requires solutions different from thos e that work for other domestic species. Resource defence theory provid es a functional framework for studies of aggressive behaviour. Factors determining the defensibility of a resource include its degree of clu mping in time and space, and these suggest ways to reduce competition for food and other resources. However, aggression involved in establis hing social dominance is more likely to be influenced by manipulating traits of the competing animals (competitive ability, familiarity) rat her than the defensibility of resources, We conclude that principles o f behavioural ecology and sociobiology provide a useful functional and evolutionary perspective to complement other approaches to the study of farm animal behaviour.