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When optimal foraging theory emerged in 1966, it was highly controversial and stayed that way for years. Many criticisms of the theory centered on use of the word “optimal”. Opponents of the theory claimed that as a result of trade offs in natural selection, behavior can never truly be optimal (Gould, 1979). Others asserted that optimal behavior would require animals to achieve a high level of intelligence to determine the consequences of their foraging actions (Stephens et al., 2007). Early on, the most damaging criticisms were that optimal foraging theory either had not been tested sufficiently, or that it had been tested and failed (Perry and Pianka, 1997).
Proponents of optimal foraging theory responded in several ways. When the theory was most controversial, researchers continued studying it but did not use the word “optimal” in their work (Perry and Pianka, 1997). Stephens et al. explain that an animal does not need to understand its own foraging behavior for it to be optimal, just as a baseball player does not have to understand physics (2007). Most importantly, numerous studies, including some mentioned in this chapter, have upheld the predictions of optimal foraging theory.
Humans domesticated pigs over 8,000 years ago (Mignon-Grasteau et al., 2005). Although the domestic pig and its ancestor the wild boar are vastly different in appearance ( [link] and [link] ), few behavioral differences between the subspecies have been found (Gustafsson, 1999b). For more about domestication, see [link] .
Gustafsson et al. examined foraging differences between domestic pigs and crossbred pigs, which had one domestic parent and one wild parent. The pigs foraged in a maze containing buckets with a limited amount of food to model gradually depleting patches. In some conditions, the researchers put barriers between patches in order to induce a cost of moving from one patch to another. They made three predictions based on optimal foraging theory: that pigs would adjust their foraging strategy as food in a patch was depleted by spending less time in that patch; that pigs would spend more time in each patch when there was a cost associated with moving between patches, and that wild boar hybrids would move between patches more frequently and spend less time in each patch, using a costlier strategy. (Gustafsson, 1999a)
Bottom: A female wild boar and her piglets. Creative Commons- Licensed
<http://www.flickr.com/photos/j-pocztarski/3456321271>
Each prediction is based on the main tenet of optimal foraging theory: that animals minimize costs and maximize food intake while foraging. Domestic pigs were expected to use a less costly strategy because through the process of domestication, costly strategies are selected against (Jensen and Gustafsson, 1997). A costly strategy that involves moving frequently between patches may be beneficial in the wild because it reduces the chance of being caught by predators. Under the protection of humans, this strategy would not be advantageous because it would cause the pigs to expend energy moving when they were not in danger of being caught by predators.
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