Laland, Kevin Neville; (1990) Social transmission in Norway rats and its implications for evolutionary theory. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis addresses the question of whether social transmission could play an evolutionary role by allowing learned behaviours to spread through animal populations, changing their selection pressures and resulting in a significant genetic response. The answer to this question hangs critically on the nature and stability of social transmission, and consequently this was the focus of the empirical component of the thesis. Laboratory studies of social learning and social transmission in Norway rats were conducted employing two empirical paradigms: (a) the transmission of foraging information amongst animals digging for buried food; and (b) the transmission of food preferences by excretory marking of food sites. Simple experiments were conducted first to establish whether social learning was taking place, and to investigate the learning mechanism. Secondly, transmission studies investigated the passage of foraging information or food preferences along chains of animals. The foraging for buried food experiments established that the foraging efficiency of naive animals could be enhanced by social learning, and this elevation in performance could be transmitted along chains of animals. The food site marking experiments found that rats can mark food sites with their excretory products, rendering those sites more attractive to conspecifics than unmarked sites, and resulting in the communication and social learning of food preferences. Transmission studies found that enhanced levels of consumption of particular diets could be transmitted along chains of animals. Both sets of experiments identified factors which affect the stability of socially transmitted traits. A second, theoretical component to the thesis employed simple mathematical models to investigate the interaction between "memes" and genes in evolution. This exercise allowed an assessment of three hypotheses concerned with the role of social transmission in evolution. The relevance of the empirical and theoretical findings are discussed, and suggestions made for further research.

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