دانلود رایگان مقاله تأثیر سن و محیط اجتماعی اولیه بر تمایل یادگیری اجتماعی گوپی

Social learning, learning from others, allows animals to quickly and adaptively adjust to changing environments, but only if social learning provides reliable, useful information in that environment. Early life conditions provide a potential cue to the reliability of social information later in life. Here, we addressed whether direct early life experience of the utility of social learning influences later social learning propensities. We reared guppy, Poecilia reticulata, fry for 45 days in three different social conditions which involved the presence of adult demonstrators providing cues about feeding locations in the tanks (‘follow adults’ and ‘avoid adults’ treatments), or their absence (‘no adults’ treatment). In the ‘follow adults’ treatment, juveniles that swam in the same direction as the adult demonstrators found food, whereas in the ‘avoid adults’ treatment, subjects that swam in the opposite direction to the demonstrators found food. We then tested the fish with a social learning task, to examine whether prior experience had influenced the social learning tendencies of the juveniles. After another 45 days of rearing under common-garden conditions with no adult fish present in the tanks, subjects were retested with the same social learning task, to investigate whether early experiences had effects persisting into adulthood. After 45 days of rearing we found no evidence for social learning in any of the experimental groups. However, after 90 days of rearing, we found evidence of social learning, but only in the ‘follow adults’ treatment. These results suggest that social learning propensities may develop over life, and that prior exposure to conspecifics providing useful foraging information during early life can shape the degree of reliance on social learning in adulthood.

DISCUSSION

We found no evidence for social learning after 45 days of experimental rearing. After 45 additional days of rearing in standard conditions, we found evidence for social learning on two behavioural measures, but only in those fish that had been exposed to demonstrators that reliably indicated food locations for the first 45 days of life. Our results are consistent with the ideas that performance on this social learning test is dependent upon age and that experience confined to early life affects social learning propensities in later life. The most striking aspect of our results is that early life experience had an effect 45 days later, after rearing in common-garden conditions. This suggests that early life had long-lasting effects that were not expressed until adulthood. We predicted, in contrast, that the strongest effects on social learning would be observed at 45 days and these effects would be potentially weakened after 45 days in common-garden conditions. Our results therefore suggest that social learning propensities may change over the lifetime of an individual. Similarly, a comparison of different ages of jack mackerel, Trachurus japonicus, revealed that social learning tendencies develop in older individuals, together with enhanced schooling behaviour (Takahashi, Masuda, & Yamashita, 2014). A number of explanations could account for the difference in social learning propensities with age that we observed. The social learning task may simply be too challenging or insufficiently motivating for younger fish. For example, younger fish, which are also smaller in body size, may be less motivated to visit locations where large fish were previously present, since larger guppies outcompete smaller guppies in competition for food and may be aggressive towards them (Chapman, Morrell, et al., 2008; Laland & Reader, 1999). Guppies were slower to enter either of the two feeding compartments on Day 45 than Day 90, supporting the idea they were less motivated by the task. Competition was also suggested to underlie age-dependent social learning in male skink lizards, Eulamprus quoyii: juveniles socially learned an association task but adults did not, potentially due to greater intermale competition among adults (Noble, Byrne, & Whiting, 2014). The relative age or size of demonstrators and observers has been investigated particularly in fish, and has been shown to influence who-learns-from-whom in both guppies and sticklebacks, Pungitius pungitius (Duffy, Pike, & Laland, 2009; Dugatkin & Godin, 1993; Vukomanovic & Rodd, 2007). Directed social learning (Coussi-Korbel & Fragaszy, 1995), in which socially acquired behaviours only flow through a subset of the population, may thus be very common.