Diffusion of foraging innovations in the guppy.

The way in which novel learned behaviour patterns spread through animal populations remains poorly understood, despite extensive field research and the recognition that such processes play an important role in the behavioural development, social interactions and evolution of many animal species. We conducted a series of controlled diffusions of foraging information in replicate experimental populations of the guppy, Poecilia reticulata. We presented novel foraging tasks over 15 trials to mixed-sex groups, made up of food-deprived and nonfood-deprived adults (experiment 1) or small, young fish and old, large adults (experiment 2). In these diffusions, knowledge of a route to a feeder could spread through the group by subjects learning from others, discovering the route for themselves, or, most likely, by some combination of these social and asocial learning processes. We found a striking sex difference, with novel foraging information spreading at a significantly faster rate through subgroups of females than of males. Females both discovered the goal and learned the route more quickly than males. Food-deprived individuals were faster at completing the tasks over the 15 trials than nonfood-deprived guppies, and there was a significant interaction between sex and size, with a sex difference in adults but not young individuals. There was also an interaction between sex and hunger level, with food deprivation having a stronger effect on male than female performance. We suggest that information may diffuse in a similar nonrandom or 'directed' manner through many natural populations of animals. Copyright 2000 The Association for the Study of Animal Behaviour.

Foraging innovation in the guppy.

When novel behaviour patterns spread through animal populations, typically one animal will initiate the diffusion. It is not known whether such 'innovators' are particularly creative individuals, individuals exposed to the appropriate environmental contingencies, or individuals in a particular motivational state. We describe three experiments that investigated the factors influencing foraging innovation in the guppy Poecilia reticulata. We exposed small laboratory populations of fish to novel foraging tasks, which involved exploration and problem solving to locate a novel food source. Experiments 1 and 2 found that (1) females were more likely to innovate than males, (2) food-deprived fish were more likely to innovate than nonfood-deprived subjects, and (3) smaller fish were more likely to innovate than larger fish. We suggest that the sex difference may reflect parental investment asymmetries in males and females. Experiment 3 found that past innovators were more likely to innovate than past noninnovators. Collectively, the results suggest that differences in foraging innovation in guppies are best accounted for by differences in motivational state, but, in addition, guppies may vary in their predisposition to innovate. Copyright 1999 The Association for the Study of Animal Behaviour.

Who follows whom? Shoaling preferences and social learning of foraging information in guppies.

Preferences of fish for different types of shoals may influence the transmission of novel information through them. We investigated the factors influencing the preferences of guppies, Poecilia reticulata, for different shoals in order to shed some light on how information transmission occurs. Adult subjects were given a choice between swimming with two diverging shoals of conspecifics that differed with respect to key characteristics. In six choice experiments, subjects discriminated between shoal partners on the basis of: (1) shoal size, subjects preferring a shoal of 10 to a single fish; (2) size of shoaling fish, small fish preferring small conspecifics rather than an equal number of large fish, while large fish showed no preference; (3) local foraging experience of shoaling fish, shoals containing fish that had previously been repeatedly fed in the experimental tank being preferred to shoals with no such experience; and (4) familiarity of shoaling fish, guppies preferring familiar rather than unfamiliar conspecifics. No discrimination on the basis of colour or hunger was observed. In addition, following a shoal to a food site on just three trials allowed guppies to learn a route, or food site, preference. Guppies were considerably more likely to learn to adopt the behaviour shown by members of a shoal of several demonstrators than an alternative behaviour shown by a single conspecific demonstrator. The relationship between preferences for different shoals and the social transmission of information is discussed in the light of these findings. The results suggest that shoaling preferences may strongly influence the social transmission of novel foraging information or feeding preferences through fish populations, and imply that learned infor-mation may diffuse through fish populations in a nonrandom, or directed, manner. Copyright 1998 The Association for the Study of Animal Behaviour.

Shoaling generates social learning of foraging information in guppies

Two experimental studies are reported which investigate the social learning of foraging information in guppies, Poecilia reticulataIn both cases, untrained adult female guppies swam with trained conspecifics to feed, and in the process learned a route to a food source. In experiment 1, subjects were given 5 days experience swimming with demonstrator fish trained to take one of two equivalent routes to food. When tested alone, subjects preferentially used the route of their demonstrators. Experiment 2 investigated whether this social learning could mediate the stable transmission of route preferences among small populations of fish. This experiment used a transmission chain design, in which fish in small founder populations were trained to take one of the two routes, with founder members gradually replaced by untrained conspecifics. Three days after all founder members had been removed, populations of untrained fish still maintained strong preferences for the routes of their founders. The results suggest that the tendency to shoal may facilitate a simple form of guided social learning, which allows guppies to learn about their local environments. They also imply that selectively neutral behavioural alternatives may be maintained as traditions in aggregated animal populations by very simple social mechanisms. The transmission chain method may be particularly useful for studying social species, such as the guppy, that do not respond well to isolation testing.