Dietary conservatism is a foraging strategy in which individuals show a prolonged reluctance to eat novel foods, even after neophobia has been overcome. Within any given population of foragers, some will exhibit DC and some will exhibit adventurous consumption, an alternative strategy in which individuals readily accept novel food immediately after neophobia has waned. It is important to emphasise that DC and neophobia are distinct processes distinguished by the persistence of an individual’s reluctance to eat over repeated encounters with novel food and over long time periods.
Background
Animals are often faced with a choice between eating familiar food or expanding their diet by consuming a novel item. It has long been recognised that animals hesitate to approach novel foods they encounter and this initial fear of novelty lasts only a matter of minutes in most animals. By contrast, a second response to novel food has been identified, in which, after the foragers have overcome their neophobia to approach and made contact with novel food, they continue to avoid eating it for considerable periods of time. This much longer avoidance of novel food is called “Dietary Conservatism” and has been shown to have a genetic basis. Unlike neophobia, DC does not rapidly subside over repeated encounters. For example, Kelly found that among wild birds, some individuals avoided novel food for more than 2 years and 200 exposures, even though the novel food was conspicuous and fully palatable.
One observation about the phenomenon of DC is that each of the forager populations examined so far has included some individuals that are consistently conservative. However, the rest of the population exhibit a clearly different response to foraging encounters with novel foods. “Adventurous consumers” eat novel food as soon as they encounter it, or after their neophobia has waned enough for them to approach and touch it. In all vertebrate populations tested so far, both AC and DC strategies have been represented by a sizable proportion of the population.
Plasticity in expression of DC
Although DC is a trait with a genetic basis, its expression is, like any behaviour, a dynamic interaction between genes and the environment. Specifically, the expression of DC has been shown to be influenced by an individual’s experience of the encounter with novel food in different contexts. For example, extended experience with multiple different colours of novel food makes a DC individual more likely to accept an additional novel colour. Conversely, encounters with novel food which is distasteful, increases the strength of the DC response, making the individual extremely averse to novel foods thereafter. Social cues can also be important. If a domestic chick observes another individual consuming novel food, then the avoidance of novel food by the observer is reduced. Alternatively, if chicks cannot see the food choice, and their companion is simply a competitor for food, then DC individuals become more DC and only take the familiar food. The strength of expression of DC also depends on the forager’s perceived risk of predation pressure, hunger levels, and perceived availability of food.
Maintenance of DC and AC foraging strategies
It is possible that the balance of DC and AC foraging strategies in a population is influenced by the forager’s ecology. For example, DC may be favoured in habitats where prey are relatively cryptic, since it allows the predator to specialise on a single prey type. In this way DC individuals could benefit from the use of a ‘search image’ for that prey type and the accumulation of experience of handling that prey. In addition, where there are many toxic prey types, DC foragers may be favoured as they are less likely to be poisoned if they eat only nontoxic prey, with which they are already familiar. By contrast, AC foragers may be favoured in environments with a high diversity of prey, but a low abundance of individual prey types. In such an environment, AC predators would more quickly discover which of the available range of prey are edible and would then be able to exploit all of those prey types, rather than a familiar, but smaller, subset.
