The Good Trapping Company's Guide to Rat Behaviour:
Rat culture - Culture - the transmission of behaviour/information through generations and across social groups, via social learning and independent to genetics. See our Nature vs Nuture in rats page.
Rat behaviour is highly complex rather than simple reflexes.
Social learning - learning from others - is an integral part of their behaviour and consequently a major attribute to their success in allowing them adapt to multiple environments. This form of learning allows individuals to develop beneficial behaviour quickly with out costly trail and error or waiting for a genetic mutation to code for it.
Rats use social learning in a wide range of situations, but perhaps especially so in acquiring food preferences. Food preferences are socially transmitted between rats at points that are temporally and spatially distant from the food source, in a manner somewhat analogous to humans seeking restaurant recommendations from friends.
It is no coincidence that they have long whiskers and twitching noses, olfactory clues are critical to their learning from one another as to what to eat.
Olfactory clues come in different forms - Adult rats will scent mark trails to and from food sources, which are then preferentially followed by naive individuals. Olfactory clues on the whiskers and breath of one individual will influence the food preference of another- with environmentally naive rats showing strong preference for the olfactory clues of food on the breath/whiskers of environmentally experienced rats. The preference will stand across generations even when the original rats are not presents and regardless of the nutritional content of the food.
Learning what to eat even comes before birth: In utero, fetal rats detect odour-bearing particles that come from their mother's diet and cross the placental barrier. Shortly after birth, newborn rats respond positively to these foods. During nursing pups receive information about their mother's diet through her milk and subsequently prefer the foods she ate during lactation.
Rats also learn what not to eat, and this is where poison avoidance comes in: Rats are very neophobic when it comes to food: they tend to avoid new foods and have extremely sensitive learned food-aversions. If a rat does taste a new food it may try only a small amount the first time. If the food makes the rat feel ill, it scrupulously avoids that food in the future. This aversion is transmitted socially, for example in a classic experiment rats injected with a chemical causing nausea when either eating coca or cinnamon tasting food - will pass on their aversion to the food containing this chemical across generations and to peers. This aversion will continue even when the individual exposed to the nausea compound is not present or the chemical in the food.
Rats are not "born" with a knowledge of safe foods and poisons - but are fluid in their choice of cuisine adapting their pallet like a pirouetting ballerina - dancing to the song of good food.