They might be partridge chicks and she might be a duck, but there is no doubt about it - she is mum. And they will faithfully follow her, safe in the knowledge that she will provide the warmth, food and protection they expect from a caring parent.

When the chicks were found, abandoned by their absent mother, they were dying. So they were passed into the care of a duck called Fluffy. Despite the species gap, the chicks quickly decided Fluffy was their mother and have never looked back.

It is all down to a pattern of behaviour called “imprinting”, a term coined by the Austrian zoologist Konrad Lorenz (1903-1989). As a young boy, Lorenz was given a duckling by a neighbour who had noticed his enthusiasm for nature. To the child’s delight, the day-old bird took to following him wherever he went. That moment made a lasting impression on Lorenz, who studied that particular animal’s behaviour and ultimately won a Nobel Prize for his work.

Several decades after the duckling, Lorenz was being followed around by newly hatched goslings that had also “imprinted” on him. He found there is a genetically critical period during the infancy of many birds and mammals in which they imprint on the first likely animal they see. Usually this is the mother, but occasionally a substitute such as a wide-eyed child, a duck called Fluffy or even, in some laboratory tests, an appropriately shaped piece of wood, will do. What is more, the process is irreversible. Once the image is seared into the neural circuits of the infant, it cannot be purged or replaced. Those partridge chicks could be reintroduced to their biological mother bt would still hunt for the reassuring figure of Fluffy.

Lorenz deduced that this behaviour was rather useful. New-born animals are extremely dependent on parental support in a world in which many other animals view them as convenient snacks. Those babies whose brains are hard-wired to give them a natural urge to stick close to a responsible adult are less likely to wind up as fast food for a predator. Indeed, the colder, hungrier or more frightened an infant becomes, the stronger its instinct to follow mum.

Imprinting is not limited to parental bonding. Some species of bird only learn the songs they will later sing in adulthood during a critical period of their infancy. Biologists have listened in astonishment as 12-day-old nightingale chicks that have spent a single week with a singing black-capped warbler go on, the following spring, to sing only typical black-capped warbler songs.

Humans are no exception. Any scientist who attempted to test the veracity of such legends as Tarzan, who was brought up by apes, or Romulus and Remus, who were nurtured by a she-wolf, would receive a prison sentence rather than a Nobel Prize. Yet a human infant undergoes imprinted learning, from responding to its mother’s voice to grasping the basic sounds of its mother tongue.

STEVE FARRAR

Weblinks

Articles on imprinting: http:britannica.combcomeb article?mid=1173626

Konrad Lorenz: http:www.nobel.semedicinelaureates1973lorenz-autobio.html

Royal Society for the Protection of Birds education resources: http:www.rspb.org.ukeducationdefault.htm

Steve Farrar is science correspondent for The Times Higher Education Supplement