[Imprinting of domestic animals on man]

Male farm animals (kids, lambs and piglets) were kept isolated from conspecifics for their first 10 days of life. Until reaching sexual maturity they lived like pets in close contact with human beings; later some of them were removed to farms. Here they could interact with animals of other species, but not with conspecifics. Their first contact with conspecifics took place after they were sexually mature. In simultaneous choice experiments, offering a conspecific and a human being as passive participants, the animals were tested for any imprinted preference for human beings. Criteria were sexual advances and copulation attempts, as these indicate a strong social attachment. Two conditions proved necessary for imprinting on another species: 1. long-term isolation from conspecifics, and 2. close contact with another species during this time. Under these circumstances the term "sensitive period" may not be appropriate. Contrary to imprinting in birds isolation during the first days of life is not necessary for imprinting on another species to take place.