Temporal association between food distribution and human caregiver presence and the development of affinity to humans in lambs

The presence of the caregiver around feeding favors the development of a human-animal relationship. To understand the underlying mechanism, we tested various temporal associations between food distribution and human presence: from an early age, a person was repeatedly present for 2 min just before milk distribution ("Forward"), during milk distribution ("Simultaneous"), and 20 min afterwards ("Delayed"). The "Control" group received no human contacts. During the treatments, "Forward" and "Delayed" lambs had more physical contacts with the person than "Simultaneous" lambs. When tested in unfamiliar environments, they stood longer near the person than did "Control" or "Simultaneous" lambs, which did not differ. Only "Forward" and "Delayed" lambs bleated when separated from the person. Fasting before testing had no effect. "Forward" and "Delayed" seemed to produce the same human-animal relationship, showing that this did not rely only on a conditioning process associating the caregiver with food. The caregiver may acquire properties for social support through other mechanisms (attachment and/or postingestive effects).