Calf control by voice command in a Brazilian dairy

Brazilian dairymen present calves to their mothers at milking time as a stimulus for milk let-down. The calves fetched by calling them individually by name. Two crops of Gyr (Bos indicus) calves were observed experimentally. Their responses to the calls were consistent and statistically positive over both observations. Having strangers call the calves resulted in performance decrements, but positive responses still remained well above chance. Randomizing the calling orders had no deleterious effect. Positive responses and the number of calls necessary to elicit a positive response were independent, the latter being related to time of day and level of food deprivation. Calling the calves outside the milking context reduced positive responses dramatically, suggesting that the behavior was, in part, situation-specific. Cows solicit their calves through auditory signals “in nature”, and the husbandrymen's successful vocal control was probably derived from that preexisting ethological system.