Negative play contagion in calves

Play can spread contagiously between individuals and has been proposed as a way for high-playing animals to ‘seed’ positive affect in group-mates. We quantified the strength and direction of play contagion in dairy calves by manipulating play via milk allowances. Calves were housed in uniform groups all receiving high (UHigh) or low (ULow) milk, or in mixed groups with two high-milk (MHigh) and one low-milk (MLow) calf per group. Locomotor play was recorded with leg-mounted accelerometers on two consecutive days when calves were four and eight weeks old. We expected elevated play in MLow compared with ULow if positive contagion was strong. Contrary to expectations, spontaneous play was suppressed in MHigh calves compared to UHigh, while MLow did not exceed ULow. These findings provide the first quantification of a negative play contagion effect under prolonged social contact, suggesting negative contagion may more strongly influence play than positive contagion.