A note on the effect of number (single or twin) and sex of contemporary siblings on male-like play behavior of lambs (Ovis aries)

This study evaluates the effect of the number and sex of contemporary siblings on male-like play behavior of Suffolk lambs (Ovis aries). Fourteen males and 14 females, all single born, plus 26 ram lambs born co-twin to another male (n = 14) or female (n = 12) as well as 26 ewe lambs born co-twin to another male (n = 12) or female (n = 14) were observed daily for 7 weeks from 1 week of age. Two observers sitting outside a sand-bedded pen (10 × 5 m) recorded received and performed behavior (butts, nudging, attempts to mount, and mounts) by the lambs in the pen from 08:00 to 09:00 and 16:00 to 17:00 hours. Animals were in the pen only during the observation periods; the rest of the day they remained with their mothers in individual pens. Male-like play behavior patterns were displayed by both male and female lambs. Males were more active (P < 0.05) than females. Butting was the most frequent activity and performed mostly by ram lambs, recipients were generally males, and most resulted in reciprocal simultaneous encounters (sparring). Single males performed most of the nudging activity, which was the least frequent of the observed behaviors. Males with twin brothers mounted significantly (P < 0.05) more than males with twin sisters, and females with twin sisters performed the lowest amount of gutting and nudging. Lower (P < 0.05) levels of activity were found during the first 2 weeks. Overall, it was concluded that male lambs performed and received more male-like play behaviors than female lambs and the influence of sex of contemporary sibling was restricted to some behaviors: butting and nudging in females and mounting in males.