UC Davis

Consistent individual behavioral differences (CIDs) are evident in breeding ewe populations and may carry fitness consequences that affect lamb outcome, especially in extensive settings that involve minimal human intervention. These CIDs are described as co-varying behavioral and physiological response patterns to challenge, that may be elicited during human-animal interactions. The aims of this dissertation were to assess CIDs during human animal interactions (HAIs) in restrained and unrestrained contexts when the lamb was not present (Chapter 2); assess CIDs among ewes during and after lamb processing in relation to indicators of lamb outcome including birth weight, growth rate and weaning weights (Chapter 3); and evaluate the relationship between CIDs when the lamb is and is not present during pre- and postnatal HAIs with inclusion of indicators of lamb outcome (Chapter 4). Using practical, on-farm methods to evaluate CIDs among ewes, Chapter 1 revealed no evidence for a stable behavioral trait (two or more co-varying behaviors) in the presence of a human, however, there was evidence for repeatability in singular behaviors including duration of ‘head down’ while ewes were being directly handled and frequency of ‘environmental vigilance’ when in the presence of a human. Previous research suggests a personality trait related to the presence of a human may be activated during lamb processing that is an unreliable indicator of adaptive maternal care. A unique behavioral response characterized by pacing, avoiding the human and restricted grazing was elicited during lamb processing and was unrelated to indicators of lamb outcome and adaptive maternal care (Chapter 3). Proximity maintained from the human during lamb processing (similar to maternal behavior scores, O’Connor et al. (1985) was inconsistent between years and seemingly a reflection of maternal investment which may be influenced by lamb weight. Finally, patterns of behavior were identified between periods when the lamb was and was not present (Chapter 4). Duration of ‘head down’ when the ewe is being handled by the human was related to frequency of ‘open-mouth vocalizing’ after lamb processing, when the ewe and lamb were alone together and positively related to lamb birth weights. Few studies have explored the relevance of head postures in sheep, however, ‘head down’ behavior is thought to be indicative of stress and negative arousal and should be considered as a potentially, biologically important behavior in sheep, worth consideration into selective breeding programs.