導入牛と古参牛との社会行動の経日的変化

抄録

Five heifers aged 2 years old were individually introduced to a herd of 16-18 Japanese Black cows aged 3 to 10 years old. Each of the five heifers was individually observed 1 hour at the introduction day, 6 hours at the next day and 6 hours every 15 days until 3 months after the introduction. Their social behaviour was investigated using the focal-animal sampling method and scored of each of 23 behaviour categories.Investigative behaviour, aggressive behaviour, fighting and mock-fighting occurred frequently at 1 hour of the introduction. In the introduction day, the threat display as the fight-or-flight posture and pawing and the flehmen occurred frequently in original group cows and escape behaviour in the introduced heifers occurred few. Social behaviour in the next day was not different qualitatively from that in the introduction day, but quantitatively social behaviour was suppressed largely. The total frequency of social behaviour changed little after 15 days of the introduction, then the lowest was around 45 days of the introduction. Social behaviour varied widely with the individual and the social individuality of heifers was explained by three principal components, that is aggressiveness, affiliativeness and strangeness. Escape behaviour has disappeared until 45-60 days after the introduction and after that mock-fighting, fighting and affiliative behaviour emerged again in heifers which showed less frequently escape behaviour.Escape behaviour has not disappeared and fighting did not emerge again in heifers which showed more frequently escape behaviour. Heifers which have the character of affiliativeness, adopted again mock-fighting and affiliative behaviour 45-60 days after the entry. The individual variation in the frequency of receiving social behaviour from original cows is a little. So familialization of strange heifers and original cows may mainly depend on the action from strange heifers. From above results, we thought that the strangeness of each other faded until 45-75 days after the introduction, the introduced heifers were neglected from original cows and neglected original cows, and after that heifers gradually positively took part in a group.