Bilcik B, Keeling L J, Newberry R C
Slovak Academy of Sciences, Institute of Animal Biochemistry and Genetics, 900 28 Ivanka pri Dunaji, Slovakia.
Swedish University of Agricultural Sciences, Department of Animal Environment and Health, P.O. Box 234, 532 23 Skara, Sweden.
Behav Processes. 1998 Apr;43(1):53-9. doi: 10.1016/s0376-6357(97)00081-8.
It has been shown that duration of tonic immobility (TI) reflects predation risk and levels of fearfulness. Since the chances of escaping predation are higher in larger groups, birds from these groups should have shorter TI duration. On the other hand, increased competition between birds in larger groups might lead to greater fearfulness and longer TI in larger groups. The aim of this study was to test these two hypotheses. Laying hens raised in floor pens in group sizes of 15, 30, 60 and 120, each with four replicates, were used. Tonic immobility tests were performed on adult birds, either directly 'in' their home pen or 'out' in a separate room. In the test 'in', duration of TI increased with group size, with a significant difference between group sizes 15 and 120 (P=0.012). In the test performed 'out', there was a trend for TI to be longer in larger groups. The duration of TI in groups tested 'in', was significantly shorter than in groups tested 'out' (P<0.00l). The results of this study suggest that although the ultimate function of TI is to reduce predation, the social environment is a proximate factor affecting TI duration in domestic hens.
已表明强直静止（TI）的持续时间反映了捕食风险和恐惧程度。由于在较大群体中逃脱捕食的机会更高，来自这些群体的鸟类的TI持续时间应该更短。另一方面，较大群体中鸟类之间竞争的增加可能导致更大的恐惧以及较大群体中更长的TI。本研究的目的是检验这两种假设。使用在地面围栏中以15、30、60和120只的群体规模饲养的蛋鸡，每个规模有四个重复。对成年鸟类进行强直静止测试，要么直接在它们的家围栏“内”进行，要么在单独的房间“外”进行。在“内”测试中，TI的持续时间随群体规模增加，群体规模15和120之间存在显著差异（P = 0.012）。在“外”进行的测试中，较大群体中TI有更长的趋势。在“内”测试的群体中TI的持续时间明显短于在“外”测试的群体（P < 0.001）。本研究结果表明，虽然TI的最终功能是减少捕食，但社会环境是影响家鸡TI持续时间的一个近因。
