Krijgsveld K L, Visser G H, Daan S
Zoological Laboratory, University of Groningen, PO Box 14, 9750 AA, Haren, Netherlands.
Physiol Behav. 2003 Jul;79(2):311-9. doi: 10.1016/s0031-9384(03)00117-3.
We examined whether low ambient temperatures influence foraging behavior of precocial Japanese quail chicks and alter the balance between investment in growth and thermogenic function. To test this, one group of chicks was exposed to 7 degrees C and one group to 24 degrees C during foraging throughout the developmental stage. Chicks adapted well to the temperatures through a high flexibility in behavior and physiological development. In response to cold, chicks shortened foraging bout lengths two- to sixfold, and increased cycle lengths (i.e. length of a brooding bout plus subsequent foraging bout), resulting in a decrease in total foraging time. Body temperature during foraging was lower in cold-exposed chicks but did not drop below 37.8 degrees C, suggesting that the direct cause to end a foraging bout was not body temperature. The metabolic rate of cold-exposed chicks was reduced by 48% to 60% when switching from foraging to brooding, which may be an important factor in determining foraging behavior of precocial chicks. Mass-specific food intake of the cold-exposed chicks exceeded that of warm chicks by 15%. Cold-exposed chicks doubled foraging efficiency to reach this intake during their reduced foraging time. Metabolic rates initially were similar in both groups, but increased rapidly and were elevated in cold-exposed chicks from 15 days of age onward. Growth rate initially was reduced in cold-exposed chicks, and exceeded growth of warm chicks only after 21 days of age. These results suggest that in response to cold, a shift occurs in the balance between growth rate and thermoregulatory function in favor of thermoregulatory function.
我们研究了环境低温是否会影响早成性日本鹌鹑雏鸟的觅食行为，并改变其在生长投入和产热功能之间的平衡。为了验证这一点，在整个发育阶段的觅食过程中，将一组雏鸟暴露于7摄氏度环境，另一组暴露于24摄氏度环境。雏鸟通过行为和生理发育的高度灵活性很好地适应了这些温度。面对寒冷，雏鸟将觅食回合时长缩短了2至6倍，并增加了周期长度（即一次育雏回合加上随后的觅食回合的长度），导致总觅食时间减少。暴露于寒冷环境中的雏鸟在觅食时的体温较低，但未降至37.8摄氏度以下，这表明结束一次觅食回合的直接原因不是体温。从觅食转换到育雏时，暴露于寒冷环境中的雏鸟的代谢率降低了48%至60%，这可能是决定早成性雏鸟觅食行为 的一个重要因素。暴露于寒冷环境中的雏鸟的单位体重食物摄入量比处于温暖环境中的雏鸟高出15%。暴露于寒冷环境中的雏鸟在觅食时间减少的情况下，将觅食效率提高了一倍以达到这一摄入量。两组雏鸟最初的代谢率相似，但从15日龄起，暴露于寒冷环境中的雏鸟的代谢率迅速上升并保持在较高水平。暴露于寒冷环境中的雏鸟的生长率最初有所下降，仅在21日龄后才超过处于温暖环境中的雏鸟的生长率。这些结果表明，面对寒冷时，生长率和体温调节功能之间的平衡发生了变化，有利于体温调节功能。
