Krebs investigated experimental plots in Canada's Yukon territory that contained hare populations.
克雷布斯调查了加拿大育空地区含有野兔种群的试验田。
2
Krebs has discovered that great blue herons look up more often when in smaller flocks than when in larger ones, solely as a consequence of poor feeding conditions.
克雷布斯发现，大蓝鹭在较小的群体中比在较大的群体中更容易抬头，这完全是由于恶劣的饲养条件造成的。
3
Krebs hypothesizes that the herons in smaller flocks are watching for herons that they might follow to better feeding pools, which usually attract larger numbers of the birds.