To check this out, I spent(ใช้จนหมด) hours(ชั่วโมง) at the Oakland Zoo(สวนสัตว์), often surrounded(ล้อมรอบ) by school kids(เด็ก) on field trips(การเดินทาง), to observe the different animals(สัตว์)," said(กล่าว) Banks. "Sure enough, when goats, antelope and other grazing prey animals put their head(หัว) down to eat(กิน), their eyes rotated to maintain the pupils' horizontal alignment(การจัดตำแหน่ง) with the ground(พื้นดิน).