70 million years ago,Albertosaurus was the most fearsome hunter in North America.
七千万年前，阿尔伯特龙是北美洲最可怕的猎手。
It was one of the few dinosaurs that would take on the horned Arctic dinosaur.
它是少数敢于攻击带角的北极恐龙的恐龙之一。
This herd of Pachyrhinosaurus had eaten many days worth of food to prepare for their migration.
这群肿鼻角龙拼命吃了好多天的食物，为它们的迁徙做准备。
This would have slowed them down and made them sluggish.
这会减慢它们的速度并且让它们变得笨拙。

Although Pachyrhinosaurus doesn't have the same massive size and weaponry as the other members of the Ceratopsian family, they are still pretty powerful and dangerous dinosaurs.
尽管肿鼻角龙没有角龙家族的其它成员庞大的身躯和武器库，它们仍然是非常强大危险的恐龙。
That horn can cause some fatal wounds and the fact that they lived in herds makes them that much more dangerous.
它的角能造成致命伤害，而且它们成群生活，使它们更危险。
So these Albertosaurus have got to be very careful.
所以这些阿尔伯特龙必须非常小心。
Albertosaurus fed on horned dinosaurs, duck billed dinosaurs, and even the armored Ankylosaurus.They were fearless.
阿尔伯特龙进食带角的恐龙、鸭嘴龙甚至披盔戴甲的甲龙。它们无所畏惧。
The behavior and hunting methods of dinosaurs like Albertosaurus were no different than those of larger predators today.
像阿尔伯特龙这样的恐龙其行为和狩猎方法与如今的大型掠食者没有区别。
Lions are a perfect example of how they'll seek out members of the herd and target the weakest for attack.
狮子就是绝佳的例子，它们挑出兽群中的成员并以其中最弱的为目标发动进攻。
These Albertosaurus know that a weak member of the herd is less likely to put up a vigorous defense and so their chances of being injured are reduced.
这些阿尔伯特龙知道兽群里的弱者比较不可能会奋起反抗，所以它们自己受伤的几率就降低了。
Unlike many dinosaurs, the Albertosaurus wanted to chase its prey.
跟很多恐龙不同的是，阿尔伯特龙希望追逐它的猎物。
This tired the victim and made it easier to kill.
这会让猎物疲劳，猎杀起来更加容易。
Alerted to their presence, the Pachyrhinosaurus take up a defensive stand and begin to scan the forest for their unseen attacker.
肿鼻角龙注意到了它们，于是开始采用防御姿势并开始扫视森林试图找出尚未现身的攻击者。
Realizing that the herd is aware of them, the Albertosaurus leave their hiding positions and move in towards the awaiting Pachyrhinosaurus.
知道角龙群已经注意到了它们，阿尔伯特龙离开了隐藏位置向等待着的肿鼻角龙靠近。
Pachyrhinosaurus had eyes on the side of its head, its depth perception was poor.
肿鼻角龙的眼睛在头部两侧，视觉深度感很差。
If they can cause the herd to stampede, they know it'll expose the weakest member.
如果它们能让整个角龙群奔逃，就能够从中看出较弱的个体。
Even though these dinosaurs could stand their ground against these Albertosaurus, the Pachyrhinosaurus are hard wired to flee at the first signs of danger.
尽管这群恐龙能够守住阵地对抗阿尔伯特龙，但肿鼻角龙在遇到危险的时候本能就是落荒而逃。
By turning and running away, it exposes the weakest member, it insures the health and wellbeing of the rest of the herd.
它们转身跑开时会暴露出最弱的成员，它证明了群体其它成员的健康。
This is nature's way of weeding out the sick, old and injured.
这是自然界淘汰老弱病残的法则。