Relict Behavior

In general, animals act in ways that help them to survive within their specific habitats. However, sometimes an animal species may display a behavior that no longer serves a clear purpose. The original purpose for the behavior may have disappeared long ago, even thousands of years before. These behaviors, known as relict behaviors, were useful to the animal when the species’ habitat was different; but now, because of changed conditions, the behavior no longer serves its original purpose. Left over from an earlier time, the behavior remains as a relict, or remnant, long after the environmental circumstance that influenced its evolution has vanished.

OK, ah..so a good example of this, found right here in North America, is something an animal called the American pronghorn does. Pronghorns, as you may know, are a kind of deer-like animal. They live out on the open grassy plains, somewhat in the middle of North America. And they are super-fast.

Pronghorns are in fact noted for being the fastest animal in the western hemisphere. Once a pronghorn starts running, zoom, none of its present-day predators, like the bobcat or coyote, can even hope to catch up with it. It’s off in a flash OK, so why then do pronghorns run so fast? That’s the question. Well, it turns out that quite a long time ago - I’m talking tens of thousands of years - things on the grassy plains used to be very different for the pronghorns, because back then, lions used to live on the plains, chasing and preying upon the pronghorns And lions, of course, are a very swift-moving mammal, much faster than the bobcat or coyote or other predators that you find on the plains today.

But now, however, lions are all extinct in North America There is no longer a predator of the pronghorn Tens of thousands of years ago, though, the lions were there, chasing the pronghorns, so back then, the pronghorn’s speed was critical to its survival.

遗留行为 

一般来说，动物的行为方式有助于它们在特定的栖息地中生存。然而，有时一种动物可能会表现出一种目的或功用不明确的行为。这种行为的最初目的可能在很久以前就消失了，甚至在几千年前。 这些行为被称为遗留行为，当物种的栖息地不同时，这些行为对动物是有用的;但现在，由于条件的改变，这种行为不再满足其最初存在的目的了。在影响其进化的环境消失很久之后，这种从早期遗留下来的行为作为一种残留的行为而遗留下来。 

好的，这有一个很好的例子，在北美有一种叫做美洲叉角羚的动物。你可能知道，叉角羚是一种类似鹿的动物。 它们生活在开阔的草原上，差不多在北美的中部。 而且它们非常快。  

事实上，叉角羚是西半球跑得最快的动物。一旦叉角羚开始奔跑，嗖，现在的捕食者，如山猫或土狼，甚至都没有希望追上它。那叉角羚为什么跑得这么快呢?这是个问题。 嗯,事实证明很长时间以前,我是说成千上万年前，草原环境对叉角羚是非常不同的,因为在当时,狮子住在平原,追逐和掠夺叉角羚。狮子,当然,是一个行动非常迅速的哺乳动物,比山猫、土狼或其他你今天在平原上发现的食肉动物快得多。  

但是现在，北美的狮子都灭绝了。现在已经没有叉角羚的捕食者了。然而，数万年前，狮子还在那里，追逐着叉角羚，所以在那个时候，叉角羚的速度对它的生存至关重要。