Last week, we started looking at reptiles, including crocodiles and snakes.
上周我们学习了爬行动物，包括鳄鱼和蛇。
Today, I'd like us to have a look at another reptile -- the lizard,
今天，让我们一起学习一下另外一种爬行动物--蜥蜴，
and in particular, at some studies that have been done on a particular type of lizard whose Latin name is tiliqua rugosa.
尤其是一种拉丁名为"松果蜥"的蜥蜴，有很多研究都研究了这种蜥蜴。
This is commonly known as the sleepy lizard.
这种蜥蜴的更为人熟知的名字就是"睡眠蜥蜴"。
Because it's quite slow in its movements and spends quite a lot of its time dozing under rocks or lying in the sun.
因为它运动非常缓慢，而且花很长时间在岩石下面打瞌睡，或者是在太阳下躺着。
I'll start with a general description.
我想从概述开始。
Sleepy lizards live in Western and South Australia, where they're quite common.
睡眠蜥蜴住在澳大利亚西南部，在那里十分普遍。
Unlike European lizards, which are mostly small, green and fast-moving, sleepy lizards are brown,
不同于大多数体型都很小、身体是绿色并且运动迅速的欧洲蜥蜴，睡眠蜥蜴是棕色的，
but what's particularly distinctive about them is the colour of their tongue,
但是它们非常特殊的一点在于他们舌头的颜色，
which is dark blue, in contrast with the lining of their mouth which is bright pink.
是暗蓝色的，和他们亮粉色的嘴边形成了鲜明对比。
And they're much bigger than most European lizards.
而且它们比欧洲蜥蜴大很多。
They have quite a varied diet, including insects and even small animals, but they mostly eat plants of varying kinds.
它们吃的东西各异，包括昆虫和一些小的动物，但是大多数都是吃不同种类的植物。
Even though they're quite large and powerful, with strong jaws that can crush beetles and snail shells,
尽管它们很大、很有力量，拥有能够咬烂甲虫和蜗牛壳的下巴，
they still have quite a few predators.
它们仍然有很多捕食者。
Large birds like cassowaries were one of the main ones in the past,
像石火鸡这种大型鸟在过去曾经是主要的捕食者之一，
but nowadays they're more likely to be caught and killed by snakes.
但是现在它们更多的是被蛇所捕杀。
Actually, another threat to their survival isn't their predator at all, but is man-made.
实际上，另一种生存威胁根本不是他们的捕食者，而是人为的。
Quite a large number of sleepy lizards are killed by cars when they're trying to cross highways.
很多睡眠蜥蜴的在过马路的时候被车压死了。
One study carried out by Michael Freake at Flinders University investigated the methods of navigation of these lizards.
Flinders大学的Michael Freake开展的一项研究调查了这些蜥蜴的导航方式。
Though they move slowly, they can travel quite long distances.
尽管它们运动的很慢，但是能走很长距离的路。
And he found that even if they were taken some distance away from their home territory,
而且他发现，即使它们离自己的地盘很远，
they could usually find their way back home as long as they could see the sky.
只要它们能够看到天空，就能找到回家的路。
They didn't need any other landmarks on the ground.
它们不需要在地上有任何的其他地标。