三米長的科莫多龍是全世界最大隻的蜥蜴，一口就能將水牛和鹿咬死。不過，牠沒有調節體溫的能力，寒冷時要曬太陽取暖，炎熱時要遮蔭避免身體過熱。綠森蚺可長達六米，大部份時間浸在水中靜候比自己大隻的獵物，將牠勒死。

科莫多龍和綠森蚺的祖先都是巨型動物，分別是超過五米長的古巨蜥和可長達12米的泰坦蟒蛇。不過，古巨蜥從沒像科莫多龍和綠森蚺般攀上過食物鏈頂端；而泰坦蟒蛇則要依賴非常濕熱的氣候才能維生。今日，因為處女地相繼消失，加上原生棲息地被人類入侵的情況愈來愈多，科莫多龍和綠森蚺正面臨絕種。

Mysteries of the Giants -  Reptiles, Dependent on Climate

The 3-meter long Komodo dragon is the world’s largest lizard and can kill buffalo or deer with a single bite. However, it cannot regulate its body temperature and so needs sun to warm it up or shade to avoid overheating. 

The green anaconda can grow up to 6 meters in length. It spends most of its time in the water, looking for prey larger than itself which it crushes to death.

The Komodo dragon and anaconda had giant ancestors: the Megalania, a lizard over 5 meters long, and the Titanoboa, a constrictor snake that sometimes grew to 12 meters. However, unlike the dragon and anaconda, the Megalania never reached the top of its food chain. As for the Titanoboa, it needed a very hot, wet climate to survive. Today, the Komodo dragon and anaconda are endangered by the disappearance of their virgin territories and the growing invasion of their original habitats by human beings.