The paper points out that big cat ecology and predator prey interactions in tropical regions are typically studied in natural systems.

在自然体系中，科学家热衷于研究热带地区的大型猫科动物学和捕食者与被捕食者之间的相互作用。

The first man tapped his pen impatiently against the papers, pointing at a line at the bottom where it said " signature."

第一件白衬衫不耐烦地用钢笔敲敲文件，欧维瞪着他。白衬衫指着文件最后一行写着“签名”的地方。