Pests: We know them when we see them. The mice that lurk in our kitchens, the squirrels that steal our tomatoes, the mosquitoes that bite us in the summer, and the pigeons that flutter around busy city streets. And yet, in other places and times, a lot of these animals are anything but pests. They could be seen as beloved pets and important working animals, or even be revered.

So what is it exactly that defines a pest? On this episode, we investigate that question, looking at animals ranging from your everyday pigeons and rats — to more exotic creatures like Burmese pythons and Bobbit worms. We talk with a science writer who’s done a deep dive into the science of pests, find out why one mosquito researcher loves the world’s most hated insect, and hear the story of one man’s epic battle against the sea’s most disturbing creature.

Also heard on this week’s episode: