And build up like that is why you should limit artificial insecticides like that around your house as well. That build up happens to each animal up the food chain. Bug gets 1 insecticide, but the lizard eats a bunch of bugs. Lizard now has 100 insecticides, and gets eaten by a snake. Snake eats a dozen lizards, now we’re at 1200 insecticide. Owl eats a dozen snakes, 24000 insecticide in the owl.

Obviously this is simplified, but it gets the point across.