Through the theories of Darwinism, they certainly wouldn't have survived through the ages because they were the strongest or the fittest, but they have survived because of their poison and their inclination to live in large groups. Within only 150 years, North American industry has boomed and with this change, monarchs have been put in a perilous position. There is a huge demand for land and timber. Oyamel trees, where the monarchs roost during the winter, are being logged. Huge forests are being destroyed.
Few people care about the conservation of monarchs.
In Canada, the only plant that monarch caterpillars can feed on, milkweed, is destroyed because it is considered a noxious weed. Pollution from cars and cities poison the monarchs. Their habitats are being destroyed, and thousands of their lives are being destroyed with it. It's hard to make that choice, so hard that few people have decided upon this question and taken action. For Mexican timber workers, Canadian poison control personnel, and commuters, the solution is simple, humans are much more important than butterflies.