Last year was my first full year raising monarch butterflies. Since the 1970s the monarch butterfly population has been declining. As the only butterfly to make a 2 way migration, the monarch butterfly can live long and go through quite a lot. Or it can have a very short uneventful life. It all depends what time during the year they come about.
Let's start with the sad facts. A monarch butterfly egg only has about a 10% chance of becoming a butterfly when left in the wild. However if those eggs are brought into a controlled environment, hatched and the caterpillars raised to a chrysalis, that changes to a 90% chance that each egg will make it to a butterfly.
That's an insane difference, isn't it?
If you guessed that is why I raise monarch butterflies, you're correct! There are lots of disease and predatory insects that affect the monarch caterpillar. Last year I lost less than 10% of my monarchs, almost all of them in the caterpillar stage. I released almost 40 healthy butterflies!
One of the other problems monarchs face is that the caterpillars only eat milkweed. It grows wild pretty much everywhere but is often perceived as a weed and most people don't want weeds growing in their yards.
Milkweed grows wild on the side of the roads which would be a good thing but many states have a mowing program and will mow it right down with no concern for the monarch caterpillars that are living on it!