Thank you for your question. For general information about monarch butterfly studies, you can contact the following web site:

http://www.MonarchWatch.org/

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Now let me address your question, "Why are monarch butterflies endangered of dying?"

Actually, some disagreement exists on this point. First of all, you must remember that monarch butterflies are insects. That means that they can reproduce very fast when they have adequate food plants for the caterpillars. Personally, I cannot believe that the species will perish, although we might see reduced numbers of those butterflies if we are not careful about conservation.

Monarchs face three major problems, as follows:

1) Monarch caterpillars feed only on milkweed plants. However, those plants usually do best on farmland and along roadsides. Farmers and highway caretakers regularly mow or spray those plants with herbicides. Those actions result in fewer monarchs raised.

2) A microscopic parasite exists on these butterflies and apparently causes deaths in caterpillars. The adult butterflies unwittingly transmit this parasite as they fly from plant to plant while laying eggs. We have a problem here. If we have a great many monarchs, the disease can spread faster.

3) Monarchs cannot survive really cold weather in any stage of their life cycle. Thus, we consider them a tropical or sub-tropical butterfly. During the winter a great many of them overwinter in particular aggregation sites in southern Mexico and California. Some butterfly experts believe that severe alteration of those overwintering sites will destroy their migratory behavior. I take a less extreme view. I don't believe we know
enough about Nature to know whether that is the case.

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Again, thank you for your interest in monarch butterflies. We need more people like you.

Monarch Butterflies require milkweed plants when they are in their caterpillar stage of life.With the development of California, much of these areas were cut down and made into homes, shopping centers and parking lots. You see, with the reduction of this one plant, you basically lower the potential for reproduction of the butterfly.

Your question is not really a question about biology--it's a question about people and economics. Why do we, as people, feel the need to have big yards for our houses, with
big malls to shop in and big roads to drive our big cars on--I think if you look more at the sociological aspect of how people want a certain standard of living and couple that with why some people feel it is ok to develop land to the point that half the business and half the homes are unoccupied, then you might see that your question was more about people and economics and not really about a very pretty butterfly.

If you want to help the butterfly--plant milkweed--it's not a pretty plant, but it is necessary for the butterfly.

In a way, you have just answered your own question. People aren't sure of why the butterflies are dying so they do studies to find out. There are maybe three general theories though that apply to many endangered species. First, their habitat is being destroyed so that there isn't enough food, places to breed, or just live. Habitat destruction can be many things; people cutting down trees, cows eating vegetation or trampling the habitat. Second, people or their pets or animals are causing more of the butterflies to die. This could be many things also like a nearby road where butterflies get hit by cars as they fly across. Third is that invasive species are coming into the butterflies habitat and taking over. This could be other butterflies or predators like lizards that may be especially good at catching the butterflies. The cause could also be any combination of these. Can you think of any other reasons?