Where Are The Monarchs?

Look around your gardens and you will not see many monarchs this year. Lepidopterists and butterfly counters are surprised by their scarcity. But their decline has been going on for a long time now. In the early 70's a group of Decatur elementary students proposed that the Monarch, Danaus plexippus, be named our State Insect, and in 1975 it was approved by the legislature. At that time overwintering Monarchs in the high Oyamel fir forests of Mexico were as dense as 25 million per acre--now that number has dropped precipitously.

What are the reasons for Monarch decline? Here are some:
                >Loss of milkweed plants in the Midwest due to Roundup Ready herbicide on crops. The herbicide kills all the weeds but the crops are genetically bred to be immune.
                >Very little nectar on their route in Texas and Northern Mexico. The 4th generation of Monarchs, which lives for many months, must travel from the states south to Mexico (some to Calif) for the winter. On their way they must survive by imbibing nectar from flowering plants. If these plants have been devastated by drought (as was the case last year), the traveling monarchs weaken and die.

                >Loss of habitat in Mexico. The forests where the monarchs overwinter have been heavily and illegally logged because the value of the timber has soared. Monarchs thus have been exposed to cold winds and sudden drops in temperature and in some years have had huge losses. Local people also chop the trees for firewood. Thus fewer monarchs go north in the Spring to lay eggs for generation A.

In a research article "Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population" (2012), John M. Pleasants of Iowa State and Karen S. Oberhauser of Univ. of Minnesota note the tremendous decline in common milkweed. These are their estimates of milkweed numbers from 1999 to 2010: 
                   31% decline in non-agricultural areas
                   81% decline in agricultural areas

The researchers conclude: "We estimate that between 1999 and 2010 egg production {of Monarchs} in the Midwest was reduced 81%."  And experts believe that the Midwest accounts for about half of the Monarch generation that flies to Mexico and elsewhere for the winter. Over 90% of all Monarch eggs are thought to be laid on common milkweed, which provides a substance that makes the caterpillars toxic to birds and other predators.

The Monarch life cycle is interesting:
           March-April: butterflies fly North and lay eggs on milkweed. Each egg forms a caterpillar which sheds skins and finally hangs upside down to form a chrysalis.  About 2 weeks after this a butterfly emerges.
           May-June: first generation lays eggs and dies, and 2d generation is formed.
           July-Aug: second generation lays eggs and dies, 3d generation is formed.
           Sept-Oct: 3d generation lays eggs and dies, 4th generation, the   "METHUSELAH" generation is formed which will live throughout the winter in Mexico and California and head back North in the Spring. 

What can we do to save the monarchs? Not much if the milkweed is eradicated by the agricultural people. They see it as a serious pest. And a homeowner who planted milkweed to help claimed on the Gardenweb site that "I truly understand the phrase 'noxious weed'"-- when he couldn't control the milkweed and found his visiting monarchs infested with OE, a protozoan parasite. 

A 59% drop was noted by scientists this year in overwintering Monarchs in Mexico. Many researchers feel this was an extreme case due to drought and other factors. They agree that things can improve. But most also feel that the situation is dire and the gradual decline of the Monarchs will be very difficult to halt. Our State Insect is in trouble.