Monarch Butterfly Decline and Tropical Milkweed

Monarch butterfly numbers that overwinter in Mexico have seriously declined. Have they ever been this low before? Truthfully, scientists do not know when and what their lowest numbers were in history. Their numbers have been recorded from 1994 until now. Numbers were not recorded before 1994. In fact, the overwintering grounds were not discovered until the 1970′s. Local Mexican people knew about the sites but no one else knew about them.

No one knows the numbers from back during the dust bowl days and other times in history when there were severe droughts for years on end. PROBABLY the winter of 2013/2014 is the lowest it has been in history. It may have been higher than some years in history. We do not know. It is the lowest in KNOWN history.

1. Monarch butterflies are NOT going extinct. The MIGRATION is considered by some scientists to be in danger. Other scientists say no.
~ There are populations all over the world.
~ There are year-round populations of Monarch butterflies in southern Florida and southern California that never migrate.
~ We should plant milkweed and nectar plants whether the migration is going extinct or not. Milkweed has been removed from many millions of acres of farmland. The more we plant, the better for Monarch butterflies.

2. The only reason tropical milkweed (Asclepias curassavica) is not a US native is simply because line that divides the US and Mexico was drawn on maps a few hundred miles north of tropical milkweed’s native range. If the US/Mexico borders had been further south, tropical milkweed would be a US native.
~ In this case, ‘native’ is simply the matter of a line on a map.
~ Tropical milkweed is native in the area through which Monarch butterflies migrate.

3. Some people claim that tropical milkweed causes more OE infections in Monarch butterflies.
~ OE spores are on any milkweed that a contaminated adult butterfly touches.
~ Tropical milkweed doesn’t become infected with OE. OE can only infect butterflies and then only those in the Danaus family. Milkweed can never HAVE OE. Many people are so confused by this that they won’t keep seed from one season to the next.
~ Milkweed (every species, not just tropical milkweed) becomes CONTAMINATED with OE spores.

4. There are often more spores on tropical milkweed simply because Monarch butterflies like tropical milkweed better than some other species of milkweed.
~ Think about a full candy jar and an empty cookie jar in a room full of sick children. The candy jar lid will be covered with germs (from sick children’s hands) and the cookie jar lid would be clean. If the candy jar is empty and the cookie jar is full, the candy jar lid won’t have germs from sick children. Instead, the cookie jar will have germs.
~ If tropical milkweed was eliminated, the spores would be on other milkweed plants. They wouldn’t disappear.

5. Some people want tropical milkweed eliminated from the US.
~ If tropical milkweed was eliminated from nature, even for the winter, year-round populations of Monarch butterflies and Queen butterflies would dramatically decrease and possibly disappear. Although there are other species of milkweed that stay green all winter, they won’t support a huge population such as south Florida enjoys.
~ Some people believe that tropical milkweed is dangerous because it stays green all winter where temperatures do not drop to freezing or below. Some other native milkweeds stay green in south Florida. Tropical milkweed isn’t the only species that stays green.

6. OE is deadly but only in extreme cases.
~ If OE was as deadly as people often think, south Florida wouldn’t have a year-round population of Monarch butterflies. The south Florida population in the Miami/Dade area is considered to be 100% contaminated with OE. Yet there is a non-migrating year-round population of Monarch and Queen butterflies in south Florida, many of them with OE.
~ Most heavily infected adult butterflies fly, mate, and lay eggs. If OE was as deadly as we are led to believe, OE would kill itself. OE must keep the adult healthy enough to fly, mate, and lay eggs to spread itself to infect other Monarch and Queen butterflies.

7. Some people claim that tropical milkweed stops migration.
~ The highest recorded migration number overwintering in Mexico was in the winter of 96-97. In 1996, tropical milkweed was growing in the US, planted in gardens all over the country as well as some grown in Canada. Tropical milkweed, according to plant experts, had been growing in the US for decades, possibly centuries.
~ Tropical milkweed is native to and grows in Mexico. Even if it were totally eliminated from the US, they continue to fly over it and drink nectar from it once they reach Mexico. If it were to stop migration, it would have stopped migration long ago.

8. Monarch numbers can rebound.
~ In the summer of 2014, numbers almost doubled.
~ In the summer of 2015, numbers increased three and a half times over the previous year.
~ In the summers of 2016 and 2017, numbers dropped again, but not as low as they were in either 04-05, 12-13, 13-14, or 14-15.
~ If numbers double in the summer of 18 and again in 19, numbers will be the fourth highest number since we started monitoring the overwintering sites in Mexico. If the numbers doubled again in the summer of 20, the numbers would be higher than has been ever recorded. That being said, numbers usually don’t double two years in a row, but the numbers clearly show that it is possible for Monarchs to totally pull out of the current slump.