I was glad to be one of the few people who was able to attend Dr. Brower’s program at UMSL this year. Below are the basics from his speech/program.
He has done sixty years of research into Monarch butterflies.
This is part of a book if he ever publishes it.
There are at least 157 species of monarch-like butterflies.
Milkweed produces latex when it is damaged and is part of the plants defense mechanism.
There are at least 108 species of milkweed in north America.
Milkweed was known as far back as 1629.
Milkweed has pharmalogical properties.
Asclepias is a North American plant,but it got to Syria over 400 years ago.
It was then found in Syria and given the name Asclepias syriaca.
Monarchs fly more than 2000 miles south, spend 5 months in Mexico and then fly another 1000 miles north.
The monarch migration evolved as the milkweed evolved in North America.
Beak marks are found on Monarchs back in the 1700’s
Viceroy is similarly marked to gain the protection of the Monarch.
In tests, birds reject the Viceroy, just as much as the Monarch.
Birds in the test never ate a Monarch, but just on the basis of taste.
Toxic compounds are also bitter.
Cardenoloids were discovered in milkweed and are similar to digitoxin.
Birds were tested with bread and digitoxin solutions and they rejected pieces with higher solutions.
Raised 3000 monarch eggs and larvae on cabbage to find one that survived through the 4th instar,then switched it to milkweed. From that one,they bred many more which solely ate cabbage.
They raised more cabbage fed monarchs and fed them to birds who would teqr off the wings abnd eat the body. They then gave them monarchs raised on milkweed.
In 5 minutes the birds looked ill and in 12 minutes they were vomiting.
That’s how he became known as Brower’s Barfing Bluejays.
A month later, if you offered the same Bluejay a Monarch, it would just look at the Monarch and wretch.
They then raised monarchs on different species of milkweed to see how toxic they were.
They dried and ground the caterpillars and put them into capsule form.
They then force-fed the Bluejays.
No bluejays were killed in this process.
Each species had a different level of poison.
In one test of fall migrant Monarchs in Mass, some Monarchs had almost no toxins, while otheer hd a lot of toxins.
So some monarchs could be eaten by birds without bad effects.
Dr. Browers testing showed that a very small number of toxic Monarchs protected the entire population.
He found that you could fingerprint a Monarch to a particular Asclepias species.
Most Monarchs in Mexico have eaten Syriaca.
1975 was when Monarch over-wintering sites were discovered in Mexico.
One site he visited in Mexico was 3 hectare and had approximately 150 million butterflies.
There are two species of birds who are eating Monarchs in Mexico.
They would eat from 3500 to 35,000 butterflies/day.
There’s a 6.8 day cycle in the predation.
It suggests that birds eat a lot, get sick and then don’t eat much at all until the toxins are flushed from their system.
How can the birds eat so many of these chemically defended butterflies?
In their testing the states, 40% of monarchs are emetic?? (toxic.
but by the time they get to Mexico, only 10% are emetic.
So as they age and fly south, they lose a lot of those toxins.
Also the Orioles were stripping the Monarch abdomens and
92% of Monarchs in Mexico had syriaca patterns.
Monarchs generally lay one or two eggs on a milkweed plant.
In about 3 days the caterpillars hatch out.
They eat down their egg shell.
then they start eating the leaf an this is a very dangerous time for the caterpillars.
They can get stuck in the latex and die.
The final instar cats will bite through the petiole and will stop the flow of latex.
Then it can go to the leaf and eat it with much less latex.
Dr Brower also did the same thing to some of his milkweed and he found that it did not reduce the water content of the leaf.
He did some experiments with Monarch eggs with leaves that had been notched to stop the latex versus unnotched leaves and he found that :
1.On the control leaves which had not been cut, there were only 28% alive.
2. On the leaves where the leaves had been cut, 56% survival.
How do Monarchs build up enough energy not only to fly to Mexico, but also survive in Mexico an fly back?
By the time they get to Mexico they have a huge lipid supply.
During the fall migration – Sept 23 to October in Mass, Kansas and Florida, the average fat content was about 25 milligrams.
But by the time they got into Texas and Mexico, their fat content had gone up by 500%.
In Oct. 2011, they had one of the driest periods in Texas. and there were almost no flowers for food.
In a migrating Monarch normally, they have 71 mgs of lipids
and when they collected Monarchs in the fall of 2011, the lipids were slightly more than half in Texas.
In Mexico the average lipid count is 128 miligrams.
In 2011, they predicted that the fat count would be below normal, but some how the average was normal.
Two possibilities are that all the Monarchs with low lipids died, or
more likely there were fields in Northern Mexico where the butterflies were able to make up that loss.
California monarchs are having a hard time also. It could have to do with the drought and loss of milkweed habitat.
Monarchs have cardenolides in their eggs and all their instars into the chrysalis.
The birds learn to avoid the caterpillars very quickly.
Viceroy are probably bitter tasting but not EMETIC (vomit causing).