Monarch Migration Mania

Click here to check out uncle Davs video on the Monarch migration!!!

When I think of migrations on a large scale I think of wildebeest, flamingos and bats. But insects? The annual migration of the Monarch butterfly, Danaus plexippus is one of the largest in the word. They begin their migration in late summer from the Great Lakes state and northern plains. It is sparked by decreasing day lengths and temperatures that would otherwise make it impossible for the monarch to survive. They head in a South-westerly direction to their over-wintering site of Mexico and southern California, where the temperatures are more suitable for hibernation, mating and feeding. As they travel towards Mexico they occasionally stop to feed and roosts, accumulating in numbers as other populations converge together. In spring survivors migrate in a north-easterly direction back to their original breeding grounds. During this spring migration the monarch butterfly rarely feed or roost. How do they re-migrate without feeding or resting often to regain energy for the flight home?

This is where the report Migration of the monarch butterfly, Danaus plexippus: energy sources by J. J. Brown and G. M. Chippendale talks about how the monarch butterfly retains lipids as an energy source and as a metabolic reserve in order to re-migrate back to their original grounds.

Brown and Chippendale found that there were six neutral lipid classes and two major phospholipids present in the monarch. Triglycerides (TGL) are one of the major groups present and comprised approximately 59% of the male body and 71% of the females. In both sexes the Monarch has a large abdomen with a nutrient reserve of 93% lipid and 7% protein, and acts as a major storage area for reserves. These reserves were carried over to the adult stage from the feeding of the larval stage. Greater than 99 % of TGL were located in the abdomen where they contained 73% of the total lipid. With this said TGL is the main fat reserve that is independent from the rest of the groups. Also as they occasionally stop on the migration to Mexico the nectar they feed on is stored as sugars by glycogens. The thoracic musculature is also rich in protein and lipids but lack glycogen which stores sugars. However the thorax only contains approximately 6 % total body lipids.

FIG. 1. Relationship between whole body weight, wing length, soluble protein, and total lipid composition of individual migrating male and female monarch butterflies collected in Boone County, Missouri. ∆, Wing length; ○, lipid content; □, soluble protein content.

 This shows that the TGL in the abdomen is the major reserve lipid class compared to the thorax which contains no substantial lipid storage. The amount of lipids present is dependent upon the larval feeding activity. The results showed monarchs that were heavier and the longer wings span contained more lipid reserves than smaller adults.  As there is a large reserve of TGL lipids and only smalls amounts of proteins and glycogens the monarch rely on the fat (lipid) reserve and the sugars produced by glycogens, collected from feeding on nectar while migrating, as a source of stored energy for flight. They also rely on these to reserves to supplement the TGL reserves carried over and used from the larval stage.

So pretty much they eat and eat and store all the lipids and sugars from their larval stage and from the travel down to Mexico in order to uses it as fuel for the flight home. Which I think is awesome, taking thinking ahead to the next level!!!

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If you want to read this articles get it at :- http://www.sciencedirect.com.ezproxy.lincoln.ac.nz/science/article/pii/0022191074902182

Another article which looks at the stop-over sites of Monarchs as they migrate to Mexico is also a interesting read. find it at :- http://www.sciencedirect.com.ezproxy.lincoln.ac.nz/science/article/pii/0169534787900553

Don't forget to watch the video at the start of the blog, its a great watch!!!