Monday, July 12, 2010

Monarch Butterflies & Disease

A fresh and healthy monarch is a beautiful treasure! But the life of a monarch butterfly isn't without its challenges. Predators abound as well as diseases. The most well known disease is Ophryocystis elektroscirrha, (O.e). It infects both monarch and queen butterflies.

O.e. is a protozoan parasite that must live in its host, the monarch or queen butterfly, to grow and multiply. The life cycle of O.e. mirrors that of the monarch. Spores are spread by an infected female monarch butterfly when she lays eggs and on the surrounding milkweed leaves. When the tiny caterpillar emerges it will eat its egg-sac then the nearby milkweed leaf, ingesting the spores. The dormant spores become activated in the caterpillars digestive tract. Once infected, butterflies do not recover. O.e. can cause smaller size, weak or severely deformed wing development and the inability to fully emerge from their chrysalis.

You can easily test a monarch butterfly for O.e. by swiping its abdomen with clear plastic tape, placing it on white index card, and examining it with a microscope. O.e. spores, when present, resemble small brown or black footballs. You can see photos of O.e. spores present with normal butterfly scales at this link:
What is O.e.?

How many monarch butterflies are infect with O.e.? Studies by Dr. Sonia Altizer and her staff at the University of Georgia show the disease appears to be linked to how far monarch butterflies fly during their migration. Here is the rate of heavily infected monarch butterflies by population:
  • Eastern monarchs (East of the Rocky Mountains): 8%
  • Western monarchs (West of the Rocky Mountains): 30%
  • Year round monarchs (South Florida)  70%
What about O.e. in Arizona? We know from the Southwest Monarch Study that monarch butterflies here migrate to both Mexico and California. A few even spend the winter in the Phoenix area. Last January Bob and I tested two monarch butterflies nectaring near the Salt River by the small overwintering site at Rio Salado and they were both negative. In February I tested three monarchs at Desert Botanical Garden that also overwintered in the area and they also were negative. The numbers are too small to be significant, but they are hopeful. The test was confirmed by David Marriott of the Monarch Program in California.

Recently we tested the frail, weathered female monarch we spotted and tagged (325U) at Wenima Wildlife Area in Springerville, AZ on June 20. She also was negative for O.e. This is especially interesting since we don't know how she entered the state - was she flying north through Arizona, or did she come in from New Mexico? In the microphotograph on the right you can see normal butterfly scales only. Again, these numbers are too small to give a full picture, but they are a beginning piece of the puzzle to better understand monarch butterflies in Arizona.

MonarchHealth is looking for more citizen-scientists to test monarch butterflies for O.e. in Arizona and report their findings for further analysis. MonarchHealth provides a kit with detailed directions to sample 30 monarchs this season. To participate or for more information contact: monarch@uga.edu.

You can watch this video link to see how you can test monarch butterflies for O.e.:
Live Monarch O.e. testing

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