Meet Monarch Butterfly Biologist
Dr. Bill Calvert


Dr. Bill Calvert was one of the first biologists to study the monarchs at their over-wintering sites in Mexico, and was certainly the one who spent the most time with the butterflies.

From 1976-1982, he and his coworkers traveled to Mexico several times each season, averaging nearly two months each year in the sanctuaries. The time in residence with the monarchs varied, but he was most often there for several weeks at the beginning of the season (November or early December) and there for longer periods at the end (February and March).

Dr. Calvert camped in the mountains, often within a few hundred meters from the colonies, and experienced the same cold, wet conditions that the monarchs endure. Here's a story:

"The worse time I ever experienced was in January of 1981 when, in spite of being deep in the tropics, a major snow storm hit our mountain camp in the Sierra Chincua," he remembers. "The storm which lasted for 10 days began with high winds, rain and some hail. About the end of the fourth day it began to snow. It rained, snowed, sleeted and blew for the next six days. Snow accumulated up to 13 inches in the clearings. We couldn't believe it. We were at latitude 19 degrees N, well within the tropics. This wasn't supposed to happen!

"Normally a local campesino friend came to the camp each day with his burro (donkey) to help gather fire wood and water. (We had an elaborate procedure to purify water set up by Richard Bartholeme who used to work for the Bell Museum of Natural History in Minneapolis. Water was boiled in earthenware crocks for at least an hour each day to keep us from getting sick. Can anybody guess why we boiled it so long when 20 minutes is supposed to do?) Everything shut down. Neither the campesino, whose name was Evodio, nor his burro, whose name was Burro Nada Mas, could get to us from his home because of the deep snow. We quickly ran out of firewood and, most important, out of heat.

"We could always melt snow for water, but we discovered that it takes an enormous amount of snow to yield much water. That turned out to be awfully difficult. Our laundry froze solid on the clothes lines.Temperatures plunged to minus 5 deg C within the colonies. In clearings where our camp was located it was much colder. Toward the end of the ten-day period when it had turned bitter cold, butterflies were falling stone dead out of their clusters.

"It was so cold in the colony that January that nearly half of the butterflies froze to death. I saw the incredible importance of the forest as a protective blanket protecting the surviving butterflies against the cold. The ones that survived were lucky in being in relatively warm pockets within the forest (we are talking minus 3 instead of minus 5) or they were the ones buried in the snow thereby insulated from the extreme cold. The forest was a mess. Many branches laden with butterflies and snow came crashing down. In several instances whole trees were uprooted. The weight of butterflies alone has never been observed to break off more than the smallest twigs. But the added weight of snow and perhaps rain frozen to the surface was enough to break branches and in a few cases uproot trees up to 6 inches in diameter."

National Science Education Standards

Life Science
An organism's behavior patterns are related to the nature of that organism's environment, including the kinds and number of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When environment changes, some plants and animals survive and reproduce, and others die or move to new locations. (K-4)

Earth Science
Weather changes from day to day and over the seasons. Weather can be described by measurable quantities, such as temperature, wind direction and speed, and precipitation. (K-4)

Science and Technology
Women and men of all ages, backgrounds, and groups engage in a variety of scientific and technological work. (K-4)

Meet Dr. Bill Calvert

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