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