Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [88]
My father was a bat enthusiast (in addition to his passion for ichneumon wasps and his interest in birds not to mention his pet Bulgarian weasel), and on some evenings we went out to hunt them with his shotgun. My mother, his preparator on many expeditions, skinned and stuffed them. Each species had its own flight signature in the way it fluttered or zigzagged, and the habitat where it could be found. It was challenging to learn about bats, and exciting to see them. His collection of perhaps two dozen species, which is displayed in glass-covered cases, ended up at the Bates Museum at the Hinckley–Good Will School in Maine. When I last saw those bats there in 1999, I was saddened. Not because we had killed them—their deaths, of course, brought us awareness and possibly knowledge. Rather, I was sad for the deep ignorance of those who have never seen, handled, or learned to appreciate bats, which is in part responsible for their population crashes all over the continent. Almost nobody sets out to do deliberate harm. Most evils happen inadvertently, through not knowing and uninformed notions.
At that time I did not wonder much about how bats spent the winter, nor did I (or anyone, until twenty-three years later) have a clue or care about the winter whereabouts of the monarch butterflies (Danaus plexippus), whose familiar yellow-white-and black-striped caterpillars fed on the milkweed patch next to the barn. I picked up caterpillars, fed them milkweed and raised them to adulthood in my room. I did not suspect that butterflies and bats had anything in common, nor that the continued survival of both depends on precise temperature regimes of their winter world, at pinpoints of the globe hundreds and even thousands of miles removed from the isolated Eden of the Maine woods, where they seemed part of the landscape. The official response of “protecting” these animals by making it illegal for curious kids to handle or collect them assumes that everyone wants to do it. By that logic one could just as well make it illegal to not handle wildlife, because some get enlightened by contact with it. Personally, I think that is ultimately more useful than everyone being distanced from it. Contact should be encouraged.
The monarch butterfly summers throughout the United States and into southern Canada, which is the northern limit of its food plant, milkweed. There are two major populations of the monarch that are separated by the Rocky Mountains. Those west of the Rockies migrate to the California coast in winter. There they overwinter in about forty colonies, including well-known ones at Muir Beach, Santa Cruz, and Pacific Grove.
For a long time it was not known where the eastern population spent the winter. In 1937, zoologist Fred A. Urquhart and his wife, Norah, suspecting that the butterflies migrated, started gluing tiny tags onto the wings of thousands of monarchs at their home base in Toronto, with instructions to send recoveries to them. By mapping recapture sites over a number of years, they were able to reconstruct the butterflies’ flight lines and determine that they were migrating all the way to Mexico to overwinter.
We now know that the eastern population extends from the eastern slope of the Rockies all the way to the Atlantic seaboard. Most of this population migrates south in the fall, with individuals in it traveling up to 4, 500 kilometers to over-winter in twelve extraordinarily small patches of pines and firs in the Transvolcanic Mountains in the Mexican state of Michoacan. The butterflies overwinter in these mountains at an altitude of 2, 900 to 3, 300 meters (9, 500 to 11, 000 feet) at preferred sites that have cool yet not too cold temperatures, high relative humidity, and little wind (Brower and Malcolm 1991). At one large colony where more than 14 million monarchs congregate in about 1.5 hectares