Table of Contents
A It’s fall in North America, and millions of Monarch butterflies are migrating to warmer climates for the winter, heading either to the Californian coast or to certain mountains in Mexico. These butterflies recognise the arrival of fall in the same way that we do: they feel the chill in the air. While we adapt by putting on a sweater, the situation is much more serious for the Monarchs. Temperatures below 55 ℉ make it impossible for them to take to the air; temperatures below 40 ℉ paralyse them.
The Monarchs originated in the tropics and can’t live for long at temperatures below freezing. At the same time that the air is cooling, the nectar supply in flowers that feeds the butterflies is dwindling. To survive, they begin migrating in late summer, flying with the wind to reach their winter homes.
B Up to 100 million Monarch butterflies migrate either to California or to Mexico each year. This isn’t the entire population because some never make the migration. There are more than 25 winter roosting sites along the Californian coast and about a dozen known sites in the Sierra Madre Oriental mountains of Mexico. In both regions, butterflies depend upon trees for their survival. They cluster in pine and eucalyptus trees along the California coast and in ovamel trees in Mexico.
C Wintering Monarchs stay together. The end result looks like massive clumps of feathery orange-and-black grapes. Each butterfly hangs with its wings over the butterfly beneath it, creating a shingle effect that buffers them from the rain and creates warmth. The weight of the cluster also prevents the butterflies from being blown away. Butterflies stay in their winter homes until about March, when they begin the return journey to their summer homes, travelling as fast as 30mph at times.
D Monarch butterflies are in danger of losing both their summer and winter habitats. Summer habitats are being destroyed as more roads and new housing developments and business complexes encroach upon open space in North America (a phenomenon known as urban sprawl). As land is developed, the milkweed plant is killed. This is disastrous for the Monarch species, because once the butterfly larvae hatch from their eggs, they feed on this plant alone. Milkweed plants are also vulnerable to herbicides used by farmers, homeowners, landscapers, and gardeners.
The butterflies don’t have it easy in Mexico, either. The ovamel trees that they winter in also serve as a lumber source for local communities and big logging companies. Logging not only removes the trees, it opens up the forest canopy as well, and in creating these overhead holes, the butterflies are potentially exposed to the life-threatening elements. Each wintering site in Mexico contains millions of butterflies, and so damage to even one site could be a catastrophe for the Monarch butterfly population. Recent findings report that 44% of the ovamel forest has already been damaged or destroyed by logging.
Questions 9-14 Do the following statements agree with the information given in Reading Passage? In boxes 9-14 on your answer sheet, write
TRUE if the sataement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
9 The Monarch butterfly’s ability to fly is affected by cool atmospheric conditions.
10 The Monarch’s migratory track changes according to wind direction.
11 Monarchs that spend the winter in California favour one type of tree.
12 One reason why Monarchs collect in groups is to protect themselves from the wind.
13 Because of climate change, Monarch butterflies now spend less time at winter locations than they used to.
14 Man-made adjustments to the Mexican habitat have led to higher mortality rates.