Monarch butterflies flutter around the globe
Photo: Mario Vazquez/AFP/Getty Images
Some researchers have seen a steady decline in the numbers of monarchs that travel to the Oyamel forests in Mexico. They think the decline might be due to the loss of forest from logging, the occurrence of droughts in the United States and the removal of milkweed, which larvae feast upon before becoming a caterpillar.
Read more: Fewer monarch butterflies are becoming 'snowbirds'