Video clip of shivering monarch.
Most people assume that monarchs leave the north to spend the winter in a place that's warm.
At 10,000 feet in elevation, the over-wintering sites are often cold indeed, especially at night. These are butterflies that have fallen from the trees, often forced down by strong wind, rain, hail or even snow. If it's below 5C, it's too cold for them to fly or even crawl. Once the temperature reaches about 5C they can begin to shiver and warm themselves enough to move. Video Clip of a Shivering Monarch Play the video clip above and see how hard the monarch is working to warm up its muscles.