Monarch butterflies cling to a branch being weighed down by the sheer weight of the thousands of small bodies hibernating in the trees. As the sun peered out behind the clouds, a lone male butterfly (identified with two small black scent glands on the wings) ventured to the top of the branch in order to warm its delicate body. This photo was shot at the El Rosario Monarch Butterfly Preserve in Michoacán, Mexico. The monarch butterflies migrate in the millions to these mountains to hibernate in the oyamel fir trees, only found at a specific altitude. These individuals have never been here before, yet find the same location year after year in an incredible journey over thousands of miles.