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How is a tree-trunk like a hot water bottle?

Hot water bottles are filled with hot water. People snuggle next to hot water bottles to warm their bodies. Trees are also filled with water. When butterflies nestle tightly on a tree trunk, the warmth of the tree keeps the butterflies warmer than the surrounding air.

"When the temperature drops down really low, you'll see millions of Monarchs just festooning these beautiful trunk clusters. If you think about it, the bigger the tree, the more heat it holds. So this is an argument for maintaining the forest in its native state, to let the trees get as big as they can, and the butterflies will be protected during those cold periods," Dr. Lincoln Brower told NOVA.

Photo: Dr. Lincoln Brower