Close Quarters: 15,000 Butterflies on a Branch

Monarchs are famous for the spectacular colonies that they form. These photos were taken in December and January, the coldest months in the sanctuaries. The butterflies cluster the most closely when the temperatures are the coldest. They certainly are not using much space in these pictures!




Journaling Question
Some 15,000 butterflies can share a single branch--so many that the branch actually bends under their weight.

If the typical monarch weighs 500 mg, how much would a branch loaded with 15,000 butterflies weigh? (Give your answer in kilograms and in pounds. Also name another object that weighs the same amount, for comparison.)