Woodchucks are called groundhogs and whistle pigs for a good reason: they spend six months gorging themselves before going into hibernation. If they don’t double their weight, they might not survive the winter. (Thanks to Chris Mayer for sharing her expertise and Ariana van den Akker for her photography.)

If you want to make your own natural history observations, The Naturalist’s Notebook by Nathaniel T. Wheelwright and Bernd Heinrich (Storey Publishing, 2017) provides guidance and a systematic format, with 100 percent of royalties going to conservation and environmental education.

Check out more Nature Moments—and the series’ new website, which lets you search by topic or season.