Scrolling through my Facebook feed last week, I came across a stunning photo of yellow butterflies, dozens of them, in a cluster on the ground. The photographer was Sandy Holt Snide of Parkman, someone who spends a great deal of time photographing a wide variety of Maine wildlife.

Courtesy of Sandy Holt Snide

So what were the butterflies doing? I had no idea. So I messaged Sandy, hoping she’d know.

The butterflies, she said, were gathering near Harlow Pond in Parkman when she took the photo on May 9. At the time, she didn’t know what they were doing. But since then, she had done a bit of research.

The butterflies were “puddling,” she said, which means they were gathering in the puddle to consume liquid and nutrients.

She agreed to let me share the photo on my blog, and I told her I’d get some more information about “puddling” from a local butterfly expert — Phillip deMaynadier, a biologist of the Maine Department of Wildlife and Inland Fisheries who specializes in invertebrates and is a coordinator of the Maine Butterfly Survey.

The butterflies in the photo are Canadian tiger swallowtails, deMaynadier said, and they are, in fact, “puddling.”

“Other butterflies will do it too,” he said. “But the most common mud puddling butterfly people will see is the Canadian tiger swallowtail. They’re yellow and black striped, and are now on the wing, nectaring on lilacs and honeysuckle.”

Courtesy of Phillip deMaynadier
Courtesy of Phillip deMaynadier

“It’s a behavioral phenomenon,” he said. “Sometimes they’re just getting moisture, especially if it’s been a really dry, hot period. But more often, what they’re getting is trace nutrients like sodium.”

Usually when you see a large group of butterflies puddling, there’s something in the water that’s making it rich in nutrients, such as excrement, carrion (a dead animal) or urine, he said.

In fact, deMaynadier recently saw a group of puddling butterflies on a sand bar on a stream while conducting wood turtle surveys, and when he looked to see why they were concentrating in that spot …

“… it was duck poop — probably merganser poop, to be specific.”

People have known about puddling for quite a while, even if they didn’t know the exact reason for the behavior.

“It’s an old butterfly collectors trick to urinate on a dry woodsy trail, then go off and do collecting, hoping to find a mud puddling bunch of butterflies upon returning,” deMaynadier said.

Aislinn Sarnacki

Aislinn Sarnacki is a Maine outdoors writer and the author of three Maine hiking guidebooks including “Family Friendly Hikes in Maine.” Find her on Twitter and Facebook @1minhikegirl. You can also...