Blue snow is similar to yellow snow

Anyone who lives "up north" understands why you don't eat yellow snow.  But I didn't realize that blue snow has a similar origin.

“Eastern cottontails... sometimes eat buckthorn branches and bark, especially toward the end of winter,” Minneapolis Parks wrote on social media. “Buckthorn contains a phytochemical that turns urine blue after being exposed to sunlight.”

Buckthorn is a non-native, invasive plant that crowds out native shrubs and small trees that provide habitat for many species of birds, according to the Department of Natural Resources. So blue rabbit urine is a sure sign there are some plants nearby that ought to be removed. (Buckthorn is such a problem in Minnesota that it is illegal to import, sell or transport it in the state.)

In case you were wondering, Iowa-based Blue Bunny ice cream got its name from a child who saw blue rabbits in a department store window, not their brightly colored excretions.

Good for them for eating the buckthorn, which I have to repeatedly grub out from the small woods behind our home.  Image cropped for size and emphasis from the original in the Minnesota Star Tribune.

A relevant article from the Mayo Clinic on the rainbow of (human) urine colors.