Strange Stains in the Snow

About a month ago, I started noticing spots like the one in the photo above around my yard. The color isn't exaggerated - it's really that blue. Like mouthwash. Or antifreeze. But I don't imagine that something worrying about fresh breath is rinsing and spitting in the back yard or that some nut is pouring antifreeze around on the snow. The patches reminded me of something I saw at the nature center about ten years ago.

I was hiking with a group of students when we spotted a patch of blue snow. It was near juniper bushes. After the class was over, I did some research and learned that if rabbits eat juniper berries it can turn their urine blue.

Looking at the stains in my backyard, I was pretty sure rabbits were responsible. As I explained in earlier posts, my yard has been overrun with rabbits this winter. Any time it snows overnight, the yard is trampled with rabbit tracks by morning. So, the source of the blue patches seemed most likely to be rabbits. But not because they were eating juniper berries - there aren't any junipers in the area. Time to do some research again.

Since the last time I looked up information on-line (early in the 2000s), some new ideas have been found. According to an article published by the Ontario Woodlot Association, when rabbits are desperate for food, they'll eat bark from things they would avoid otherwise - stuff like buckthorn. (Ah, yes - wonderful buckthorn.) The author of the paper did an experiment - he feed pet rabbits buckthorn. Once they peed in the snow, the color went from yellow-brown to bright blue within about ten minutes on sunny days. (www.ont-woodlot-assoc.org/sw_nonfibre_redskies.html) I know there's buckthorn around and the amount of snow could make it challenging for the rabbits. So, I think the mystery is solved. Now if only the nibbling would kill off the buckthorn...