I have recently received several emails recently describing Gray Squirrels gathering stones. There is very little on the Internet about this behaviour, so it would be interesting to know if other people have seen it too. Below, you will also find a possible explanation for this behaviour from Don Sutherland, a zoologist at the Natural Heritage Information Centre in Peterborough. Drew Monkman
From Craig Kesselheim and Beth Dilley, Southwest Harbor, Maine, Dec. 29, 2014: We have just noticed this same behavior in our yard on the coast of Maine, and have been intrigued and mystified. It’s good to know that others have seen the same phenomenon. In our case the stones and the cache are about 20 feet apart, so we can watch the full event. The stone supply is a skirting of 1 – 3 inch stones around our garage. The cache location is among leaves under one of our ornamental shrubs.
From Ginny Clark, Peterborough, ON, Nov. 26, 2014: I finally got some pictures of the squirrel with a rock. He likes to lick it all over before he runs away along the fence to the woods behind us. I went back there, but could see no evidence of burying them, although there seem to be lots of places to hide stuff in the underbrush. It does not look like they are carrying them to their nests way up in the trees. Still a mystery!
From Carl Hymers, Peterborough, ON, Nov. 14, 2014: “Late this past summer and during the fall (September through October), we noticed that the smooth, washed, river rock stones we had used as ground cover for a garden feature were gradually disappearing. We then noticed that at least two different Gray Squirrels (black colour morph) were carefully selecting particular sized and shaped stones, placing each stone in their mouth and carrying the stones along the top rail of our fence, across two neighbour yard fence tops to disappear in the distance. Finally we decided we better remove the remaining stones, as they now had collected and removed more than a large bag and a half worth – for whatever purpose they had. It was quite intriguing to observe their behaviour, while at the same time hoping it would soon stop . This went on almost daily from September thru October and did not stop until we made the stones unavailable. The squirrels also collected the larger chunks of bark in the mulch layers on our flower beds. Who knows how the stones are being used, but maybe there are some very stable, wind proof, secure, comfortable dreys in the nearby trees with the enterprising effort of these squirrels using our stones and mulch bark as the foundation of their nest! There are at least 6 dreys visible from our surrounding trees now that the leaves are down. I will be getting larger stones for our ground cover next and the very fine chopped mulch for the flower beds next spring!”
From Ginny Clark, Oct. 15, 2014: “We have noticed a squirrel gathering small rocks (around one inch) from under our deck, then racing along to the forest area at the back of our property. It’s been happening for a few weeks now, so obviously the squirrel has not clued in that they are rocks and not nuts! This behaviour does not seem to be common. Are you aware of any reason that this would happen?”
From Don Sutherland, zoologist, Natural Heritage Information Centre, Peterborough, ON: “I’ve never seen this myself. I’ve never seen a definitive explanation for this behaviour. An alternate explanation in the literature has been that this sort of behaviour may be an attempt to disguise food caches and foil cache-pilfering by other squirrels. Gray Squirrels are scatter food-hoarders, caching food items in a wide variety of sites. When squirrel populations become dense and/or when food becomes scarce, the pilfering of caches by other squirrels becomes a problem. Caching stones, pebbles or other items may be an attempt to confuse/foil potential pilferers.”