A Hard Nut to Crack: The Red Squirrel’s Method

The Black Walnut is common in Eliza Howell Park and is very popular with squirrels, especially the Red Squirrel. In the fall, I love to watch these little “critters” as they energetically harvest the nuts from the trees (See “The Red Squirrel: A Different Walnut Hoarder,” September 25, 2018).

In the winter, I find clear indications that the hoarded walnuts are being consumed.

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Anyone who has attempted to crack open the hard-shelled black walnut to get the nutmeat knows how difficult it is to crack these shells open at all and how difficult it is to do so without shattering sharp pieces all over. It is impressive to see how neatly these shells have been opened and emptied.

Every nut is opened in almost exactly the same way. In this close-up, the marks left by the cutting teeth are clear.

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What might not be evident from the picture is that the squirrel opens each nut twice, once on each side. The next picture of the same nut, side 1 and side 2, is more evidence of how systematically the opening method is used.

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Not all squirrels open walnuts in the same way. A few of the open shells I have found look very different, opened by a different species. 

Here is an example.

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Though I have not had the opportunity yet to watch it in the act of cutting open a walnut, I am quite sure that it is the Red Squirrel, not a Fox Squirrel or a Gray Squirrel, that uses the method of opening the nuts from both sides.

The two-sided open shells are usually found together in a cluster and Red Squirrels hoard their nuts in a larder while Gray and Fox Squirrels scatter hoard. Further, these shells are found in the very same park locations where I often see Red Squirrels; the two locations I found clusters so far this winter are the two locations I checked because of earlier sightings of the animal.

The Red Squirrel (photo by Margaret Weber):

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The Red Squirrel is the smallest and least common of the tree squirrels in Eliza Howell Park, but, to me, its behavior is the most fascinating.

The Red Squirrel: A Different Walnut Hoarder

On my late September wanderings in Eliza Howell Park, I often check the walnut trees hoping to catch sight of a Red Squirrel harvesting walnuts. Sometimes the sound of falling walnuts tells me where to look.

Of the three species of tree squirrel in EHP (Fox Squirrel and Gray Squirrel, which is present in both gray and black variations, are the other two), the Red Squirrel is the smallest, the least common, and the most energetic walnut hoarder.

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The Red Squirrel, sometimes known as “pine squirrel” because it is so often found in conifer forests, also lives in hardwood forests. They are not as comfortable in cities as Fox Squirrels and Gray Squirrels and I do not see them in the yards of our Detroit neighborhood, despite the large trees. Eliza Howell Park is a natural enough setting for a few of them to make a home.

Those not familiar with the Red Squirrel may find it helpful to note the differences from the Fox Squirrel, which is also reddish.

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All three species of EHP tree squirrels store and eat walnuts, but the Red Squirrel takes a different approach. “Hoarding,” in animal behavior, simply means storing for later use. There are two general types of hoarding by animals that collect nuts – scatter-hoarding and larder-hoarding.

Gray and Fox Squirrels are scatter-hoarders, hiding the nuts separately in different locations. (Blue Jays are also scatter-hoarders of acorns; see my “Blue Jays Harvesting Acorns,” August 27, 2018.) Larder-hoarders cache their food together in a central hidden location. Red Squirrels are larder-hoarders.

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There are a large number of Black Walnut trees, of all sizes, in Eliza Howell. By late September the leaves are starting to turn yellow. The large nuts, which have been noticeable for a couple months already, are also now changing from green toward yellow.

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If I am in the right place at the right time, I watch the Red Squirrel in its walnut harvesting. It runs from one nut to another very quickly, pauses a second to decide whether the nut meets its quality standards, then (if it does) clips it off and lets it fall while it rushes off to another. I have watched as one squirrel dropped about 10 nuts from a large tree in less than a minute, then descended the trunk with another in its teeth.

As I watched, I wondered how many it would be able to find in the thick shrubs and brambles all around the tree. And I wondered where its larder was.

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I have not yet found a Red Squirrel walnut larder. I have several times found concentrations of walnut shells on the ground in the winter, suggesting a squirrel’s favorite eating spot, but it is something else to find the larder. Maybe this winter?