Where have all the Squirrels Gone?

An Eastern Grey Squirrel in the Author’s back yard munching on some cracked corn. Kinnelon, New Jersey, USA. Photograph by Author

While we were dealing with 2020, few of us in North Jersey noticed the nearly complete lack of acorns, but you can be sure the chipmunks and squirrels noticed it! But now this year you may be noticing something different — the lack of chipmunks and squirrels. What you’re observing is part of a natural cycle that follows an amazing event known as Oak Tree Masting.

Ecologist Dr. Dustin Partridge explains that it’s the aftermath of “Oak Tree Masting.” We both live in Kinnelon, New Jersey, USA which is located an hour’s drive from New York City, nestled in the heart of “The Highlands,” a wooded hilly region about halfway between New York City and Pennsylvania.

Ecologist Dustin Partridge, Ph.D. on Lake Kinnelon, New Jersey, USA. Photograph by Author

Oak Tree Masting

“Masting happens every few years when all the trees signal to produce extra acorns/oak nuts, as a reproductive strategy. Basically, if they produce tons of seeds they ensure that the local wildlife will be full before they’re able to eat all the seeds produced. It’s a way to make sure a few of the tree’s offspring survive,” said Dr. Partridge.

The Oak Trees Communicate with Each Other

Whoa. Time out. Oak Trees are talking to each other? The Tree of Souls is a giant willow-like tree within James Cameron’s Avatar whose roots are capable of initiating neural links with species living on the fictional planet of Pandora. That sounds crazy. But really, it’s not too far from reality!

If Oak Trees know when the next masting year is, they are not saying. It’s not on a predetermined schedule as with Periodical Cicadas and their 13 or 17 year breeding cycles (prime numbers for what it’s worth). So unlike the confidently predicted arrival of Brood X currently underway, the next Oak Tree Masting is a closely guarded secret, apparently known only to the Oaks. How they decide and how they agree on it is still largely a mystery. Their root systems might pass signals to each other with the aid of fungal structures called Mycelia. But Oak Tree populations bifurcated by large river systems still sync with each other. So weather patterns might also play a role in their collective decision on when to drop a mass quantity of acorns on my driveway. I mean the forest floor.

Regardless, the casual observer is left marveling at the interconnected nature of our natural world and how much we have yet to learn about it.

Bumper Crop of Chipmunks and Squirrels

Faced with this abundance of food, Our local Eastern Gray Squirrels and Eastern Chipmunks produce more offspring during an Oak Masting year and in the following spring. This is what we witnessed here in spring 2020 while working from home and looking out the window at our backyards. Acorns emerge in the late summer and early fall as a perfect winter food for squirrels and chipmunks to stow away just as the weather starts to turn cold and the other food sources are depleted. They are high in protein and come individually wrapped and preserved in their own recyclable single serving container. Squirrels and Chipmunks are especially fond of them.

So the spring after a mast year usually begins with an abundance of squirrels and chipmunks, but this time it began also with many of us working from home, starting our first vegetable gardens just to see them overrun by hungry furballs. Dr. Partridge himself laments that he was “left without a single tomato or peach,” in reference to the abundance of acorn eating rodents.

Rodent Population Response to Oak Nut Masting. Graphic by Dustin Patridge, Ph.D.

To make matters worse, Oak Trees produce far fewer if any acorns in the year following a Mast Year. So as other food supplies dwindle and at about the time when acorns would normally be falling and right as Squirrels and Chipmunks likely have exhausted much of the non-acorn food supply, there are almost none to be eaten or stowed.

I maintain a local Facebook Page with a decent local following of other wildlife enthusiasts who were observing squirrel roadkill in unusually high numbers last fall and one incredible report of swimming squirrels in a lake.

Dr. Partridge has witnessed the swimming squirrel behavior in his work and recalls a time years ago when one hungry, tired wet squirrel came and rested on the stern of his boat. This type of risky behavior increases for various reasons including a shortage of food and biological dispersal, and it is likely to increase in the year following an acorn masting.

People are noticing the absence of squirrels and chipmunks right now, because the 2019 Oak Masting caused an increase in the number of squirrels and chipmunks living around here in the spring and summer of 2020,” reasons Dr. Partridge. “It’s a perfectly natural cycle. However, I’m inclined to say everyone is noticing the lack of rodents this year because so many of us were home through much of 2020 gazing at the backyard and really noticing the local wildlife.

-Dustin Partridge, Ph.D. Ecologist

Eastern Chipmunk (with predator, a Red Fox). Kinnelon, New Jersey. Photograph by Author.

Most Oak Trees are Planted by Squirrels

Most Oak Trees are planted by squirrels. You heard that right. An oak sapling has almost no chance of survival if growing in the shadow of the tree it fell from. They are designed to roll and that certainly helps. But what the Oak Tree really wants is for a squirrel to take it, bury it, and either forget it or not need it.

Eastern Gray Squirrel, with acorn. Kinnelon, New Jersey. Photograph by Author

Most Oak Trees are planted by squirrels who buried an acorn and did not retrieve it. Some are just not needed and some are lost or forgotten. Squirrels are able to find and stash over 25 acorns in an hour. It’s all a numbers game. And a shell game. Most of the acorns are subsequently moved to thwart would-be cache raiders spying on the squirrels’ hard work.

Squirrels do not aim to retrieve all of their acorns by winter’s end for the same reasons we humans land our airplanes with fuel still in the tank. Just enough is not enough in practical terms. Nor are squirrels even able to retrieve all of their winter food stashes. One study found that Squirrels are able to find about 95% of their buried acorns in a controlled environment, while other studies put the acorn recovery rate at closer to 25%.

Oak Tree Masting Helps Forests Regenerate

An Oak Masting every two to five years helps this tremendously. A single Oak Tree can produce over 10,000 acorns in a mast year. This tricks the Squirrels into hoarding more than can be consumed by the squirrels or the thieves and leaving them scattered and increasing chances that the seeds will eventually germinate near a patch of sunlight.

Ready set go! A Race to the Top

When a tree falls in the woods, a huge patch of sky opens up and a race begins. Maple saplings from their helicopter wing seeds are competing with saplings coming out of the roots of Beech trees and others.Oaks want their shot. And the squirrels have given them one. The journey of a tree to the top of the forest canopy is a long and perilous competition with other saplings and flora, and all at the mercy of herbivores.

So why do oak trees do this? “To ensure their offspring survive,” explains Dr. Partridge. What’s easy to miss in a deciduous forest is the slow motion race for sunlight that begins when a patch of sky opens up, such as when a tree falls. Saplings will compete to fill that gap and oak trees want a fair shot at it.

A dead Oak Tree and a live Eastern Chipmunk. Each ring in the trunk represents a year of the Oak Tree’s life which came to an end shortly before the author discovered it lying across the road while testing the all wheel drive, breaks, independant suspension, and ice tires of his Subaru Outback one dark, snowy, windy night. Kinnelon, New Jersey, USA. Photograph by Author

It’s a cycle that’s been repeating for a very long time. Keep your eyes peeled for oak tree saplings that our Squirrels have been tricked into planting for them.

References

Columbia Journalism Review. “A ‘Mast Year’ for Acorns.” Accessed May 19, 2021. https://www.cjr.org/language_corner/mast-bumper-crop-acorn.php.

ago, Emma Bryce-Live Science Contributor over 2 years. “How Do Squirrels Remember Where They Buried Their Nuts?” livescience.com. Accessed May 19, 2021. https://www.livescience.com/64104-how-do-squirrels-find-buried-nuts.html.

The Adirondack Almanack. “Gray Squirrels, Oaks, and Acorns -,” December 18, 2019. https://www.adirondackalmanack.com/2019/12/gray-squirrels-oaks-and-acorns.html.

Hacket-Pain, Andrew J., Andrew D. Friend, Jonathan G.A. Lageard, and Peter A. Thomas. “The Influence of Masting Phenomenon on Growth–Climate Relationships in Trees: Explaining the Influence of Previous Summers’ Climate on Ring Width.” Tree Physiology 35, no. 3 (March 1, 2015): 319–30. https://doi.org/10.1093/treephys/tpv007.

Kelly, -John. “One Paw Washing the Other: Oak Trees and Squirrels Have Evolved to Help Each Other.” Washington Post, April 8, 2014, sec. KidsPost. https://www.washingtonpost.com/local/one-paw-washing-the-other-oak-trees-and-squirrels-have-evolved-to-help-each-other/2014/04/07/9b2a57fa-ba89-11e3-9a05-c739f29ccb08_story.html.

Koenig, Walter D, and Johannes M H Knops. “The Mystery of Masting in Trees,” 2005, 9.

Ned Hardy. “Millions Of Trees Are Planted Every Year By Squirrels Who Forgot Where They Buried Their Nuts,” February 10, 2020. http://nedhardy.com/2020/02/10/squirrels-plant-trees/.

The Botanical Journey. “Oaks & Acorns: The Mystery of the Mast.” Accessed May 19, 2021. https://thebotanicaljourney.com/blogs/the-botanical-journey/oaks-acorns-and-the-mystery-of-the-mast.

The Botanical Journey. “Oaks & Acorns: The Mystery of the Mast.” Accessed May 26, 2021. https://thebotanicaljourney.com/blogs/the-botanical-journey/oaks-acorns-and-the-mystery-of-the-mast.

ScienceDaily. “Researchers Tackle The Nutty Truth On Acorns And Squirrels.” Accessed May 19, 2021. https://www.sciencedaily.com/releases/1998/11/981126102802.htm.

HowStuffWorks. “Squirrels Actually Organize Their Nut Hoard — Here’s Why,” September 28, 2017. https://animals.howstuffworks.com/mammals/squirrels-really-organize-nuts.htm.

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Michael lives out in the woods with a camera and a computer.

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Michael Bateman

Michael Bateman

Michael lives out in the woods with a camera and a computer.

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