Unintended Consequences

This is a story about squirrels and chipmunks. When you’re dealing with rodents, there is always the possibility of things going awry. There are a number of morals possible – you can add your favorites at the end.

Part of the work here involves modifying habitat so that it is more suitable for plants and animals that are losing ground in the competition for habitat, or succumbing to encroachment from aggressive invasive species. You might think that squirrels are not one of these species, but it turns out that our own Western grey squirrel, (as opposed to the non-native, ubiquitous and annoying Eastern grey squirrels) are listed as a sensitive species in Oregon, and threatened (one step before endangered) in Washington State.

The Western greys – silver-greys in the local parlance – are larger than Eastern grey and fox squirrels and have white hairs that give their fur a silvery appearance; also very big bushy tails. Western grey squirrels are denizens of oak woodlands, and of course since this habitat is much reduced, their numbers are as well. Eastern grey squirrels out-compete them in the same habitat, and they have also been over-hunted as a game species.

Our squirrel habitat project was especially fun, because as Dean (our contact at the conservation district) was learning new things, he passed them on to me. Dean had already scoped out a new section along the savanna and woodland for native squirrel habitat. The first step was to identify the species that were present, if any, using a hair trap (see below).

The trap is a tube baited with acorns or hazelnuts and some of that heavy double-stick picture hanging tape. When the squirrels go in the tube, the tape grabs a few hairs off their back. If you happen to have access to a squirrel expert, she can tell you if it is a native or a non native squirrel by looking at the hairs microscopically. Which we did, and it was a native one. The forensics were a success.

So far so good.

Dean with his hair trap

Squirrel hair trap in place with goodies

Got the hairs!

Now that the squirrels were confirmed, habitat work began. This consisted of getting rid of firs and thinning out the oaks to allow the remaining trees room to bush out and form a continuous canopy. This makes it easy for squirrels to jump from tree to tree. Larger trees offer better nest sites too, because they have larger branches and may have holes the squirrels can use for nests. Grey squirrels also use the edge of the forest near the open savanna, and I’ve seen them near the house in the firs as well, so they seem pretty opportunistic (the irony of this statement will become clear shortly).

The Doug firs and oaks were killed by girdling – chopping through the outer living layer all the way around the tree to cut off the flow of fluids. The land was too steep for good machinery access, and this method was less expensive, quicker, and had the advantage of creating some standing dead wood as a legacy.

As fungi soften up the wood in a dead tree by digesting the carbon, many organisms will move in. Beetles and other insects can be in living or dead wood; woodpeckers come looking for insects to eat and make holes which can offer nesting cavities for squirrels and other animals. A dead tree on the ground or standing will end up have more biological action going on than it did when it was alive.

Cavities in living or dead trees are part of a diverse structure in either oak or fir woods and are normally present in older stands, but not usually tree farms. Processes that create structure for habitat naturally (broken branches, fungus, insects) will produce a “messier” look, which is normal. In the absence of a lightning strike or whole tree death, mechanically limbing and topping will create an ‘artificial’ snag.

Girdling a tree makes it eventually fall over, breaking at the bottom where the cuts were made. Not so safe if you’re walking around, plus it doesn’t last as long as one that is top-killed. Topped trees tend to “melt” according to the cutter who made our snags. Altogether a longer-lasting and safer option. Since topping is a fairly expensive operation, we chose just three of the largest firs for this treatment. Some limbs are left on to prolong the life of what tree is left after the gory operation:

Tree before topping begins

Most of limbing complete. Climber checking the wind before the final cut on tree #1

Tree climber cutting the top off the third tree

The topping was pretty dramatic. It is exciting to see a fast tree climber work on these snags. See it in action:

Here is the view a few months later. It looks devastated, but the oaks will fill in over time and there will be lots of value in even the smaller dead trees as they decompose and offer perching spots as well as a carbon supply to the decomposition process.

dead trees and a snag a few months after girdling to open up oak stand

Two of the tall snags on right and left background of photo

southern edge of the Land of Moose & Squirrel w/ snag and oaks

So, after all this prep, are the squirrels just moving in, trying to decide WHICH trees to live in?


In fact, this spring and summer, I often caught site of what looked like a Grey squirrel on the ground near some of our outbuildings. It seemed quite at home on the ground. Hmmm … eventually some little squirrels materialized, and our dog seemed very excited to go out to the brush and wood piles in the yard. Could it be that a female decided she preferred the brush piles to the trees? I had never seen any reference to nests anywhere but trees, but we kept seeing these critters on the ground, running towards a hole in the ground or one of the wood piles.

Here’s where the moral begins to build: currently, there seems to be a family of two kids and a mom. They forage quite busily every morning on green apples and seeds from various trees in the yard. Ominously, they have now intersected with a bunch of chipmunks tunneling under the house and possibly living in the crawl space.

I had already tried to evict chipmunks from underneath the house. As I was contemplating my next move, I noticed the adult Grey squirrel near the chipmunk’s entrance hole – NO, not the squirrels too!

After consulting my Living With Wildlife book (chipmunks: small golf-ball sized holes; squirrels: baseball-sized holes) I realized the squirrel had taken over the chipmunk entrance.

So, we wanted squirrels? Well, now we have them – under our house. That’s what happens when you live in the woods – everyone picks their favorite spot, heedless of the wonderful natural habitat that might be just a little less comfy than your human one.

The next strategy was to see if we could get the squirrel and/or chipmunk in a live trap to make sure they were not under the house, then build some barricades. I had originally gotten a chipmunk-sized live trap, but I thought I’d see if the squirrel would fit. Sure enough – the trap was just big enough to accommodate a (smallish) agitated Grey squirrel.

Squirrel and trap next to entrance hole

We covered the trap with a towel and walked her up the hill to the official “habitat” which Tom had christened the Land of Moose and Squirrel. As she burst out of the cage, I remarked that she would probably be waiting for us when we got back to the house.

Step two of this process, as advised by the trusty “Living With Wildlife” was to dig a trench along the house, line it with hardware cloth, and hope for the best (that last is my own feeling).

the strategy – dig an even bigger hole and barricade with wire

This was beginning to feel like an arms race – small hole, large trench, what next? Was all this elaborate habitat creation up the hill really necessary if they were going to live in the ground (or with us)? I remember the excitement of seeing a family of Grey squirrels in the tree tops for the first time, now their appearance seems a bit ominous.

I finished filling in my trench, hoping it would be sufficient to foil the rodent that, after all only has its claws as tools, but can be so very pesky! There have been some exploratory holes in the old spot, but so far I’m ahead. The chipmunks are determinedly working on getting back in, though; they are even peskier and full of themselves, so I will need to extend the armoring.

A day or two later,  the alarmed-squirrel sound outside inspired me to try to get close enough to take a couple of photos. She was barking at the cat, which probably does not outweigh her, and for once did not mind me getting within range. Grey squirrels have an interesting chuckling sound as well as higher-pitched calls when they really want to get attention. At the same time she was drumming on the tree branch with her claws, sending a complicated message to whatever other creatures could speak squirrel. Squirrels are definitely more at home in the trees, where they are in command.

Western grey squirrel up a tree – where it belongs

Squirrel in scolding mode

So, do we feel like Natasha and Boris Badinov, forever plotting against Rocky the squirrel, but always losing? Well, yeah…a little.

No matter how you look at it, an endangered rodent is still a rodent – pesky and opportunistic. But it’s hard to be offended that they haven’t stayed in the woods – at least they’re here, which was the point anyway. It’s our challenge to master the art of sharing the habitat successfully.

3 thoughts on “Unintended Consequences

  1. Pingback: Time. Maps. Closeup views | GOPHER VALLEY JOURNAL

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