Our habitats, their habitats

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Types of Habitats for Squirrels on WashU Danforth Campus 

For Squirrels, there are basically two types of habitat. One is for food resource, and the other is for building nests or caves. Of course, the trees where they usually build nest also can provide food, but only the ones that are tall and strong enough with many natural caves can be the preferred options for squirrels to live in and have litters.

On WashU Danforth campus, there are around 4,000 trees in 160 species, where many of them can be our Eastern Gray Squirrels’ habitats.

For food resources, they can eat seeds or berries from walnut, pine, oak, cedar, hemlock, spruce, hawthorn, mulberry, hackberry, locust, locust, tulip, hickory, crabapple, pear, or even persimmon, paw paw or dogwood trees.

Impressively, according to No Nuts, No Problem: Squirrels Harvest Maple Syrup  by John Roach at National Geographic, squirrels even can also survive on maple sap.

For their ‘residential’ spaces, they prefer oak, walnut, hickory, beech, elm, tulip poplar or sometimes cottonwood.

You may notice some of the food resources for squirrels are also edible for us, such as crabapple (for jam), pear, persimmon, pawpaw, and mulberry, although we do not tend to eat them as there are way better options for us.

When we do not need these available food resources, we would like to see animals playing around on the trees which bring us joy. However, if they accidentally invade our habitats, such as starting to live on our attics, or disturb our construction activities, this mutually beneficial relationship will be one-sided broken by us, and leave other species very little options.

Definition of Habitat

In Oxford and Meriam-Webster dictionary, the word “habitat” basically has two common definitions – the place where animal or plants grow or live, or residential dwelling places for the human.

Is there a chance that these two concepts can positively intertwine? How do we share our common resources wisely enough to create a healthy urban environment, not only ecologically, but also respectfully? How do we “communicate” with squirrels despite they can not really talk in order to know their feelings about our disturbance? The Squirrel Relocation Service team will keep digging into this question.

How do we act in the ‘network mutualism’ between squirrels and human?


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Through tracking the scent, this squirrel in the alley successfully found the acorn he/she hid under the ground. But will all squirrels be smart enough to find food in disturbed habitats?



The alley is under construction for the upcoming carnival



‘Network mutualism’, a concept mentioned in Rod Barnett’s book “Emergence in Landscape Architecture”, where he describes the relationship between coyotes and human in Auburn as such.

“While coyotes do not prey on humans, the reverse is often true, so the human- coyote relationship, could be said to be that of a predator species to its prey. Even though humans do kill coyotes, they are not dependent on them for food.

Ecologically, therefore, their relationship might be seen as commensal, where one species, the coyote, benefits from the habitat created by urbanization, while the other, the human, is not affected in any significant way. Or it is more accurate to say that the two species are equally involved what is sometimes called a network mutualism.

The coyote population distributes itself throughout a space without borders or enclosure.

Organized by the rule of law, human Auburn is a static space defined by walls, enclosures and paths between enclosures, a division that nonhuman Auburn is continually redefining as a smooth continuum of “habitats”, “ecotones”, and “biotic communities”.

Just like these coyotes, we and squirrels also have this network mutualism, despite occasionally they go to people’s attics to live, and we human disturb their habitats by constructions, such as the one for the coming carnival.

When the land is stripped, some squirrels are still smart enough to find where they hid their food by smell, but it is doubtful that if all the squirrels are as smart as the one we filmed.

We all know animals’ habitats not only benefit themselves but bring us ecological diversity. However, the value of their habitats is beyond that. Their old habitats equal to “historic sites” in human societies, although may going through a faster pace of reconstruction. It is one part of the public history that documents the evolution of the human and non-human relationship.

As Rod Barnett says in his book: “Public space, may well, in fact, be the primary site of this encounter, if we extend the notion of the public to include nonhumans.”

So here is the question, how do we not disturb squirrels’ habitats while doing our necessary construction?

The first step might be, recognizing the public space is “public” for everyone, even beyond human.



Symbiosis of Squirrels and Pin Oaks


Check out the full image here

Timeline-02A deep relationship between squirrels and pin oaks are shown in our research as above. Even though pin oak is a fast growing tree, compared to squirrels, it has such a long life cycle. However, they work and live intimately together year after year, generation after generation and witnessing each other’s growth or even evolution in the long history of ecology.

On-site Squirrel Cavity Studies

Cavity on Site

Cavity Activity Map

According to “What’s That Clump of Leaves?” by Art Shomo, there are two types of nests: tree cavity dens and leaf nests. The nest is at least 20 feet up to the tree,  and during winter, the squirrels move the nests from the outer branch to the main trunk to get more stable structures, by weaving twigs and compacted leaves together. Dens are good for keep squirrels’ body temperature and protect them better from extreme weather conditions, which are usually with 6 to 8 inches diameter. Oaks, beeches, elms and red maples are ideal trees for squirrels to build dens or nests. In the author’s study area West Virginia, gray squirrels prefer dens more than leaf nests.

On our site, there are many trees with possible cavities, especially the area where the red circle is at on the “Squirrels’ Cavity Location and Active Area” map. However, it is very hard to find a nest on our trees, which seems to be consistent with the result by other researchers as mentioned above. We remember during the winter time, there was one nest possibly on C3, as it is getting warm, the nest is gone. But the cavity is definitely a proof of how the squirrels are playing around and actually try to live in these oak trees, just like this photo is showing here on our tree C3:


How far can squirrels travel?

According to a test by United Exterminating Company to trap and track the squirrels through both using straight-line runs and zig-zag patterns to different areas and spray paint to mark them, it turns out:1- 2miles: squirrels don’t have any trouble getting back

1- 2miles: squirrels don’t have any trouble getting back

5-7 miles (with zig-zag pattern): returns were rare, 1 out of 15-20.

10-12 miles: Occasionally, there were squirrels returning back, but less than a half-dozen times

25 miles: only one surprising return

Conclusion: activity range is less than 5 mile. It is very rare for squirrels to go larger than 10 miles.

So the squirrels really can travel everywhere to search places to have fun and for food resources.

Squirrel Relocation Service


An interview with Michael E Beran, who is a Master Falconer at Wildlife Command Center, has provided some expertise and inspiration for our Squirrel Relocation Service to help squirrels find their new habitats after the pin oak trees are gone.

Pin oak trees are seasonal food resource for squirrels for a short period. Urban squirrels do not generally like to live in trees, but they also like to live in people’s houses and other built environment very well. They like to chase, run and fight with each other, so they are active all over the spaces, such as on the roof top and in the tree cavities.

Pin oaks are part of the habitat and they do provide a significant amount of food. Removing these habitats will definitely have impacts on squirrels’ life. However, taking them to an unfamiliar habitat is going to put them in danger, as they need to find food and water resources, and get themselves exposed to hawks, and other predators. More than 60% of relocated animals to unfamiliar habitats can’t survive. But, there are two potential options that can be done:

  1. Providing artificial habitat, such as squirrel boxes, to make them blend in the environment, the disadvantages would be the when squirrels do the bark stripping activities, these boxes won’t heal themselves like the trees do, so certain maintenance is needed.
  2. Providing other food resources, that could be sunflowers, apple trees, sweet potatoes or other oak trees. That needs another type of maintenance to keep those trees well to provide a supplementary good food resource. The disadvantage is that human intervention would also alter the squirrel generation.

From A Squirrel’s View – The Energetic Abruptness Protected by the Shades of Pin Oaks

squirrel view

According to the research published in Journal of Comparative Physiology A, gray squirrels (Sciurus carolinensis) can differentiate green, red with other colors but not able to distinguish green with red. This symptom is called dichromatic color vision. (Reference: Are Squirrels Able to Enjoy the Changing Colors of the Fall?  C. Claiborne Ray, The New York Times)

That being said, the squirrels can not enjoy the fall colors of trees but can differentiate the trees with the environment. 

From our observation, the most active time for the gray squirrels around and on our pin oak trees are early morning (before 8 a.m.) and late afternoon (4-5 p.m.), when the sunlight is not that strong. On cloudy days, they will more likely to show up than very sunny days, which further proves their resistance to strong sunlight.

However, our pin oaks would prefer a full sun environment to grow, which means at least 6 hours of direct, unfiltered sun,  according to the tree guide by Arbor Day Foundation.

As we all know, the pin oaks can provide great sun shading, that blocks the sun for the gray squirrels. This is one of the reasons why these two are good friends in addition to the squirrels’ needs of collecting acorns from the trees.

Tree Public Art in Rotterdam

tree public art

Along the canal in Rotterdam, there are many public artworks. This one particularly about one tree definitely stands out, as it seems trying to tell us a story about the tree’s past by preserving it through support by its other fellows in other species.

I thought this could be a great inspiration for our potential public artwork about one tree, that the story behind a tree does not need to only about its current life, but its memory is also worthy to discover.


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