The big, burly fox squirrel is said to be declining, while the little gray squirrel increases. One possible reason is that the big guy needs richer food sources. We've wondered if the fox would increase and the gray decrease as Somme's habitats improve. So far that isn't happening.
The gray squirrel is originally a creature of forest; the fox squirrel's classic habitats are oak savannas and open woodlands.
Fox squirrel - tough but vulnerable
We see fox squirrels at Somme from time to time - never more than one or two. This year, I can’t remember seeing a fox squirrel all summer. On October 7, while monitoring birds, I saw two. As for gray squirrels, though I didn’t count, I’m sure I saw at least thirty.
What's going on? Perhaps there are clues in Wikipedia and other easily accessible literature:
Fox squirrels are most abundant in open forest stands with little understory vegetation [apparently referring to shrubs]. The size and spacing of trees is among the important features of fox squirrel habitat. Fox squirrels are often observed foraging on the ground several hundred meters from the nearest trees.
What do they mean by “little understory”?
Optimum tree canopy closure for fox squirrels is from 20% to 60%. Optimum conditions of understory closure occur when the shrub-crown closure is 30% or less.
So far so good. Somme has a great deal of low-shrub, open woodland habitat. Red-headed woodpeckers also like such a habitat, and now breeding pairs are widespread and regular at Somme (at least five pairs this year). Is there something else missing for fox squirrels?
Fox squirrels in Ohio are said to prefer hickory nuts, acorns, and black walnuts ... and to be absent where two of these nut-producing trees are missing.
In Michigan, fox squirrels feed on a variety of foods throughout the year. Spring foods are mainly tree buds and flowers, insects, bird eggs, and seeds of red maple, silver maple, and elms. Summer foods include a variety of berries, plum and cherry pits, fruits of basswood, fruits of box elder, black oak acorns, hickory nuts, seeds of sugar and black maple, grains, insects, and unripe corn. Autumn foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts, and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter.
We have good quantities of most of the above, including maples and elms, although we're working to reduce the former and the later die of Dutch elm disease.
Juveniles usually disperse in September or October, so perhaps the occasional fox squirrels we see at Somme are dispersing from successful breeding habitat elsewhere. But where? And what do those places have that Somme does not?
One mixed-message fact about fox squirrels is that they do well in some suburban neighborhoods. Human preferred landscapes often have the scattered trees and open understory that the fox squirrels need. Gray squirrels have adapted to the urban too of course.
In a U. of I. study initiated in 1997 by Wendy Jackson and Joel Brown, citizen-science reports have indicated that:
Fox squirrels were more likely to be observed in the western and especially southwestern suburbs. There were 27 zip codes where only gray squirrels were recorded, compared to only two zip codes where only fox squirrels were recorded (60104 in the village of Bellwood and 60402 in the village of Berwyn). There were 85 zip codes for which both fox and gray squirrels were recorded.
One significant finding of that study was that fox squirrel abundance was associated with high populations of domestic cats. The smaller gray squirrel is more susceptible to predation.
Our study provides support for the idea that fox and gray squirrel coexistence is facilitated by a trade-off between managing the cost of predation and foraging efficiency, gray squirrels out-competing fox squirrels in areas of high food and low predator (or pet) density.
Decreasing numbers of fox squirrels have made them a species of concern in the states of New York, North Carolina, South Carolina, and Alabama.
But this is Illinois. Since they're widespread in lots of suburban zip codes, should our conservation thinking just ignore fox squirrels? But many bird species (for example the red-headed woodpecker and the barn owl) were long considered common inhabitants of yards and farms … but later became conservation priorities when those habitats stopped working for them. Too much pesticide? Changing tastes in landscaping? In contrast to urban landscapes, survival in nature seems more secure for both the species and the ecosystem. And is it possible that the oak communities would benefit in various ways from the return of this classic species?
Ecosystems are difficult to study. The first ecological study of Somme Woods was in conducted in 1908. Then, after a long pause, dedicated researchers at the Sommes have made strides in the study of plant communities, rare plants, woodland breeding birds, seed banks, and much more. Creative approaches (both pure science and applied) are much needed to help with management questions that need answers now.
It's interesting to consider the status of fox squirrels of southeastern United States as described in this NatureServe report:
The greatest threat to fox squirrel populations is in the southeastern U.S., where distribution and abundance have been reduced by loss of mature forest habitat. The widely spaced trees typical of mature longleaf pine-turkey oak forest upon which populations in the southeastern U.S. depend favor the squirrel's large size, running proficiency, and tendency to escape along the ground. The very open, parklike forest stands resulting from frequent fires produce better crops of pine cones and mast. However, the longleaf pine ecosystem, which once comprised some 70 million hectares across the southeastern Coastal Plain, is today represented by only about 2% of its original range. Survival of the fox squirrel in the Southeast is intimately tied to the fortunes of this declining ecosystem.
Only 2%? That's low, but Illinois' surviving high-quality savannas comprise less than 1/100th of 1% of the original, and the more common degraded ones are losing health and sustainability fast.
They're relatively easy to study. Fox and gray squirrels - like humans - are unusual among mammals in being out and active in the daytime, much easier for citizen-scientists to observe than coyotes, foxes, deer, weasels, raccoons, and, for that matter, flying squirrels, which too are nocturnal. Can anyone help us understand whether more of their foxy handsomeness would be a good addition to the growing biodiversity of Somme's savannas and woodlands?
References
References
Study comparing gray and fox squirrels in the Chicago area:
The NatureServe report: https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.105485/Sciurus_niger
Acknowledgements
The opening photo is from our friend Michael Jeffords in Outdoor Illinois Journal.
Photo of fox squirrel eating a flower is from Welcome Wildlife.
Final photo is from Wikipedia, a good service that deserves our support.
Proofing and edits by Eriko Kojima.
The smaller gray is said to out-compete the fox squirrel. How does that work? Gray squirrels eat a lot of human garbage from what I've seen. I have not seen fox squirrels exploiting garbage cans, but I have not lived where the fox squirrels are around.
ReplyDeleteThe really interesting squirrel to me is Franklin's ground squirrel. That threatened species is very rare in Illinois. It would be great if the Franklin's showed up in Somme.
Acorns are important but they need them every year, not every other year, or something else like hickory. Gray squirrels are better at hanging from the end of branches to snag samaras and seeds of elm, ash, maple. Fox squirrels tend to be more aggressive. It would be great to see a citizen science network for these squirrels.
ReplyDeleteTo quote from WTTW’s program “Urban Nature: The Great Squirrel Mystery| Chicago”
ReplyDelete“Project Squirrel data has indicated that Chicago-area fox squirrels prefer to set up their digs in more “dangerous” environments: exurbs where predators like coyotes and hawks are present, and inner-city neighborhoods where outdoor cats and dogs are more common. Gray squirrels occupy “safer” areas, where there are fewer predators, and cats and dogs are kept inside. Fox squirrels are bold enough to manage the risk of predators, whereas gray squirrels are more skittish. But in the absence of predators, gray squirrels outcompete fox squirrels for food resources and nesting sites.”