Essay: Tree Rats, Jaybirds, and Oak Forests

Hands down the most visible animal with fur at Congaree is the ordinary gray squirrel or the rather unglamorous “tree rat” as we called them growing up.  Despite their unrat-like appearance squirrels are basically an arboreal rat and a member in good standing of the Order Rodentia.

Sciurus carolinensis, the “shade-tail of Carolina,” should be America’s national mammal – and the state mammal of more than 30 states where it occurs. They are such a part of our lives that we almost think of them as family pets. My yard in Columbia is full of them, with a record tally of eleven at one time on a half-acre lot. In wildlife management they taught us that a healthy squirrel population in the wild consists of about one squirrel per acre. One spring afternoon I counted sixty-four at USC’s Horseshoe, which probably comes out to about twenty squirrels per acre.

Unlike their city cousins, Congaree squirrels are the real deal – they are still wild animals. They have to spend much of their day searching for food and be on constant vigil for predators. You don’t have to worry about one jumping on your lap when you sit on a boardwalk bench to eat lunch. And speaking of park benches, years ago my friend Heyward Douglass and I were having lunch on a warm day at the State House grounds. It didn’t take long for the squirrel beggars to show themselves. Heyward finished his apple and handed the core to one persistent squirrel, who proceeded to consume it by twirling it around in its paws like corn on the cob. We noticed there were a few droplets of apple juice left on the squirrel’s whiskers. It dropped what was left of the apple core, and moved into a flower bed next to our bench that was full of dried, brown, hardwood leaves. The squirrel then moved slowly over the bed of dried leaves, stopping to pat the leaves every second or two with its front feet. It was odd behavior, and we were trying to figure out what the squirrel was doing. Finally the squirrel stopped and picked up a leaf and proceeded to wipe the apple juice droplets from its whiskers! We decided that the squirrel was looking for a soft dead leaf, one that would make a better napkin than the majority of the hardened and brittle dead leaves. Needless to say we both looked at each other and said, “Did you see that?”  It only highlights for me the amazing behavior of these ordinary, but at the same time, extraordinary, animals.

Congaree’s magnificent oak forest. How many are planted by squirrels?

I’m not sure what the squirrel density at Congaree is but probably close to the ideal of one per acre. There are plenty of natural foods, especially acorns in the fall and winter, and just as importantly, plenty of snags and hollow trees for nesting and roosting cavities. In the second- and third-growth forests of today, hollow trees and snags are rare, and squirrels build mostly leaf nests. Tree cavities, however, offer superior protection from the elements and predators.

If there is one thing lacking at Congaree in the squirrel’s favor, it is hickory trees (however, this deficiency is partially offset by an abundance of acorn-yielding oak trees). Hickory nuts are probably the gray squirrel’s favorite food; the sweet meat, high in fat, is equivalent to a steak dinner for the rodents. There are of course many water hickories in the park, and a fair number of bitternut hickories, but their bitter flavor puts them low on the squirrel’s menu. The shagbark hickory is the third type of hickory found at Congaree, but it is uncommon and grows more as single, isolated specimens than in stands. Its nut meat, surrounded by a thick husk, is sweet and more to the squirrels liking.

Squirrels spend a good bit of time on the ground at Congaree, especially in fall and winter, when they are busy caching acorns in the ground and later digging them up. Technically speaking, the squirrel’s nut-storing behavior for future use is termed “scatter hoarding” as opposed to a centrally-located “larder hoard.”  They use their keen sense of smell to locate the buried acorns when they get hungry. Squirrels, like blue jays and a few other acorn hoarders, are responsible in part for the spread of oak forests because they never find all of the nuts they bury. Squirrels, however, only cache their acorns a relatively short distance from the parent tree. It’s the blue jay that should get most of the credit as the Johnny Appleseed of oak forests since they may carry them up to a mile or more from the tree where they got them. Acorns are a mainstay in the fall and winter diet of blue jays. They prefer the smaller acorns of the red oak group such as laurel oak, water oak, willow oak, pin oak, and others.

Acorns are a favorite food of squirrels, blue jays, red-headed woodpeckers and many other species.

Blue jays have had a PR problem dating back to the country’s early settlement. They often go about in noisy gangs for much of the year and raid pecan and fruit orchards. Audubon painted them as egg thieves gorging on the yolk of what appear to be purloined mourning dove eggs. Jays are also not above taking baby birds for food. In my BB-gun youth we were told to shoot only starlings, English sparrows, and jay birds. I don’t remember ever having shot a wary jay, but we did rob a few of their nests for our egg collections.

Although blue jays are guilty of some of their crimes, they are not quite the thugs they have been made out to be. They are intelligent and interesting to watch and quite beautiful.  But it is for their close association with oak forests and acorns that blue jays deserve a statue in some town square. In a relationship that could almost be described as “mutualism,” where both bird and tree benefit, blue jays are considered one of the primary agents for the spread of oak forests, especially in the Midwest.

With blue jays and oak trees so important to one another, it has always been a puzzle to me why jays are so uncommon in the Congaree. The fall of 2013, for example, was a banner year for laurel oak acorn production, yet you could have walked all day through beautiful stands of laurel oak trees full of acorns and never seen a jay. What you would have seen, and heard, were dozens of another acorn predator, the red-headed woodpecker, quarreling over and defending their acorn larders from other red-heads. Red-heads also cache acorns, but they do so in the crevices and cracks of trees and not in the ground, where it would do the tree any good.

As close as it gets to the real thing – blue jay feathers courtesy of John Grego.

The two species would definitely be acorn competitors. Blue jays are no shrinking violets, however, and could handle themselves against aggressive red-headed woodpeckers. The lack of blue jays in Congaree is all the more mysterious since they are fairly common residents in bottomland hardwood forests of the Mississippi Delta (and where they caused a good bit of confusion during the hunt for Ivory-billed Woodpeckers since they were found to make calls that sounded like the woodpeckers).

Aside from their ecological contributions to oak forests, jays and squirrels have other things in common. They have lots of personality and interesting behaviors, are abundant and easy to watch, and are quite attractive. Although I miss blue jays at Congaree, I am convinced that there is a Ph.D. dissertation or two on squirrel behavior and ecology at the park, all done without ever having to leave the boardwalk.