Leafy Disturbances

Leaves: at this time of year the woody plants are bare of leaves, and last summer’s weather-beaten foliage covers the forest floor in all directions. Is there anything we can learn about the lives of animals from this seemingly mute carpet? The answer is a resounding yes! In the photo below we see a well-used deer trail. The dry, undisturbed leaves on either side contrast with the darker, disturbed texture in the trail. Even when it’s compressed, deciduous leaf litter is harder to walk on than pre-existing trails, so deer often create runs between bedding and feeding areas.

It’s not as easy to detect deer tracks if they’re not on well used trails. The next photo shows an individual deer track, orientated toward the right. The hoof pressed down into the leaf litter and the outer rims left curved depressions on the top layer of leaves. But if you just were hiking along, would this print attract your attention? Probably not. To find individual deer prints it helps to study areas where the animals have spread out from obvious trails into feeding or bedding areas.

Fall is mating season for whitetail deer, and back then the males were spending most of their time trying to attract females. Bucks made scrapes on the ground and left their scent at the site by depositing urine in the scrape. They also left their olfactory signature by rubbing their foreheads and faces on overhanging branches. The signs of these mating rituals often last into spring. In the photo below (taken a few weeks ago) you can see a scrape just below an overhanging branch still bearing a few leaves.

A close-up of the scrape has a weathered look but still shows signs of deliberate disturbance.

Deer aren’t the only animals that clear leaves. Turkeys sweep leaves aside as they search for insects and other edible tidbits beneath the leaf litter. In the photo below debris lies on top of the leaves at the bottom and lower right, showing that the turkey stood facing the upper left as it tossed the leaves backward. By using both of its feet the bird created a roughly triangular cleared patch.

But turkey feeding scrapes aren’t always triangular. In the next photo you see one that’s more irregularly shaped. There can be a lot of variation in the shape of the cleared area and the amount of displaced debris.

Buck scrapes and turkey scrapes can be quite similar, but there are ways to tell them apart. First, deer mate exclusively in the fall, so buck scrapes discovered in the spring will show signs of several months of weathering. Turkeys make feeding scrapes in all seasons, so at this time of year they range from fresh to weathered in appearance. Both of the turkey scrapes shown above are relatively recent, while the buck scrape in the preceding photos had been created about five months earlier.

Another difference between deer and turkey scrapes is their distribution. An individual buck usually makes a limited number of scrapes, almost always associated with overhanging branches, in an area he is patrolling. Turkeys usually feed in groups, and they go wherever the eating is good, so turkey scrapes are likely to be more numerous and scattered more irregularly.

Squirrels also disturb leaves. The next image shows a cleared area at the base of a tree. When I found this I wondered if it was the result of frequent use as a take-off spot by squirrels.

To check, I looked at the bark above the cleared spot (shown in the next photo) and saw that the moss and outer bark had indeed been abraded. I’m attributing this to squirrels, the most common tree climbers, but I can’t entirely eliminate the possibility that it was a raccoon. Other climbing animals are unlikely because they are less likely to climb one tree repeatedly.

Like turkeys, squirrels search for buried nuts and insects, especially in the spring when stored food supplies may have run out. Both red and gray squirrels obtain these items by digging small holes. In the next photo you see a dig made by a squirrel. Debris from the hole can be seen below and to the right, so the squirrel must have been facing the upper left as it dug.

Here’s another image of a squirrel dig, this time in a layer of pine needles. If the buried object was a nut or acorn the hole usually retains a firm impression of the object. In the digs shown in both photos the bottoms of the holes were loose and irregularly shaped, so the food items were probably insects.

Deer also dig at leaf litter in search of nuts and acorns. White oak acorns are consumed by many animals and birds, so they disappear soon after they drop. The higher levels of tannins in red oak acorns make them less palatable, so they mostly lie uneaten on the ground until soaking rains leach the tannins out. But once they’re more digestible red oak acorns are sought out by many animals, including deer. Where red oaks are the predominant oak species, areas of churned up leaves like those in the next photo (taken last December) can be found in late fall and winter. You can see fragments of acorn shells and meats the deer dropped as they chewed.

If there’s a heavy, wet snowpack in late winter that compresses the leaves, deer feeding areas may be hard to recognize by the time spring arrives. But after winters with little snow like the one we just had, the signs are evident. A few weeks ago I went back to the area where the photo above was taken to see what it looked like. In the photograph below you can see that the leaves still lie loosely in piles and windrows. There aren’t any acorn fragments to be seen–if the deer weren’t interested enough to gather them up they would have been eaten by other animals like squirrels, mice, raccoons, crows, foxes, or even fishers. You’re not likely to find fresh evidence of deer foraging for acorns because the fall crop has been mostly consumed.

Areas where the leaves were not churned up by deer (or turkeys) look very different. Fall rains and the little snow we did have were enough to flatten autumn’s leaf fall into a smooth-looking mat like the one pictured below.

Some places cleared of leaves are more mysterious . Is this the work of a deer? Or a turkey? Actually, neither.

When you see the same spot in the more distant shot shown below, you’ll see what moved the leaves: water. The close-up above comes from the area in the lower left quadrant of the distance shot below. During a heavy rain, water flowed down the trail on the right and spilled over the edge into the leaves. As the water rushed downhill it made channels in the leaves and moved them into heaps along the edges.

Leaves have stories to tell, and to understand them we need to get familiar with undisturbed leaf litter. Once we begin to pay attention to leaves, and to places that depart from the unaltered baseline, we’ll have a whole new window into the lives of animals.

Squirrels Share Some Secrets

I’ve been getting more and more interested in squirrels. Like all animals, their lives are shaped by the seasons, and there’s much to discover if you can find and decipher the signs they leave. In late summer squirrels bite off oak twigs to get at the ripening acorns, and the “nip twigs”  (minus acorns) can be found scattered under oak trees. The acorn remnants–shell fragments and partly eaten acorn meats–may also be found on the ground or on nearby logs or stumps where a squirrel has a good view of its surroundings while feeding.

In September I found these apparently uneaten acorns, along with cap and shell fragments, scattered on the ground beneath some red oak trees. The acorns were intact, but every one was marred by brown spots. This puzzled me at first, so I got out my magnifier and took a closer look. I noticed that there were tiny tunnels in some of the brown spots, and one even had a minute, worm-like insect larvae. I also saw indistinct gouges in a few of the brown spots that looked a lot like tooth marks. Mystery solved! The squirrels were feeding on acorn weevils, often found inside acorns and much richer in calories than the acorns themselves.

We’ve had a very wet fall, and fungi have been popping up everywhere. I’ve been surprised to see how fond squirrels are of mushrooms. I’ve repeatedly come across mushrooms which had been plucked from where they had grown, carried to some other spot, and partly or almost completely eaten. Bite marks sometimes showed along the edges, and there were always discarded pieces scattered around–squirrels seem to be sloppy eaters. Slugs and snails also seem to love mushrooms, but they simply make broad, shallow gouges in the caps and the mushrooms remain standing where they grew.

When the weather turns colder squirrels give up their summer leaf nests and move into more sheltered lodgings, often in hollow trees. Instead of using leaves, they line their nests with fibrous material. The inner bark of this dead branch was stripped off by a squirrel and used to provide warm insulation for its nest. The smoothly denuded wood surfaces and hanging remnants are typical of squirrel work. In addition, there are usually a few gouges made by the animal’s incisors somewhere in the debarked area. Dead branches are the most common source of good nest lining material, but the bark of living honeysuckle and other shrubs is a favorite material where they are available.

You may have been wondering which squirrels I’ve been talking about. Actually, I’ve purposely avoided naming them because I’m often not sure. Our mixed forests host both red and gray squirrels, not to mention northern and southern flying squirrels, and it’s often difficult to know which species left a particular sign. I suspect that the oak nip twigs and the weevil feeding were done by gray squirrels, but red squirrels also feed on acorns. I’m pretty sure both red and gray squirrels eat mushrooms, and all of our squirrels line their winter nests with fibrous material. There are some types of sign–certain kinds of marking, and large middens under conifers–that can definitely be attributed to a particular species; more about those in future blogs. Until then, we’ll adopt the wise tracker’s attitude and recognize the limits of our certainty.