Words of Tracking: Common Walking Gaits

by Carl Strang

 

In an earlier set of posts (find under Methods category in sidebar to left) I introduced the alphabet of tracking, i.e., identification of the kind of animal that made the track. Today I want to take the next step toward reading the stories that footprints have to tell us. That is, to look at the basic gaits. A gait is a pattern of footprint placement, the building block from which an animal’s trail is built, and it also is the order in which the feet step as the animal moves. You will find the same gaits given different names in different references. I follow the terminology of my teachers at the Tom Brown school (link in left margin of the frame).

 

The pace gait is the usual traveling gait of certain animals, such as raccoons and bears, whose wide-bodied proportions favor swinging their weight from side to side, stepping with both left feet at once, then both right feet. If you try this, in a comfortable rather than lunging effort, you will find that your feet produce side by side pairs of footprints, left front foot beside right hind foot, right front foot beside left hind foot. Here is the pattern in a set of raccoon tracks.

 

Pace gait, raccoon

Pace gait, raccoon

 

 

The opposite of a wide body is a long skinny body, which we find in weasels. If your body is, to exaggerate, something like a rope with two little feet at each end, the easiest way for you to proceed will be to move both your front feet together, then both your hind feet, with the hind feet landing behind the front feet. This gait is called the bound. Often the feet are somewhat offset, an indication that the animal oriented its body axis at an angle rather than in line with its direction of travel.

 

Bound gait, mink

Bound gait, mink

 

 

Another gait in which the front feet move together and the hind feet move together is the gallop. This is common in rodents and rabbits, animals whose hind legs are more powerful than the front, so that the hind feet land in front of the front feet. Cottontails typically place one front foot in front of the other, while rodents such as mice and squirrels, as well as masked shrews, place their front feet side by side (in the photo the shrew is moving left to right).

 

Gallop gait, cottontail

Gallop gait, cottontail

 

Gallop gait, masked shrew

Gallop gait, masked shrew

 

 

There is one circumstance in which cottontails place their front feet side by side, however. I will leave this one for you to puzzle over. Look for examples this winter, see if you can figure it out. Here’s a photo so you know what to look for.

 

Cottontail gait puzzle

Cottontail gait puzzle

 

 

The final common walking gait is typical of hoofed animals (white-tailed deer in NE Illinois), the dog family and the cat family, as well as us (when do we walk on all fours?). This one is called the diagonal walk, and unlike the others the feet move separately in a sequence: left front, right hind, right front, left hind. In this case the left feet come down in close to the same place, and so do the right feet. The overall impression is a zigzag between right foot pairs and left foot pairs, hence the name for this gait.

 

Diagonal walk gait, wolf (Isle Royale)

Diagonal walk gait, wolf (Isle Royale)

 

 

There are other gaits, but they are less common or are special cases and will be reserved for later. Also, the connections I have made between animals and gaits are limited to routine travel. When circumstances require, animals shift out of their normal walking gait. For instance, a raccoon in an extreme hurry does not, cartoon like, do a real fast pace gait. Instead, it shifts into a gallop. Tracks outside the normal pattern are a clue that something unusual, therefore interesting, was happening.

Advertisements

Goose Roosts

by Carl Strang

 

I have completed my first sweep of DuPage County for Canada goose winter roosts. As I mentioned in an earlier post, the geese appear to use a hierarchy of sites. Early in the winter there are many locations where groups of geese spend the night. Some of these roosts, usually located on streams, are significantly larger than the others. As ponds and lakes freeze, geese abandon them. At the same time, the major sites where water stays open show an increase in numbers that suggests many of the geese shift from satellite sites to persistent ones. I know from past observations at Fullersburg, however, that even some of the major sites can freeze and be abandoned during severe cold periods. Geese return, however, when the water re-opens. Usually such extreme weather is limited to a week or two at most in a given winter.

 

fbw-canada-geese-1b

 

Here are the major DuPage roosts I know about so far, each of which holds several hundred to a few thousand birds. I would appreciate additions if readers know of others. All of the results at this point have to be regarded as tentative.

 

Deep Quarry Lake, West Branch Forest Preserve: north central DuPage

Redmond Reservoir, Bensenville: northeast DuPage

Fermilab, interior of accelerator circle: west central DuPage

Blackwell Forest Preserve (south): west central DuPage

McDowell Grove Forest Preserve: west central DuPage

Hidden Lake Forest Preserve: central DuPage

Fullersburg Woods Forest Preserve: east central DuPage

 

As of December 20, Deep Quarry Lake had frozen, and so at least was temporarily inactive. The Fermilab site was nearly frozen and down to 87 birds. At least the Blackwell, McDowell and Hidden Lake roosts still were active. This has been an unusually cold December.

 

cg-mcdowell-1b

 

Smaller roosts that may prove to be satellites, holding up to a few hundred birds:

Timber Ridge Forest Preserve: central DuPage

Hinsdale Lake: east central DuPage

Willow Lake west of Fox Valley Mall: southwest DuPage

East Branch DuPage River at 7 Bridges, Lisle: south central DuPage

 

At least the Timber Ridge roost was frozen and abandoned December 20. To some extent I believe the geese are scattering along open rivers, dividing into smaller groups. They are not necessarily all crowding into the larger roosts. Also, given the early arrival of severe winter weather, some geese may have decided to move south and leave the area entirely.

 

In January I will return to these roosts and see how they are faring.

Sketching Mayslake’s Trophic Structure

by Carl Strang

 

 

As I familiarize myself with an area, there are several big conceptual nets with which I try to comprehend that place. These lack fine detail, but provide first approximations that can be filled in as I learn more. One conceptual frame for an area is its general topography and drainage pattern. Another is the general human history and influence on the land. A third is the mosaic of vegetation communities. A fourth is the geology. Today I want to focus on yet another frame, the trophic structure. This is a broad-brush first stage in constructing a food web. The trophic levels of an ecosystem are the steps through which energy “flows” (the quotes are a field ecologist’s recognition that abstract food pyramid diagrams, and the arrows that connect food web elements on the page, cover up a certain amount of desperate flight-and-chase, crunching, and screaming. All our lives continue at a cost, but I digress).

 

In earlier posts I have documented some of Mayslake’s animal life. The top predators mentioned already include coyotes and mink. A day seldom goes by without me seeing a red-tailed hawk or two. I also have seen tracks of great horned owls, and the Mayslake staff have observed these birds at that preserve for years.

 

Great horned owl tracks, Mayslake

Great horned owl tracks, Mayslake

 

 

Note that in this photo, the great horned owl tracks are farther apart than in the photo I took on the Christmas bird count. This is the more typical spacing, but again there is that odd asymmetry in the toes.

 

 

Mayslake’s part-time predators include raccoons and skunks, among others.

 

Skunk tracks (far right), Mayslake

Skunk tracks (far right), Mayslake

 

On a smaller scale, I have seen tracks of short-tailed and masked shrews, which are predators of small animals including invertebrates but also mice.

 

Common plant-eating animals at Mayslake include deer, mice, voles, squirrels, chipmunks and cottontail rabbits. There are also the wandering winter birds eating seeds (as in the paper birch account).

 

Rabbit trail, Mayslake

Rabbit trail, Mayslake

 

 

Over 50 kinds of trees, shrubs and vines, along with uncounted herbaceous plants, are the preserve’s primary producers, solar energy harvesters that form the foundation for the whole trophic shebang. In the warm months, each kind of plant hosts several insect consumers that in turn are food for predators including an influx of migrant nesting birds.

 

And let’s not forget the scavengers. Some of the animals listed already, the coyote and skunk for instance, along with opossums such as the young one whose tracks I saw in the southern part of the preserve recently, are happy to clean up the odd dead carcass they encounter.

 

Mayslake is not a huge property as forest preserves go, but it’s big enough and diverse enough in vegetative structure to support a complex community for which I have here provided only the broadest of introductory sketches. More detail to come.

Merry Christmas!

by Carl Strang

 

A safe and happy Solstice season to you and yours.

 

 

[

Caribou calf (New World reindeer equivalent and probable DuPage County resident 15,000 years ago), Newfoundland

Caribou calf (New World reindeer equivalent and probable DuPage County resident 15,000 years ago), Newfoundland

]

 

 

 

CBC Part 2

By Carl Strang

 

Yesterday I outlined the story of a shared day with other birders in the Christmas Bird Count. Today I am finishing with some of the birds we were especially happy to find, species we certainly don’t see every winter day.

 

One of these species was the purple finch. We saw both males

 

cbc-purple-finch-male-b

 

and female-plumaged individuals, some of which may have been first-year males.

 

cbc-purple-finch-female-b1

 

The single most unusual bird of the day was this rusty blackbird.

 

cbc-rusty-1b

 

Its head showed the sharply contrasting rusty tones of winter plumage that give the species its name, but this male appeared to be delayed in its body feather molt.

 

cbc-rusty-2b

 

A final species of special interest was the eastern bluebird. We saw two small groups of them, one along the Prairie Path containing this female.

 

cbc-bluebird-female-or-young-b

 

The second group was at Kline Creek Farm, and included this hackberry-loving male.

 

cbc-bluebird-male-2b

CBC Part 1

by Carl Strang

 

Yesterday was the Fermilab Christmas Bird Count, in which I have participated for several years now. It’s an opportunity for birders to join in a continent-wide effort to compile an annual snapshot of bird numbers and geography. Other groups cover other areas at other times, generally in the second half of December or early in January.

 

Each count circle is divided into areas, 8 in the circle centered on the Fermilab grounds. Here are the other members of our Area 4 group from yesterday, left to right in the photo: Judy Morgan, Linda and Frank Padera, Chuck Drake, Marcia and Lee Nye, and group leader Urs Geiser.

 

cbc-birders-b

 

Our day began very early, with most of the morning devoted to covering a 4-mile stretch of Prairie Path northwest from the intersection of County Farm and Geneva Roads. If the birds were competing to be counted, on this day the starlings jumped to an early lead with this tightly packed mob on the wire, and never looked back.

 

cbc-starlings-b

 

As you might expect, most of the birds we see are of the more common or familiar species, like this white-breasted nuthatch.

 

cbc-nuthatch-b

 

The icy snowfall of a couple days ago made walking more of an effort than in many years, but did add to the beauty of the scenery.

 

cbc-stream-scene-b

 

While birds that were moving and calling were easy to find, others held still and required a little more effort, like this mourning dove.

 

cbc-modo-b

 

We encountered great horned owl tracks in the snow.

 

cbc-gho-tracks-b

 

The night before, the owl had killed a cottontail rabbit.

 

cbc-rabbit-predation-by-gho-b

 

Tracks don’t count, however, so we could not include the owl on the day’s list. We also saw a coyote, and passed where it or another had caught a mouse or vole beside the trail.

 

cbc-mouse-predation-by-coyote-b

 

The day’s tally included several red-bellied woodpeckers,

 

cbc-redbelly-b

 

as well as downy woodpeckers.

 

cbc-downy-1b

 

In the afternoon we explored additional sites, such as Kline Creek Farm (cattle also don’t make the list, nor did we find any cowbirds).

 

cbc-kcf-cattle-b

 

Tomorrow I’ll share some of the birds that were unusual enough to get us especially excited.

New Damselflies

by Carl Strang

 

I encountered two damselfly species this year I never had seen before. One of these, the emerald spreadwing, was at the Morton Arboretum. I didn’t get a photo, as I still was learning how to maneuver with a broken clavicle and rib. The marsh habitat was different from my regular monitoring routes, and so this species could well be more common than might be suggested by my having gone for years without seeing one. The little spreadwing was beautiful, though, its body a metallic green color.

 

Somewhat more surprising was the second damselfly, as I found it at the end of my third season at Fullersburg Woods. I did not recognize the insect, but on that cool October 1 had no trouble approaching and photographing it.

 

smoky-rubyspot-5b

 

It proved to be a female smoky rubyspot, a close relative of the ebony jewelwing and American rubyspot, two common, large damselflies of DuPage County streams. The species is uncommon, but certainly not unknown in northeast Illinois. Does it generally occur in parts of Salt Creek not visible from trails? Is it just plain rare on that preserve? Finding it, as well as the Cyrano darner and fawn darner mentioned in an earlier post, demonstrated that I need more experience with the dragonflies and damselflies of streams, so I plan to put in some kayak time next year looking for them at two or three sections of rivers in DuPage County.

Tricky Tracks

by Carl Strang

 

OK, it’s quiz time. In fairness I should begin by saying this is not a straightforward quiz, but rather I will present you with some examples of marks in the snow that I have encountered in recent days that are not clear and easy to identify. I won’t even guarantee that familiarity with the tracking ID primers (find under Methods category in sidebar to left) I posted a few days ago will be any help. All photos are from Mayslake Forest Preserve.

 

Here’s the first. I will show you the answer below, but please take at least a moment to study the image first.

 

leaf-track-2b

 

Now here’s the second. Again, the answer will be revealed below.

 

puzzle-track-1b

 

In the meantime, I want to share one that had me going for several minutes. I found this trail near the chapel. A small animal had come out into the open from the trees, then looped back.

 

puzzle-mouse-2b

 

The tracks were really peculiar, as though the critter were carrying a stick in its mouth that impressed the snow regularly.

 

puzzle-mouse-3b

 

I finally concluded that these were the tracks of a white-footed mouse. The “stick” mark was made by its tail. For some reason that I still cannot figure out, the mouse was hopping sideways, so that its tail went into the snow off to the side of the animal’s direction of travel.

 

puzzle-mouse-4b

 

OK, here’s the answer to the first puzzler:

 

leaf-track-1b

 

The lesson from this is that not all marks are made by animals. The leaf had been blown across the snow by the wind. For the second, I provide a photo of the same footprint taken at a slight angle rather than straight down.

 

puzzle-track-2b

 

This is a dog track. Dogs often put the main part of their weight in their middle two toes, sometimes to the extent that the outer toes don’t register very well. When the toenail mark merges with the toe, this can result in a footprint that at first glance is close to a deer track.

 

I hope this was fun. I’ll provide other puzzlers from time to time.

Fullersburg’s Abandoned CCC Trail

by Carl Strang

 

Yesterday I introduced the Civilian Conservation Corps chapter in the history of Fullersburg Woods Forest Preserve. Today I want to describe an abandoned CCC trail that awaits exploration by the adventurous.

 

fullersburg-1937-map-ccc-trail

 

The area is on the north side of Salt Creek in the western part of the preserve. Except for a narrow strip of land along the stream bank, and the low triangular area downstream from the Rainbow Bridge (the bridge at the western extremity of the preserve), the north side of Salt Creek still was in private hands in the days of the CCC. They apparently dealt with the challenges posed by this low area of flood plain by piling fill, installing concrete culverts, and cutting into the side of the hill (reinforcing above and below with walls of dolomite slabs) to build a two-branched trail.

 

fbw-structure-8c-ccc-trail

 

That trail now is so overgrown that navigating it provides something of a challenge, but is easier in winter with vegetation down. The trail does not exactly follow the route indicated on the 1937 map. Walking east from Rainbow Bridge, and looking to the right shortly before today’s trail begins to climb the steep hill (the Tinley Moraine), you can see the old elevated trail route punctuated by a concrete culvert.

 

fbw-culvert-1-b

 

That elevated fill is well populated with honeysuckle now, but if you follow it you will find it curves left and soon reaches the edge of Salt Creek. The trail there goes along the edge of the creek in both directions, completely outlining the creek edge of that low piece of ground. Following it east (left) you will cross another concrete culvert,

 

fbw-culvert-2-b

 

and eventually reach where the abandoned trail climbs up to rejoin today’s trail. As you do, keeping an eye out for poison ivy and stumbling over the trunks of fallen trees, you will note the stacked dolomite wall that reinforced the stream bank to your right,

 

fbw-structure-8h-trail-edge-b

 

and the similar retaining wall built into the hillside to your left.

 

fbw-structure-8e-retaining-wall

 

If you accept this challenge, you will be training your eye to detect old human changes to the landscape. That experience will improve your ability to detect such influences in other places you may choose to explore.

Fullersburg Archeology: Trail Shelters

by Carl Strang

 

Fullersburg Woods Forest Preserve was the site of Civilian Conservation Corps camp #V-1668 in the 1930’s. In 1933, in response to the economic calamity of the Great Depression, Franklin Delano Roosevelt started the CCC in the first two months of his presidency. By the end of that year, two camps had been established on forest preserves in DuPage County, at McDowell and Fullersburg. Young (late teens to early twenties) single men moved into the camps, enrolled for 6 months at a time and could extend to 2 years. The camps were run by the army, but the work was directed by foresters and other specialists. At Fullersburg the camp was located at the present Hilltop Prairie. In 1937, the year before the Fullersburg camp closed, a map was prepared that shows a number of structures that had been built or were under construction.

 

fullersburg-1937-map-a

 

The CCC built the Visitor Center and other buildings I will highlight in some future posting. Today I want to focus on a series of structures, labeled “Trail Shelters” on the 1937 map and represented there by little black rectangles, that no longer stand.

 

fullersburg-1937-map-ne-a

 

They are not entirely gone, however. Guided by the map, I went to these locations to see if any traces of the shelters remained. In a couple cases I found lines of dolomite blocks in Salt Creek along its edge, right where the shelters are marked on the map. Apparently the dolomite pieces, a common construction material used by the CCC, were the floors of the small shelters and have collapsed into the creek.

 

fbw-structure-26-2b-rocks-in-creek

 

In one case more remains. This one, across from the northeast corner of Willow Island, still is well represented by its relatively intact dolomite stream bank foundation, and a concrete post support at one end. You have to pick your way through the woods off trail to find it.

 

fbw-structure-23-concrete-end-b

 

These rocks, quarried at Lemont, transported to Fullersburg, forming part of structures for a time and now scattered, remain to speak to us of the preserve’s history. They also add structure and chemistry to the microenvironments where they now sit, serving as shelter or obstacles to small animals. From the standpoint of the stones their present locations still are fresh and new compared to the hundreds of millions of years of their existence.

« Older entries

%d bloggers like this: