Reading an Old Story

by Carl Strang

The landscape is a book of many chapters, waiting to be read. Some chapters are fleeting, and must be read within days of their writing (before the snow melts). Others last for years. Near the south shore of Mays’ Lake at Mayslake Forest Preserve there is a decaying tree stump.

The stump is on the right, with a stem of similar color and diameter beside it. Both have lost their bark.

The stump is on the right, with a stem of similar color and diameter beside it. Both have lost their bark.

A closer examination reveals the tooth marks of a beaver on the ends of both pieces. Looking up, we find that the stem leads to branches tangled in those of adjacent trees.

No bark remains anywhere. This has been here for years.

No bark remains anywhere. This has been here for years.

This view best shows how the tree's fall was arrested.

This view best shows how the tree’s fall was arrested.

Cutting this tree probably was a full night’s work or more. All the beaver obtained was the cambium it could reach from the ground. We got a chapter to read, all the more valuable because there have been no beavers resident on this lake for at least 5 years.

The Flood and Animals

by Carl Strang

Yesterday I shared some images of last week’s flood at Mayslake Forest Preserve. When I saw how high the water had risen, I expected to find the Canada goose nest washed out. She was in the bowl-like parking lot marsh, on top of a muskrat house. When I got there I found that the water was high, but it had found a new outlet that limited its rise.

The water came within a few inches of the nest, but did not flood it.

The water came within a few inches of the nest, but did not flood it.

As I walked the east shore of Mays’ Lake that day, I heard a sudden loud splash above the roar of the nearby stream. It reminded me of a beaver’s warning dive, but there have been no resident beavers on the preserve in some years, so I passed it off as something else. On the next day, however, I found this:

A beaver had been there indeed. The freshly gnawed cuts showed the wide grooves made by beaver incisor teeth.

A beaver had been there indeed. The freshly gnawed cuts showed the wide grooves made by beaver incisor teeth.

Until I have reason to believe otherwise, I imagine this beaver was passing through, following the course of the flood or perhaps using the elevated waters to make an exploratory trip.

A final image comes from the day after the flood, as a northern rough-winged swallow rested at the edge of the lake.

A number of rough-wings, tree and barn swallows were foraging close above the water’s surface.

A number of rough-wings, tree and barn swallows were foraging close above the water’s surface.

This was a reminder that the spring migration is accelerating as the end of April approaches.

Beaver Species Dossier

by Carl Strang

The species dossier idea came from my realization in the 1980’s that much of what I “knew” about wildlife came from the scientific and popular literature rather than personal experience. I went species by species, writing what I could remember about each one from memories of my own observations. Then I built the dossiers with added notes. The dossier begins with the initial paragraphs, followed by notes dated by a code that uses two-letter combinations to signify months.


Beaver, Salt Creek at Fullersburg Woods

This aquatic rodent lives in ditches, rivers, and lakes. Observations to date have been in the Culver, Indiana, area (Maxinkuckee, Tippecanoe, Yellow River, Fish Hatchery), southern Ontario, and DuPage County, Illinois. The signs are seen much more often than the animals themselves; they are crepuscular/nocturnal for the most part, although the Canadian ones occasionally appeared in daytime, and I have seen them during the day in northern Lake Michigan and the West Branch of the DuPage River (mid-winter). Alarm signal: dives noisily, augmenting the splash with its flat tail.

Stand-alone lodge, Canada

They feed on bark and twigs of willow and other woody plants, storing large underwater piles of branches in fall for winter use. They also stripped bark from the 1-4″ diameter X 1-3′ long sticks used in building dams and lodges. The den can be in a bank or in a stand-alone built lodge. Bank dens are used in larger, deeper rivers and lakes, although built lodges also can be seen in such places. I have seen built lodges in Canada, Lake Maxinkuckee (Venetian Village), DuPage Co. (e.g., Churchill F.P.), Isle Royale. They have a distinctive appearance because of the white sticks, though some lodges on riverbanks are not rounded and so at first glance resemble piles of drift from the last flood. Mud also is used in construction. Lodges have been 8-15′ in diameter, 2-4′ high, usually on a bank.

Beaver dam, Tri-County State Park

Small streams may be dammed to create a pool (the most ambitious dam I’ve seen was on the West Branch of the DuPage River at Blackwell in mid-winter). Dams, like lodge coverings, are built of stripped sticks, mud, vegetation, usually have a slight U-shaped bend pointing downstream, and are not particularly high above the contained water level, though some on Isle Royale were taller than me on the downstream side. Very long dams can have a more sinuous shape; I’ve seen them more than 50′ long.

High beaver dam with trail, Canada

Beavers will carry branches from other bodies of water to the home pool. Cut trees are distinctive with large tooth marks and pointed (cone-shaped) ends. Beaver tracks are large, and have the rodent formula (4 toes front, 5 back), the webs of the hind feet not always making noticeable marks.

Beaver front footprint

31AU86. Beavers at Culver’s fish hatchery have reinforced the base of their dam with a heavy plastering of marl.

18DE86. Month-old beaver sign, Willowbrook Back 40: several black cherry trees had their bark chewed off on the stream side of the trunk. No others in the vicinity (willow, box elder) were damaged.

11JA87. At the mouth of Sawmill Creek, Waterfall Glen F.P., beavers this morning fed on bark of a box elder 7″ dbh, they had cut down earlier. They had made a trenchlike single path in 6″ snow between stream and trunk.

8MR87. 2 ash trees 8″dbh cut down but only some bark removed from trunk. Otherwise untouched, for months.

Beaver-felled tree, Fullersburg

28MR87. Beavers at Waterfall Glen cut three 8″ dbh bur oaks, ate much of the bark from 2 of them, in an area with much willow.

23JA88. McDowell F.P. Beavers built a long winding dam on Ferry Creek, 20-30 yards long

15MR90. McDowell. Beavers were active in the evening dark during my night hike program. We heard one chewing: identical to the sound of a squirrel gnawing a nut, and as rapid, but much louder. Several of us shined lights on it. It was on the opposite side of the river, standing up on its hind feet, against the tree. After at least 30 seconds of being illuminated, it abruptly ran into the river. It swam for another 20-30 seconds, still in lights, then walked up the bank back to the same tree, and resumed gnawing. The alarm splash is like a big rock being thrown in. I didn’t detect a tail slapping component.

13NO99. A beaver dam has been built across the very low West Branch of the DuPage River, Elsen’s Hill at the eastern horse ford.

29MR00. While running past the borrow pit at McDowell Grove Forest Preserve, I frightened a beaver into the water. It swam under the surface for 20 feet or so, a stream of bubbles revealing its position, then surfaced. Immediately it dove again, but as it did so I saw it deliberately lift its tail and slap it on the water. I could detect the sound of it, but the splash made by the posterior part of the body (spread feet?) was the louder sound. Perhaps the double sound makes it a communication for beavers, to distinguish it from other splashes.

11MR01. A beaver lodge is on the shore of the old gravel pit on Timber Ridge Forest Preserve (at the intersection of County Farm and Geneva Roads). There has been much recent gnawing of nearby woody plants.

8AP01. At around 8:30 a.m. at Red Oak Nature Center I heard a gnawing sound down near the edge of the Fox River. It was a beaver, sitting in the shallow water and feeding on the twigs of a shrub or small tree overhanging the river (intervening brush too thick to get an ID of the plant). The beaver was reaching up, biting off a branch, then consuming the twig. Less than about 3/16″ in diameter, the twig was consumed by the beaver holding it like a piece of stick candy and nibbling on it with gnawing sounds reminiscent of a squirrel working on a nut but more rapid. After 2-3 seconds of biting off the end, the beaver chewed with its molars for a few seconds, swallowed, then worked on the end some more. When the diameter of the remaining twig became greater, approaching 1/4″, the beaver turned it sideways (always holding it in the front feet) and quickly stripped off the bark.

22OC01. Beavers have been very busy in recent days at the marsh beside South Blackwell’s Heron Trail (marsh full of water thanks to heavy rains in recent weeks). They have trampled a path through the cattails all the way to Heron Trail, and have been cutting the small willows and cottonwoods into pieces, eating the bark from some of the bigger chunks, and hauling the tops into the water (drag marks visible in the mud).

6JL07. Fullersburg. A beaver swimming up the main channel along Sycamore Peninsula went to the shore at 8:30 a.m. and ate some root bark and twig bark from American elms. It continued upstream past the Visitor Center.

Spring Time

by Carl Strang

It’s spring, and it’s time, time to shift into the new season. There are signs in abundance.

Downy woodpeckers have been getting feisty.

On Tuesday I saw Mayslake Forest Preserve’s first butterfly of the season.

An eastern comma, one of the butterflies that hibernate in the adult form.

Yesterday I set out the amphibian traps in the stream corridor marsh. It seems doubtful there are any salamanders to catch, but other interesting things turned up last season, and I’m willing to try again.

It’s important to make sure part of the trap is out of the water, for the benefit of air breathers that may get caught.

I also have begun to break out of my routine preserve monitoring routes. I am sure that after 3 years I am getting diminishing returns from them. Yesterday provided a case in point.

I have walked the trail past this big cottonwood (40 inches in diameter) many times, but yesterday I made my way through the brush on its backside, and saw this scar.

A close look revealed an interesting story.

Years ago, beavers had the ambition of chewing down the big tree. Their gnawing girdled it half way around before they gave up, or left.

In the first of the two photos you can see how large the area is where the tree has grown back over the scar. This is the largest such overgrowth I have seen, apart from lightning scars. Those are not as deep as this, however. This is a good example of how much of this preserve’s story I still have to learn.

Prehistoric Life 18

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Pliocene Epoch (5.2-1.64 million years ago)

The Pliocene Epoch, literally “more recent,” originally was defined (1833) by the percentage of then known fossil mollusk species still living (35-95%). Its end is marked by the beginning of the glacial times.

Life on Earth. In the Pliocene, grazers became largely supplanted by more generalist herbivores as savannas became widespread in Eurasia and North America. The dominant groups were camels, antilocaprids (e.g., pronghorn “antelope”), and Equus horses (which, like most horses, originated in North America). Opossums diversified in South America, mammoths appeared in Africa (early Pliocene), the North American rhinoceroses vanished (middle Pliocene), and Sorex shrews appeared in the late Pliocene.

Sorex shrews like our short-tailed shrew of today made their evolutionary appearance in the Pliocene Epoch.

Land bridges finally allowed camels to spread into South America and Asia in the Pliocene (a camel survived in North America into late Pleistocene times). In the middle Pliocene, continued connection to Asia brought immigration of more carnivores, deer, and the elephant Stegomastodon. From North America to Eurasia went a rabbit, a squirrel, the beaver, and Equus.

The world’s lynx and cheetahs first appeared in North America, crossing to the Old World via the Bering Sea land connection.

In the late Pliocene, new appearances were pocket gophers, the white-tailed deer genus Odocoileus, raccoons, the giant beaver, bobcat (Old World lynxes, and also cheetahs, trace their ancestry to the New World where their groups first appeared), the New World porcupine family, eastern mole, and masked shrew.

Modern deer made their appearance in the Pliocene.

In the meantime, the first hominids were beginning to walk upright in Africa 3.8-4 mya (million years ago; Science 307:1545). Upright walking may have begun in the trees, as a hand-assisted way of negotiating thin, flexible branches (Science 316:1328 ). “Lucy,” Australopithecus afarensis (3-3.6my ago), regarded as a human ancestor or close to it, has been tied to the older A. anamensis (4mya), which in turn may have come from the still older Ardipithecus ramidus (4.4mya). Fossils of all three species were found in the same African river valley (Science 312:178). Ardipithecus significantly was a woodland dweller; apparently upright walking was not a product of a grassland habitat (Science 326: 64). Genus Homo had evolved by the late Pliocene, with species from Africa to Asia. Homo habilis and H. erectus are two earlier species which apparently overlapped considerably in time, so that it is uncertain whether the latter descended from the former (Science 317:733). Examination of limb structure points to habilis being arboreal while erectus was terrestrial, so a connection by descent is unlikely (Science 320:609).

The New World chickadees evolved from a single species that emigrated from Eurasia in the Pliocene.

Birds also were dispersing, and our modern species began to emerge. At least some modern songbirds had evolved by the early Pliocene (Auk 124:85). The chickadees and titmice, which had appeared in Eurasia originally, came over to North America in the Pliocene. The first crested species (titmouse) came over around 4 mya, and a single non-crested (chickadee) founder species around 3.5 mya. Subsequent evolution led to the 3 modern titmouse species and about 7 chickadees in the Americas. One terror bird species, in genus Titanis, reached North America from South America 2-3 million years ago, but was extinct by the end of the Pliocene.

Local landscape. Cooling and increased seasonality continued in the Pliocene (the middle Pliocene was the last time that Earth temperatures were warmer than at present).  Climate in the early Pliocene was significantly warmer than today; the major difference apparently was that the El Niño pattern of Pacific Ocean currents was permanent rather than episodic as it is today. The re-establishment of such a pattern is a possible outcome of global warming (Science 312:1485). Woodlands were more open in the Pliocene, perhaps savanna-like in places in our area. Elsewhere in North America, the continent developed its first near-modern boreal forest, as well as the first deserts, tundra and permafrost areas.

The Pliocene brought increasing seasonality, and extensive savannas replaced much of the Miocene grasslands.

The nearest Pliocene deposits are tiny areas in southern Indiana, and extensive areas in eastern Nebraska. By the Pliocene, much of northeast Illinois was draining eastward into the river that ultimately was enlarged by Pleistocene glaciation to become Lake Michigan. This happened when the relatively erosion-resistant and eastward-sloping Niagaran dolomite beneath us was brought close to the surface. Today, surface waters are directed by much more recent glacial deposits on top of that bedrock, and all ultimately flow into the Des Plaines-Illinois River system, ending up in the Gulf of Mexico rather than the North Atlantic.

Local life.  There is a likelihood that the camels, antilocaprids and horses (including Equus, the genus that includes modern horses) were represented locally. Deer, rabbits, beavers, raccoons, sabertooth cats (including Meganteron, an ancestor of the famous Smilodon), bears, the scavenging “hyaenoid dog” Borophagus, otters, and skunks are other likely species at that time.

Prehistoric Life 16

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Oligocene Epoch (35.4-23.3 million years before present)

The Oligocene Epoch (named in 1854), literally “little recent,” was divided from the Miocene of which it originally was part, based on fossils in Germany.

Life on Earth. The first grassland ecosystems appeared in Asia in the Oligocene, a profound step in the history to follow.

At the beginning of the Oligocene there was a big diversification of North American mammals, with only a quarter of the Eocene genera continuing. Change was slow for the rest of the epoch. This rapid change, preceded by a wave of extinctions, is associated with a time of climatic cooling. Relatively little is known about the Oligocene, because its general lack of change after the beginning has interested few researchers.

Those peculiar derived artiodactyls, the whales, continued their slow evolution through the Oligocene.

The oreodonts were a diverse North American artiodactyl (even-toed ungulate) group in the Oligocene; they declined to extinction at the end of the Miocene. The early Oligocene was the time when the browsing perissodactyl titanotheres (brontotheres) peaked in North America and Asia. Another perissodactyl, the giant rhinoceros Paraceratherium of Asia (also known as Indricotherium or Baluchitherium), is the largest known land mammal ever. It lived in the Oligocene and Miocene, was 18 feet high at the shoulder and could reach twigs and leaves 20 feet off the ground with its 5-foot-long head.

The ground sloths evolved in South America, the first ones appearing in the Oligocene fossil record.

Early in the Oligocene the first beavers appeared (in North America), the first procyonids (raccoon family) in North America and Europe, the first peccaries in North America. The Middle Oligocene brought the Canidae (dog family). Paleosciurus tree squirrels first appeared in the early Oligocene in Europe (Science 299:1568).

Peccaries, another artiodactyl group, evolved into existence in the North American Oligocene.

The hyaenodontids and nimravids became extinct in the late Oligocene, resulting in the “cat gap,” a lengthy period of time in which the North American carnivore fauna was dominated by larger canids and amphicyonids, and smaller mustelids (weasels), but nothing resembling a cat. The first ground sloths evolved in South America in the Oligocene.

Local landscape. A turning point in post-Cretaceous times was the separation of Australia from Antarctica in the late Eocene. The consequent establishment of a permanent cold current around the latter continent in the Oligocene brought a cooling to the global climate that impacts us to this day. Brief but intense glacial episodes, set off by changes in Earth orbital characteristics and made possible by the cold south polar currents, happened both at the beginning and end of the Oligocene (Science 314:1894). The cooling trend continued until our local climate became temperate in the Oligocene. Deciduous dry forests passed from semi-tropical to temperate.

Grassland ecosystems still were in North America’s future, but they had their start in the Oligocene, in Asia.

The oak family became more important both east and south of here. In the Plains to the west, hackberry was common, and that region may have been a low-rainfall scrubland (remember, no grasslands were here yet). The closest Oligocene deposits are in south central South Dakota and western Nebraska.

Local life. One or more species of the carnivore-like creodont Hyaenodon probably occurred here in the Oligocene. Oreodonts also were diverse, then, and likely were represented here. There were widespread, hippolike rhinoceroses called amynodonts in North America and Eurasia. Horses in the genus Mesohippus also were likely here.

One More For the List

by Carl Strang

One product of my continuing natural history survey at Mayslake Forest Preserve is a set of species lists. As of the start of this year, I had observed 14 species of mammals or signs of their presence on the preserve. In addition, there is evidence of past activity by beavers, in the form of old beaver-cut trees.

No beavers are presently on the preserve, however. When I moved my office to Mayslake in late 2008, it was past the time when woodchucks would have entered hibernation. I fully expected to find them on the preserve. The habitat looked right. However, I have yet to see one or any tracks there. The closest woodchuck I have seen to Mayslake is one that is active along the edge of 31st Street a quarter mile or so to the west.

On one of my recent lunchtime walks I found an old skull fragment in the prairie just north of the stream corridor marsh.

The skull’s size, the arrangement of the molar tooth root holes, and the flattened or slightly depressed top of the head all point to a single identification: woodchuck. So, they have been at Mayslake, and could well appear again, but for now I have to include the species on the preserve list as a past presence only.

I close with a koan: Groundhog or ground hog? Woodchuck or would Chuck?

A Visit to JPPSP/Tri-County

by Carl Strang


Its official name is James Pate Philip State Park, but I prefer the shorter, more descriptive original name, Tri-County State Park. The park contains the point where Cook, DuPage and Kane Counties meet, though most of it is in DuPage. The park is remote enough that it has the capacity for unusual events. Arguably the most unusual this year so far is a growing osprey nest.




When I stopped by the park for a brief visit on Saturday, the ospreys were present but not at the nest.




Later they both flew to their nest, their size revealing how huge is the platform provided by the utility tower.




With that elevation and exposure, I wonder about the hazards of lightning and the winds that accompany thunderstorms. This almost certainly is the same pair that nested just northwest of the park last year, as I mentioned in an earlier post on the species.


There were no great blue heron nests in the dead trees that still stand in the marsh on the island that bears one of the beaver lodges. Earlier  I mentioned the tiny nesting colony that was sited there for a few years. Here is one of the nests in 2005.




Elsewhere, I found the beavers’ dam just above the trail’s bridge in tidy order.




This actually is one of a series of dams along this stream. There has been an ongoing tug-of-war between the beavers’ instinctive drive to maintain their pools, on the one hand, and peoples’ need to prevent the resulting overflow from washing out the trail. On Saturday there was at least a temporary equilibrium, with both dam and trail intact.


A final note from that visit was a killdeer nest, placed where the nervous parent is bound to be flushed many times, at least on weekends, by passersby.




The incubating bird was quick to jump up and run away, but at least in my presence did not perform the famous broken wing act.




I did not bother the nest, and left after taking a few quick photos. The park does not get huge volumes of visitors, so I’m hopeful the eggs have a chance.

Alphabet of Tracking 3: Other Toe Counts

by Carl Strang


I’ll conclude the alphabet portion of this abbreviated tracking primer with species which typically show two toes, and those which register four toes on the front feet and five on the hind feet.


Two-toed feet mean white-tailed deer in the wild fauna of today’s northeast Illinois. In the photo, a hind footprint partly overlaps a front footprint.


White-tailed Deer

White-tailed Deer



The four-five combination indicates members of the rodent family. Three examples follow. Our largest rodent is the beaver. Here is its four-toed front footprint.


Beaver front footprint

Beaver front footprint



In muskrat tracks the hind footprint is much larger than the front footprint. Can you find all five toes belonging to the hind print to the left in the photo, and all four toes on the front foot to the right?


Muskrat tracks

Muskrat tracks



This set of squirrel tracks has four footprints. The outer prints are the hind feet, the inner ones are front feet. Some study may be required to find all the toes, but they all are showing.


Squirrel tracks

Squirrel tracks



The next lesson when I return to this topic will introduce typical footprint arrangements, or gaits, of these animals.

Biology Along the Way

by Carl Strang


Though my trip to Canada had as its primary goal an exploration of the route of the Lake Michigan lobe of the Wisconsin glacier, an old wildlifer like me was not going to ignore the vegetative communities and wildlife along the way. I was especially interested in what I would find in the highway loop through Timmins and Hearst, Ontario, as I had never been in that area before. It’s far enough north that I passed a sign marking the watershed for rivers flowing north to the Arctic Ocean and those flowing south.




Potholes Provincial Park along Highway 101 had a little trail going to some beautiful places. The trees along the edge of this photo are black spruces, a tree of special interest because we found a couple cones of this species in the mastodon dig this summer (more on that in future posts). Black spruce was the dominant tree in many places this far north, though it no longer occurs closer to Illinois than central Wisconsin.




Kettle Lakes Provincial Park has a great trail system. Here are some photos showing a segment through paper birch,




another past savanna-spaced pines,




a closeup of lichens and a club moss.




There were edible blueberries,




beautiful bunchberries,




asters still flowering in September




but the changing colors of plants such as these honeysuckles revealing the season.




Signs of animal life included a beaver lodge in every little lake,




dew-highlighted spider webs,




and a spruce grouse.




Tomorrow I’ll conclude with wildlife at Nagagamisis Provincial Park.

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