Eastern Cottontail Dossier

by Carl Strang

My species dossiers focus on vertebrate animals, and as there are many more birds than other terrestrial vertebrates, most of the dossiers I have shared had avian subjects. Today’s focus is a mammal.

Cottontail, Eastern

These live in weedy and brushy habitat. Occasionally enter forests, especially in fall and winter. Maintain a network of trails and runs. Have aboveground forms or beds used for much of the year, but take cover in sheltered spots (in firewood pile at Warrenville, IL, for instance, during daytime in a neighborhood with little cover) and in burrows (woodchuck burrows at Culver’s fish ponds, skunk burrow at Willowbrook), and culverts. Predators may influence this: in winter of 1998-99, cottontails seldom appeared in the open, but coyotes were omnipresent and often dug at ends of drainage culverts under the nature trail, where rabbit tracks led.

Cottontail nest, opened slightly to show hairless infant.

Young born blind and hairless. Nest in short grass areas (e.g., lawns, examples seen at Boiling Springs, PA, and in IL), in shallow depression lined and covered with a mix of fur and grass. Nest well hidden. Young become independent when about 4 inches long, when ears stand up and fur becomes shaggy. Mother simply abandons nest (normally she visits it only at night), young find their way out. Observed a youngster at Lombard, IL, learning to recognize food. Sniffed every plant, occasionally nibbling one, occasionally chewing one down to ground. Can be tame and easily caught first day or two out of nest.

Summer food green plants, for instance dandelions (watched one at Boiling Springs, PA, as it ate fruiting stalks, biting them off near ground then nibbling them into mouth endwise, seed poofing out as it reached the end). Browses in winter. In DuPage County, rose family preferred (or at least eaten first, then when other foods depleted, larger rose and Rubus stems cut to bring twig ends within reach), others eaten include twigs of maple, elm, bittersweet Solanum dulcamara, poison ivy (the last toward winter’s end). Patches of red to orange urine at this time. Bark of cherry, elm, sumac, taken in leaner winters.

Often the toenail marks are the only clear indicators of a cottontail track. The furry feet do not make a clear impression in hard soil.

Droppings distinctive, round. Tracks occasionally show the 4 nailed toes in good conditions. Hard substrates sometimes reveal 4 toenail marks in wedge shaped pattern. In snow, typically nothing more than round depressions for front feet, elongate ones for hind feet. Rarely anything but a gallop gait with one front foot in front of the other.

16AP86. Rabbits eating gray dogwood bark in Willowbrook Back 40, both of standing shrubs and of stems I cut earlier this week.

9JL86. Watched a half-grown cottontail through the window at Willowbrook as it grazed. Seemed to select younger grass blades (pointed rather than mower-cut; lighter in color).

9FE87. Inside Willowbrook main building, cottontail escaped from intensive care room during night. Droppings and smears of dust suggest that it got into the clinic, somehow got up onto 3 foot high counter top, then another 4 feet up to cabinet top. [I asked Tom Brown about this; he has seen even higher vertical leaps onto ledges by cottontails].

This is the cottontail that escaped in the Willowbrook Wildlife Center hospital and hid by jumping from the floor to the countertop, then from the countertop to the top of the wall cabinet.

12FE87. Cottontail recently gnawed on crabapple beside trail.

15MR87. Meacham Grove. Rabbit moving fast, but turning: the space between the front feet and hind feet decreased as it approached the turning point, revealing a slight deceleration; the front feet pointed in the direction it had been going, then the hind feet pointed in the new direction. This rabbit placed its front feet side by side. The distance between the front and hind tracks was not related to the distance of the leap: large and small for long and short hops. I tracked this rabbit to its hiding place, partly under a log in open woods. I had passed within 8 feet of him twice, then stood 3 feet away for at least 2 minutes puzzling over tracks that seemed to go into there but not out, when he burst from hiding and ran away. The rabbit had climbed up on sticks and logs a few times (crossways to his route).

A typical cottontail footprint pattern with the more elongate hind footprints side by side, rounder front footprints one before the other. In each step the hind feet carry past the front feet.

MY87, NJ Pine Barrens. Cottontail browsing blueberries, oaks.

AU87, NJ Pine Barrens. Cottontails smaller here than elsewhere.

12AU87. Assateague Island, morning. Young cottontail eating clovers (several patches well nibbled, English plantain flower stalks, a wiry upright narrow-leafed composite, and another plant that resembled common ragweed. Avoided the abundant Senecio. Had several ticks in its ears, and appeared to have a partial cataract in the right eye.

18DE87. 4 days after an abrupt 1-foot snowfall, little but rabbit and squirrel tracks in Willowbrook Back 40. Former’s mainly at edge of field and woods.

23JA88. McDowell Forest Preserve. Rabbits and foxes highly active last night (an inch of snow fell just after sunset). One rabbit, at least, was in underground burrow during snow. Unusual amount of side-by-side front foot placement by rabbits: slippery or uncertain new surface? One rabbit fed on grasses, edge of a tall grass field.

On slippery or unfamiliar surfaces (e.g., the first snow of the season), cottontails often lock their front feet together side by side. I assume this gives them more stability. You can see in the dossier text when I discovered this.

27JA88. Willowbrook. A rabbit had moved along left edge of path, paused and looked back down path over right shoulder. Both front feet to right of their usual position and pivoted, right foot 45 degrees. This is enough to allow the rabbit to look behind it (eyes on sides of head).

28JA88. Willowbrook. A rabbit did heavy browsing on a rose bush last night.

3FE88. Willowbrook. In the 2 nights since the last snow, not real cold, lots of activity. Rabbits, squirrels, mice, fox, raccoons, cats. Icy beneath. Again, lots of rabbit track sets with side by side front footprints.

LateFE88. Tracker Farm, NJ. Rabbit browsed rose since 1 JA.

6JE88. Baby rabbit tasting rocks, licking them, in Willowbrook streambed. Ate silver maple seed, elm seedling.

13DE88. Rabbits commonly placing front feet side by side on longer steps after about an inch of snow fell early last night atop the half inch that was there from 3 days previous.

1MR89. Rabbit’s front feet indicate the direction from which it came more reliably than the hind feet point to where it’s going, at least when it is traveling slowly. Look to pressure releases as well. In today’s crusty snow, the rabbit leans in the direction it’s going, so that in forward hops the toes are deepest. In an abrupt left turn the left edges of both hind prints were deepest.

12MR89. Hartz Lake. Dense poison ivy area between cemetery and prairie heavily browsed recently, mainly by rabbits.

25AP89. A rabbit nest, now empty with lining scattered. In the low, flattened blackberry tangle beside the nature trail at Willowbrook. Scattered taller brush on all sides.

These baby cottontails are weaned or nearly so. The mother simply stops coming to the nest and the young, driven by instinct and hunger, leave the nest and start learning which plants are good to eat.

3MY89. Willowbrook. Another rabbit nest yesterday on the side of the hill constructed of fill from marsh excavation. Like the nest last summer on the steep hillside at Clarks’, this hole was deep.

4MY89. Willowbrook. Yet another rabbit nest, this one in fairly thick brush 5 feet beyond the cleared edge of the main trail.

9MY89. I mistook moss for a cottontail. Sometimes the agouti pattern resembles mossy mottling.

22JE89. Rabbits eating common ragweed at Willowbrook.

31JL89. Willowbrook. Rabbits bending down Queen Anne’s lace and common ragweed and eating tops, along Nature Trail.

18AU89. Cottontails reaching common ragweed tips 4 feet off ground. Apparently, from bruise patterns and broken stems, they are pulling the plants down.

24NO89. Hartz Lake. Rabbit stopped, sat, turned. Entire left edges of both hind feet show pressure releases.

13DE89. Hartz Lake. No consistent ratio of track-set length to space between sets. A ratio of 3-4 common in shallow snow (front feet side by side, mostly). Degree of forward lean or toe-dig of back feet a better indicator of step length.

16FE90. Rabbit sitting on top of snow in Warrenville, IL, back yard, out of reach of anything edible, chewing cud. Bent down a couple of times to get feces for re-ingesting, taking them from anus with mouth.

16MY90. Rabbits have been eating fleabane tops.

12SE90. Watched young (nearly full grown) cottontail feeding, at close range. Eyes cranked forward, showing the tiniest bit of white at the back, as the rabbit examined and ate plants. Ate fruits and leaf blades of roadside rush and crabgrass. Seemed, however, to be using smell more than vision in checking out potential foods. I could get away with some movement when the eyes moved forward.

5JL96. Cottontails chasing each other 11a.m., picnic shelter area at Willowbrook. The chases were brief, sometimes extending into brush, but generally about 20 yards at most and often half that. They then would stop as the pursuer peeled off, but then often the chased animal approached, clearly soliciting another chase. Sometimes the chases were moderate in speed only, sometimes there were brief very fast spurts in the middle.

16MY98. Cottontail at Willowbrook eating blue violet leaves (nearby: flowering motherwort mint, garlic mustard).

28JA99. Cottontails this winter not visible during the day. Tracks indicate they are hiding in metal drainage culverts. Coyotes occasionally vainly try to dig them out or, perhaps are trying to spook them out.

10MY99. Cedar Springs, Michigan. Cottontails mating. Smaller adult chased larger, caught up, mounted and very quick small thrusts for a couple of seconds, then larger ran away and pursuit resumed. In woods clearing.

Here a mother rabbit at Mayslake covers her nest shortly after giving birth.

29AP09. Mayslake. As I drove in, I saw a rabbit digging in the lawn of the long parking lot island beside the drive. Three other rabbits were nearby, and one eventually chased her away from where she was digging and I saw him mate with her once. I thought she was still digging soil, but perhaps she was digging out grasses to cover the nest with (supported by her relative skinniness in photos). I returned at mid-day, found 5-6 babies in the nest there. Soil still beside the nest, but flattened. Babies born last night or this morning, it appears. (These rabbits eventually weaned and left the successful nest).

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Plants in Winter: Cinnamon Willow Herb

by Carl Strang

Last winter I started a series of posts on winter botany. I had been thinking about resuming it, and then earlier this week the issue was forced. I used a route I may never have taken before to pass between Mayslake Forest Preserve’s south stream corridor prairie and the mansion grounds, and found myself walking through a scattered array of cinnamon willow herb plants. They were delicate and beautiful.

The willow herbs are close relatives of the showy fireweeds common elsewhere on the continent.

Unfortunately, the photos of entire plants flatten them out too much, and don’t convey the impression I would like to share.

The opened slender seed pods at the tips give the plants a feathery appearance.

A close-up of one of the tips comes closest to showing the distinctive spray of the open pods.

Close up, you can see a few seeds still clinging to one of the pods.

Here is what the plant looks like when flowering.

The flowers of this late-season bloomer are small.

The cinnamon willow herb is the most common member of its genus in northeast Illinois. Usually it grows in open moist areas. Beyond that I am afraid my knowledge of it is limited.

Literature Review: Population Edges

by Carl Strang

Today I want to share my notes from a couple papers published last year in the open on-line scientific journal PLoS ONE (Public Library of Science). These studies looked at the geography of populations. The first considered the ecological factors that determine the edges of a species’ range [Rhainds M, Fagan WF (2010) Broad-Scale Latitudinal Variation in Female Reproductive Success Contributes to the Maintenance of a Geographic Range Boundary in Bagworms (Lepidoptera: Psychidae). PLoS ONE 5(11): e14166. doi:10.1371/journal.pone.0014166].

Here is a bagworm case, formerly the home of a female but now containing her eggs, in a crabapple tree at Mayslake Forest Preserve.

They looked at bagworm populations from Tennessee to Michigan to determine what limits their range. Caterpillars of this moth live in protective cases that they build around themselves. Wingless females mate in fall with flighted males, lay eggs in their bags, then drop to the ground and die. The eggs hatch in the spring. Female mating success dropped from near 100% to near 0% as the edge of the range was reached (apparently as the population thins out, males have a hard time finding females). Other factors were declines in fecundity, egg and pupal survivorship (all perhaps attributable to stresses resulting from the northern climate). The population density thins and local extinctions become more frequent toward the edge of the range.

Here’s another bagworm egg case, this one on a willow at Willowbrook Forest Preserve.

This study was of personal interest because I have been looking at several instances of range extensions in singing insects.

The other paper reported a study of mammal communities in forest fragments in Brazil [Pardini R, Bueno AdA, Gardner TA, Prado PI, Metzger JP (2010) Beyond the Fragmentation Threshold Hypothesis: Regime Shifts in Biodiversity Across Fragmented Landscapes. PLoS ONE 5(10): e13666. doi: 10.1371/journal.pone.0013666].

This scene is from Panama, not Brazil, but may be similar to the kind of landscape Pardini and company were studying.

Community ecologists are concerned about what happens to species diversity as large blocks of habitat become broken into smaller pieces by human activity. These scientists found a landscape-wide threshold in total forest coverage below which species went extinct throughout the system. In other words, local extinction in island-like patches of habitat no longer could be replenished through immigration from other patches because there weren’t enough of these to serve as sources. I found similar patterns in my study of periodical cicadas in DuPage County in 2007.

Skunk Den Search

by Carl Strang

Last Wednesday, when tracking the skunk at Mayslake Forest Preserve, I ran out of time before I found its den. On Friday I decided to see if I could finish the job. I first went to a known den in the north part of the preserve, not far from where some of the trail had led me. It was a very cold day, and the little stream was completely frozen over. Some beautiful ice crystals had frozen on the surface.

Ice on ice. This sight alone justified coming out in the cold.

There were many beautiful little scenes within the bigger one.

The known den had not been entered or exited since the snowfall. It is possible that this one contains a skunk that stayed home Monday night, or that the skunk had moved out, or it may be in there but dead. Mammalogist Stan Gehrt has found that in northeast Illinois, winter mortality takes out half the skunks typically (the loss is less in mild winters).

A coyote had sniffed at the den, but that was it.

I went back to where I had left the skunk’s trail on Wedneday, heading east past the north end of the parking lot marsh. It turned and went along the top of the ridge that runs between the marsh and the stream to the east.

The ridge clearly is a human construct, formed when the marsh was excavated.

Midway along the crest of the ridge was a hole. It appeared that the skunk had exited and entered it Monday night, but the definitive tracks were obscured by some enormous ice crystals that were forming around the edge of the hole.

I hope you can see the very large crystals growing across the hole.

It was only later, as I was returning to my office, that I realized how odd those crystals were. It occurred to me that they might be forming out of moisture from the skunk’s breath. This was a new possibility, a way of identifying an occupied den under certain conditions such as very cold weather. Next month, during the skunk mating season, I’ll get more opportunities to see if this hole is a skunk den.

Prehistoric Life 10

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.

Permian Period (286-251 million years ago)

The Permian Period was named for the Perm District of Russia (1841), added because the fossils found there, though distinctive, were recognizably between those of the Carboniferous and Triassic periods. It began with a glacial period, and the fusion of the continents into the supercontinent of Pangaea. Its ending (and that of the Paleozoic Era) was a massive extinction of as many as 95% of species, now correlated with the largest known volcanic eruption in the history of the Earth, in Siberia.

Life on Earth. Trilobites became rare during the Permian, and the last of them vanished when it closed. This was the last time in which brachiopods were important, continuing to diversify during the Permian, but having many extinctions, and becoming relatively unimportant after the Permian. Snails and clams were relatively unimportant, but ammonoids (octopus relatives living in coiled shells) became widespread and diverse.

The drier climate of the Permian led to the rapid decline of the giant club moss and horsetail forests. Conifers, cycads, ginkgoes and seed ferns, which better protected their seeds from drying out, became dominant.

Ostracods and insects became more abundant. The proto-dragonflies still were around, e.g. in Kansas, and the modern Odonata, which may have evolved from them, appeared early in the Permian, as did the true bugs, scorpion flies, caddis flies and Neuroptera.

Here is part of an exhibit on Permian animals at the Field Museum of Natural History. The predator Dimetrodon is in the upper left corner.

There were two important groups of synapsids in the Permian. The pelycosaurs (e.g., carnivorous Dimetrodon and herbivorous Edaphosaurus, both known from Texas) often had long, sometimes branched spines down their backs, usually depicted as supporting a sail-like structure that they possibly used in thermoregulation. Pelycosaurs became extinct in the last half of the Permian. The other synapsids were the therapsids, often informally called mammal-like reptiles, the mammalian ancestors. The therapsids are thought by most to have descended out of the pelycosaurs; they appeared at about the time the pelycosaurs vanished. Cynodonts are the therapsid group ancestral to mammals, emerging in the late Permian.

There were reptiles other than synapsids in the Permian. This pareiasaur is an example of another group, the anapsids (again, part of the Field Museum exhibit).

Amphibians declined, though a number of large ones are known from Texas, including Eryops. There was also the bizarre, wide-skulled Diplocaulus of North America. The dry climate resulting from the formation of Pangaea boosted terrestrial vertebrates with shelled eggs; amphibians were at a disadvantage.

The Permian ended with massive extinctions, apparently the most severe the world has seen, with possibly only 5-10% of marine species and 10-35% of terrestrial vertebrates surviving. The cause is unknown, but various climatic and geological upheavals would have accompanied the collision and fusion of continents that was happening then. Two recent studies suggest that a sudden major release of methane gas may have been the direct cause of the extinctions (Science 301:1168). Other studies closely tie the extinctions to the time of the most massive volcanic eruption in Earth’s history, in Siberia (Science 305:1705, 320:434-435). Toxic hydrogen sulfide, another gas that could have been released in large amounts by volcanic eruptions, also spiked in the atmosphere at that time (Science 307: 706). The Permian was a time of stress also because atmospheric oxygen levels appear to have dropped from 30% in the early Permian to only 12% in the late Permian. This would have limited terrestrial animals to isolated pockets of habitat at low altitudes. In addition to measures of oxygen, the fact that one of the few surviving therapsids was a tunneling species (Lystrosaurus), presumably pre-adapted to low oxygen, provides support for low oxygen as a contributing factor (Science 308:398; see also Science 309: 2202). This is underlined by the fact that at least 90% of surviving terrestrial vertebrates in South Africa and Antarctica were Lystrosaurus, which also is known from South America, China, and Russia.

Local landscape. The Permian is the only Paleozoic period with no remaining deposits anywhere in Illinois (the closest areas with Permian bedrock are in the southeastern corner of Nebraska and in southeastern Ohio). Our area was land then, the seas well east and west of us. There was geological activity, though, as a magma body moved into Mississippian limestones during the Permian, creating Illinois’ fluorspar deposits and giving us our state mineral. This event probably was the result of the collision between the northern supercontinent of Laurasia with southern Gondwana to form Pangaea. Much as today’s Himalayas are building from India’s push into south Asia, a Pangaean mountain range (persisting in part as the Appalachians) extended from what is now the Gulf of Mexico to New England and Canada’s Maritime Provinces and beyond. This mountain range had an east-west orientation and was just north of the equator, with the result that our part of North America was a desert. North America was united with South America (the northern bulge of which fitted the Gulf coast) and Africa (Africa’s west coast fitted against South America and North America together).

The ice age described for the Pennsylvanian Period continued into the early Permian, but was limited to what are now the southern continents. Later in the period, atmospheric carbon dioxide rose to the point where its greenhouse function prevented glacial periods from occurring, and this inhibition continued until the Pleistocene. The warming selected for increasingly drought-tolerant plant communities as the Permian progressed, for example favoring conifers at the expense of tree ferns and seed ferns (moisture-loving plants persisted in limited low, moist refuges).

Local life. The best guess may be that we had local savannas to desert woodlands of the plant groups mentioned above, with a variety of insects, and some therapsids and pelycosaurs. Local streams would have had fishes and amphibians. But to the extent that this area was elevated, and the oxygen depletion mentioned above was a factor, there may have been a biological depletion of our central part of the supercontinent.

Blob Tracking

by Carl Strang

The title for this entry is not a technical term. It simply refers to the interpretation of tracks that are blobs rather than well-defined footprints. The mix of rain and snow we experienced on Monday provided a good opportunity for this practice. Here’s an example from the south savanna at Mayslake Forest Preserve.

What do you make of these blobby footprints?

Here an opossum was walking, left to right in the photo. As usual, the oddly shaped hind foot with its enormous big toe is turned sideways. The more uniform toes of the front foot are widely spread. The left-hand pair of blobs were made by the right feet, the middle pair by the left feet, the right-hand pair by the right feet again. You can see clearer reference examples in my tracking primer here.

I was interested to see that a raccoon had circumnavigated May‘s Lake Monday night, with various side trips into different woodlands, up and down a few trees, etc.

Do you recognize these as raccoon tracks?

The blobs in this case are recognizable as raccoon tracks because of the side-by-side pairs of footprints, indicative of the raccoon’s distinctive pace gait. Their size and spacing are consistent with the raccoon’s body size. Raccoon activity was especially concentrated in the west end of the south savanna, not far from the former friary, and the footprints had merged into the distinctive trails formed by the big flat feet of raccoons when they travel a route frequently.

Raccoon trails are easy to see in winter.

I suspected the raccoon’s den must be in this area, and sure enough, the trail led to a concrete culvert that empties into May’s Lake.

The trail comes to the culvert from the left and enters along the left edge.

In contrast to the blobs that the raccoon made during most of its excursion, it left very clear tracks as it entered the culvert. The animal still was inside, as there were no exiting tracks.

If you look closely you may be able to see a few clear footprints on the trail.

The possibility is open that more than one raccoon is involved, and that the one in the culvert was different from the one that went around the lake. This may seem a strange choice for a den, but it’s secure, and probably dry enough this time of year. I wonder if this might be the raccoon that used to live in the friary. That animal, evicted by the demolition, had grown accustomed to denning in a human structure. The concrete culvert might seem a more comfortable new home than a hollow tree.

Today’s final example had me fooled at first. This animal was doing a lot of its travel with the bound gait, and my interest in the mink had me thinking I had found a mink’s trail.

These sets of four tracks are in a pattern typical of the bound gait.

Again, you can find a description and clear photo of a mink’s bound gait pattern at the post on gaits. Eventually I had to abandon my initial idea. These footprints were too small and narrow, the sets of tracks were too close together for such shallow snow, and this animal was spending a lot of time downshifted into a diagonal walk.

The animal in question was slowing to a diagonal walk gait whenever it entered taller vegetation.

It doesn’t happen that often in mid-January, but a skunk had come out and covered a lot of ground Monday night. The temperature was in the 20’s that night, the warmest of the month, so it was not so far out of the realm of possibility. Still, it merited an entry in my skunk dossier.

Experiment on Self: Progress Report

by Carl Strang

Last fall I outlined the debate in distance running circles about the growing minority of runners who are running barefoot or using minimal shoes that approach the barefoot condition. At that point I had bought but not yet tried a pair of the most extreme shoes on the market for the barefoot style of running.

The Vibram Fivefingers running shoe is the most extreme of those that have been designed for the barefoot running technique.

I am at the 4-and-a-half-month point in this physiological experiment. So far things are progressing well, and I have reached my initial mileage volume goal of running 4 miles 3 days in a row, then taking a cross-training day on the bike trainer. Most of those runs now are in the Fivefingers shoes, and I continue to become stronger in them. Even though I had prepared for a couple of months by using the barefoot technique in conventional running shoes, I went slowly with the Fivefingers. The absence of all heel lift makes a surprising difference in the calf muscle’s involvement, and it is taking a while to gradually build my calf strength. I went ahead and bought a less radical pair of shoes which nevertheless are designed for the barefoot technique, and for a while ran in them on days when my feet or calves were a little more sore than usual.

Newton running shoes also are intended for the barefoot technique. The extended sole elements under the ball of the foot are part of the design.

At this point I am beginning to incorporate occasional longer runs (a recent 6-mile run was my farthest in 18 years), as well as some faster pace and interval work, and I am using the Newtons for those workouts.  My pace, though slow, continues to improve. Where at first I was less than comfortable at 9 minutes per mile, now I can cruise at 8:15, and can do an occasional mile in less than 8 minutes without undue strain. I repeat the caution I read about often when first researching the barefoot method. Go slowly, don’t be impatient to build the speed and mileage. So far, so good.

First and Last Song Dates

by Carl Strang

For five years, now, I have noted the first and last dates on which I hear each singing insect species. This allows me to look at the phenology of the singing insects as a whole. Was 2010 early or late, compared to the others? Here is what I found: 11 species with the earliest song dates in 5 years, 12 with second-earliest, 2 with third-earliest, 2 with fourth-earliest, and 2 with fifth-earliest. This distribution seems to indicate an early season for starting dates, and indeed it departs from the expected even distribution when I apply a chi-squared test (χ2 = 18.76, p < 0.01).

In northeast Illinois, the first singing insect to begin its display is the green-striped grasshopper. Its earliest crepitating song flights can be heard in April or May.

The distribution of last observed song dates was more even among years, though possibly suggesting a shift forward consistent with their early start: 3 species with latest song dates, 4 with second-latest, 5 with third-latest, 8 with fourth-latest, and 7 with fifth-latest. The difference from an even distribution was not statistically significant, however (χ2 = 3.11, p > 0.01).

The three common species of ground crickets consistently close out the season, their songs continuing into November.

Looking at the snow outside, I know I have a 3-4-month wait until the next singing insect season begins.

Snowstorm and After

by Carl Strang

I go for a walk in Mayslake Forest Preserve during my lunch break almost every day I am there. Sometimes in winter there will be a snow storm, and the different mood of the place is worth going out and experiencing.

Here’s a view of May’s Lake during a recent storm, with a cautionary sign for polar bear wannabes.

The day after a snowstorm my eyes are on the ground a lot, as there is a good fresh record of animal activity. I usually can count on the coyotes having covered much of the preserve the night before.

Here a coyote passed along the north edge of the mansion grounds. The partially filled tracks indicate that the animal was active the previous night while snow still was falling.

I am happy to report that the mink has been a regular visitor. Here it was following the little stream toward its origin as May’s Lake’s outlet, and encountered an ice shelf it had to cross.

The mink probably would have preferred to stay in the water.

Here the mink accelerates to its traveling bound gait.

Not slowing down a bit, the mink seems anxious to get back in the slightly warmer (and more secure) water.

The mink tracks were sharper than the coyote’s, having been made after the snow stopped falling. So far this winter all the mink signs I have seen have been consistent with a single, wide ranging individual.

Prehistoric Life 9

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.

Pennsylvanian Period (320-286 million years ago)

The Pennsylvanian Period is named for the state of Pennsylvania (1891). This North American subdivision of the European Carboniferous Period is distinguished by many cyclic repeated advances and retreats of the sea, as indicated by alternating rock layers.

Life on Earth. This was the time of the coal forests, when the growing land area provided the home for forests of lycopsids (club mosses, the most abundant trees), sphenopsids (the group containing today’s scouring rush, horsetails and other members of genus Equisetum), ferns (including tree ferns), and seed ferns. There were early conifers as well. These were vascular but not flowering plants. Most coal was produced during this period because fungi, critical to decomposition, had not yet developed that ability to a significant extent. Dead plant tissue piled up without breaking down, ultimately was buried and fossilized into coal. As a result, oxygen built in the atmosphere to an all time high of 30% (Science 316:557).

You can see a life-sized reconstruction of a Pennsylvanian forest at the Field Museum in Chicago. Here are some model sphenopsids.

The earliest Amniota (the terrestrial egg-bearing group ultimately including reptiles, birds and mammals) appeared and diverged in the Pennsylvanian, producing the cotylosaurs (and other anapsid reptiles, a group represented by turtles and tortoises today; fossil cotylosaurs have been found as close to Illinois as Nova Scotia), synapsids (also known from N.S. and the group from which mammals ultimately evolved; the basal synapsids are referred to as pelycosaurs), and the diapsids, a reptile group that evolved into lizards, snakes, dinosaurs, birds and crocodiles.

Winged insects (including the first mayflies and enormous primitive dragonflies) first appeared in the Pennsylvanian, as did cockroaches, grasshoppers and crickets. The earliest beetle was reported from Illinois fossil material in 2009 (J. Paleont. 83:931). Some invertebrates, such as the dragonflies and certain millipedes, reached giant sizes (thanks at least in part to the elevated oxygen levels).

Local landscape. In Illinois, the sea continued its advance and retreat cycling, so that our area alternated between marine and land, often low and swampy. Our area remained just south of the equator, and the climate was warm and humid.  It is thought that alternating periods of glaciers forming and thawing on the southern Gondwana supercontinent (at that time drifting over the South Pole) caused the rises and falls of sea level that produced the local advances and retreats of the sea. Over geologic time, glacial episodes typically are associated with a continental mass at one of the poles (Antarctica in recent times).

Tree ferns still exist today. This one in Tasmania had a thick stem more than 10 feet tall.

The North American continent was beginning to collide with Europe and Africa as the sea that had begun to appear between them closed, forming the northern supercontinent of Laurasia. This event is what lifted our part of the world above the sea for good.

The nearest Pennsylvanian bedrock to Chicago is the Mazon Creek area (much of Illinois’ bedrock is Pennsylvanian), except for some bits in the Des Plaines Disturbance.

Local life. Coal forests dominated Illinois during the Pennsylvanian. Not only was coal left (itself fossil plant material), but remains of a variety of plant and animal fossils can be found just a little south of us in the world-famous Mazon Creek deposits of Middle Pennsylvanian age, just a little southwest of Joliet. Seed-fern leaves such as Medullosa, Neuropteris inflata, N. scheuchzeri, N. ovata and N. rarinerus are especially abundant (note: names of these plants are confusing, because different names are given to different parts such as leaves, stems and reproductive parts). There also were the giant sphenopsid Calamites, the smaller weedy horsetail Sphenophyllum, the tree fern Psaronius, small ferns (Pecopteris, Sphenopteris, Alloiopteris), the conifer relative Cordaites, giant club moss relatives Cyperites, Lepidodendron, Lepidophloios, and Sigillaria (up to 6 feet in diameter!), and other, smaller club mosses (Lycopodites, Bothrodendron).

Here are some giant club mosses in the Field Museum exhibit.

Most bizarre among the diverse aquatic animals was the Tully monster (Tullimonstrum gregarium), first found by amateur fossil collector Francis Tully, Illinois’ state fossil, and only known from this area. There were horseshoe crabs (Palaeolimulus, Euproops), freshwater fish (Rhabdoderma oxiguum, Conchopoma edesi, Elonichthyes peltigerus, Platysomus circularis), and mollusks, as well as a lamprey-like fish, Actinopterygian fishes (Elonichthys pettigerus, Platysomus circularis), polychaete worms (Astreptoscolex anasillosus, Escorites zelus, and others), shrimps (Belotelson sp., Kallidecthes richardsoni, Acanthotelson stimsoni, and others), a sea cucumber (Achistrum sp.), a nematode (Nemavermes mackeei), a chiton (Glaphurochiton concinnus), ribbon or priapulid worms (Archisymplectes rhothon, Priapulites konecniorum), the arrow worm Paucijaculum samamithion, the spoonworm (phylum Echiura) Coprinoscolex ellogimus, jellyfish (Essexella asherae, Octomedusa pieckorum, Anthracomedusa turnbullii), cephalopods, brachiopods (Lingula sp.), the scallop Aviculopectin mazonensis, as well as several “mystery animals” of unknown affinities. 

The Field Museum model forest includes a millipede you could put a saddle on!

Land animals included centipedes, millipedes (the giant millipede Arthropleura cristata was a flat species, 16” wide and more than 6 feet long), scorpions, cockroaches (Platymylacris paucineruis) and their relatives (Gerarus danielsi, G. vetus), and spider-like arachnids. There were amphibians (Amphibamus grandiceps, A. yelli).

The upland trees, less well known, were different from those in the swamps, and included the genera Megalopteris and Lesleya. An upland animal was the scorpion Labriscorpio alliedensis.

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