Whitetail Deer Dossier

by Carl Strang

It’s time to start sharing some of my larger files of notes from personal observations of our vertebrate wildlife. This week’s feature is our local hoofed critter. The preliminary notes, written in the mid-80’s, are more extensive than usual. The dated notes that follow provide many illustrations of the value of tracking in behavior studies.

Deer, Whitetail

Buck in a bed

Buck in a bed

Deer can be seen in a variety of habitats. Their home range always includes some woodland, brush and meadow or marsh areas. They travel on well used trails, occasionally wandering off them to feed. Commonly they enter meadows to feed at dusk. In winter, they feed on browse. In northern Illinois they hit Rosaceae (blackberries, roses, etc.) early in winter, then eat a variety of woody plants, then by mid-February are eating poison ivy almost exclusively. Cottontails follow the same sequence of foods, but deer-browsed twigs usually are bitten off higher and have a torn edge from the deer’s lack of upper incisors. Through January (though mainly in October and November), bucks attack certain shrubs and saplings along trails, breaking twigs and usually also eating a couple (antler rubs). At Herrick Lake Forest Preserve I noticed that pioneer bur oaks in fields were especially exposed to this abuse.

Shrubs missing bark after being rubbed by a buck’s antlers

Shrubs missing bark after being rubbed by a buck’s antlers

Does in spring have fawns which at first remain quietly curled up on ground, freezing when approached. If they do wander, they will call for mother with a sheep-like bleating sound. As their size and strength improve they begin to travel with mother, although on occasion they will drop into a frozen curled position when a threat is detected. Spots can remain into late summer.

Deer flushed close have tail-lifting display, spreading the white hairs underneath (on small fawns the display is disproportionately large). At a distance, when at least partly in cover, they give a high-pitched, whistling snort, often accompanied by a stomping of the feet.

Bony antlers grow slowly through summer, covered with velvety skin. In late fall they dry, the skin comes off. By spring the antlers have been shed.

Tracks usually are 2-toed hoof marks. Leaping deer or those in deep soft substrates also will make 2 smaller dewclaw prints. In deep snow, the tips of the nails often make drag marks. I have seen deer leap over 6-foot fences, and tracks have shown horizontal jumps of more than 12 feet.

In May, deer on Reineman Sanctuary (PA) fed on fiddleheads of hay-scented ferns, but didn’t touch them after they unfolded. Among summer foods were leaves and twigs of greenbrier.

Deer tracks typically show two toes. Here, a deer was walking but accelerating.

Deer tracks typically show two toes. Here, a deer was walking but accelerating.

27DE86, Memorial Forest near Culver: deer recently browsed sassafras.

10JA87. Herrick Lake Forest Preserve. After last night’s heavy snow, tracks (made this morning, early) only abundant at a large patch of brush in SE corner of preserve, along N edge. All made early this morning except one flushed by a person who was tracking it.

11JA87. Waterfall Glen Forest Preserve. Deer were bedding in snow in same general area, had been there a while before my approach scared them up around 11:30 a.m. They had not cleared a place but just lay down, and the snow barely melted. Beds of the 4 deer were 5-20m apart. Other areas, similar in size and with sides pressed smooth by deer’s body (1 with hairs), had ground bare on the bottom (snow 6 inches deep). In the one with the hairs there were no clear signs of digging, but the others clearly had been dug out.

17JA87, Herrick Lake Forest Preserve. Half an inch of new snow fell the night before. I started tracking in the afternoon, but the tracks were difficult to follow as individual deer and small groups flowed together and apart, anastomosing their trails so that I couldn’t follow an individual for long.

18JA87. McKee Marsh. Better luck. 4 inches of new snow fell overnight, and I was able to follow a single deer for 2 hours, covering about a mile. I was able to stick with him (I believe it was a large buck). I began in the woods near the parking lot, where he followed a winding path, sniffing several shrubs and browsing on a Viburnum (3-lobed leaves and paired red basswood-like buds) and on buckthorn. In one spot where he urinated copiously there were symmetrical shallow hoof marks on either side of his trail, which had the effect of scooping snow into the spot where the urine fell. Then he emerged into open fields E of the woods, wound through a marshy spot, crossed Mack Road, then angled ESE. At one point he suddenly was spooked by a fresh snowmobile track, jumped to the left, then walked across the track and rejoined the trail. Occasionally I had problems when he joined another deer, but by finding every footprint I was able to stay with him until he re-entered the woods and joined 3 other deer. When they split I could not be absolutely sure which he was, but I have about 50% confidence that I followed the right one. He ate more Rhamnus, paused to browse heavily on a young bur oak, wandered up a hill, then joined another galloping deer (and 2-3 others), they all crossed Mack Road onto private property and I could not follow.

Where a buck urinated on his feet, blending tarsal gland secretions with urinary scents

Where a buck urinated on his feet, blending tarsal gland secretions with urinary scents

1FE87. Freshly browsed poison ivy, McKee Marsh. Also white ash within the past 2 weeks. Another deer browsed a woodland rosaceous small tree (probably crabapple), 2 inches dbh. Also a basswood. Twice, it defecated shortly after passing under low branches and browsing a few bites. I tracked the deer until I caught up with it in the cattail marsh north of the woods E of the marsh. It had turned to stand in a well hidden spot to watch me. When I got too close it burst from cover, bounded on through the cattails and through the field on the other side. Tracks in field took more of a bound pattern (not so spread front to back) before and after taller weeds, bounding high to clear them.

Later that same day, following another group of deer, I found where one had bedded briefly, at least, in the wet snow.

21FE87. At Greene Valley Forest Preserve. 5 bucks, still with antlers, traveling together as a group. They were moving fast when first seen, traveling through an open field between hedgerows at around noon. They stopped for a while after gaining a second hedgerow, then slowly moved in my direction (I was wearing a navy blue sweatshirt and dark brown pants, and kneeling). They always had one watching me, often all did, but didn’t run away until much later when I stood and walked. Once, a couple sparred with antlers. Mostly 4-6-pointers.

28FE87. At least 3 deer flushed from area thick with saplings and brush under scattered trees, only 150m from busy highway.

23MR87. Waterfall Glen. Deer dead beside creek near intersection of Cass Ave. and 91st Street. Lying in deer-beaver trail, hind feet in water (fracture of left hind tibia partly healed), head end up on bank. Dead at least a week, ribs largely gnawed away, head gone, muscle and internal organs mostly gone except hindquarters. Other tracks of beavers and dog or coyote (probably latter) nearby.

MY87. New Jersey Pine Barrens. Deer browsing blueberries, a little on oaks.

4AU87. Lebanon State Forest, NJ. 4-5 deer flushed from blueberry undergrowth, bounded until out of sight. Then one snorted a couple of times. I could hear them walking in even steps, without the hitching, explosive quality of a towhee. A little sharper and louder than the sound made by the gray fox seen shortly before. That night, as I walked barefoot in the dark, I came within 10 feet of a bedded deer. The deer detected me, and made a terrific racket getting to its feet. By the time it snorted so I knew what it was, I had taken 2 steps back.

Bumps on the head identify this newly spot-free fawn as a male.

Bumps on the head identify this newly spot-free fawn as a male.

3JA88. McDowell Forest Preserve. Following deer tracks, at least 4 days old. Browsed black maple, as well as several scotch pine branch tips (a broken-off branch, about 0.25 inches in diameter where browsed off; twisting and tearing of adjacent needles. Soon thereafter, browsed from a rose bush (prior to all this eating had followed a slightly sinuous path through maple woods, walking steadily). Tracks probably made New Year’s Eve (day before cold front). Feet compacted very wet snow, so probably late afternoon. Stopped to rub antlers on 0.75-inch dbh maple sapling, on its trunk from 1 foot to 2 feet up from ground, bark removed from one side. Soon thereafter it fell in with 2 other deer. Tracks same age, difficult to distinguish, but I believe the one I’m following has a longer stride. They paused to browse buckthorn, maple, rose (mainly the other 2?). Eventually the 3 bedded down beside a multi-stemmed, branchy silver maple in the midst of a field, about 100m from I-88 (in clear view; dark by then). 2 bedded together, third 10 feet from them. They stayed a little while, but still slushy when they left. They headed for the West Branch of the DuPage River, meandered, browsed, another antler rub. Lots of beds in that area. Tracks turn back along stream toward center of preserve. Lots of deer tracks enter and are present in that area by the stream, but none leave. The deer must cross the stream. I backtracked a bit. Buck had been with the others just before I picked up trail, probably was within sight of them throughout.

9JA88. Most of the needles on that pine branch now are browsed away. Deer commonly cross the river just opposite that grove, though routinely bedding among the yews and other ornamental shrubs between there and the stream. Once across, there is a tall fence paralleling the river and about 30 yards on average from it. The deer remain between river bank and fence. A heavily traveled corridor, a bedding area not far from that crossing site. Opposite the zone where I presume they also crossed the river last week, the fence is low enough for them to jump easily, and they either do that, or go under it at a nearby creek (more common), or continue along fence (also common). But soon comes I-88, and it appears to be a complete barrier on that side. A few cross the river there, a few go around the end of the fence. A very few go under I-88, on west side of river. None have crossed in that presumed crossing zone, but the ice probably has been thick enough to support them for only a couple days, and an open lead about 3 feet across runs along the entire east side along that stretch. That might explain why the tracks were running the opposite direction from last week on the stretches-in-common.

When you hold still and allow a deer to approach, it will stare at you and occasionally stomp a foot as though to startle you into moving and revealing yourself.

When you hold still and allow a deer to approach, it will stare at you and occasionally stomp a foot as though to startle you into moving and revealing yourself.

16JA88. McDowell deer crossed the preserve entrance road just west of the bridge, followed trail steadily between road and river (top of bank). Night before last, not last night. Lost in human and dog tracks, just before widening of area and feeding signs spread out from trail. Well below dam (at least 200m). There signs of much deer activity. Several beds in hill and old-wall area. More feeding and trails (well-used) in even wider area S of there. I flushed a large doe and 2 non-spotted fawns from beds in a pole-tree area a little farther down. They soon circled back around me (to my N). Visible parts: sharp dark horizontal line of back, horizontal white streak of belly cutting through trunks, from side; narrow white outline of tail from back, black nose and eye; brownish cast of fur against gray of trunks (not as distinct).

23JA88. McDowell. Deer recently browsed bur oak sapling. Tracked group of 4-8 deer into NW corner of preserve, brushy area seldom frequented by people, W of beaver pond (dam long, a winding 20-30 yards).

27JA88. Dan Ludwig flew over McDowell and passed on observations of deer: 8 in NW corner, 3 in NE near toll road (both groups west of river, and 6 SE, possibly off preserve.

30JA88. Hartz Lake. Deer trails through woods generally straight, and located to accommodate traveling from one goal to another (goals on either side of woods). Much interdigitation and side-paths abundant around the moist, tall meadows.

29AP88. Pratts Wayne Forest Preserve. Micro pressure releases in one or other toe show where push or pivot was greatest.

1MY88. Warrenville Grove Forest Preserve. Deer ate off tops of several Smilacina racemosa, plus a couple of Alliaria (and other plants, individually removed lower leaves). Not real recently, say 3-8 days ago.

7MY88. Deer tracks, Indian trails of Culver, also ate off tops of a few Smilacina stellata. At Hartz Lake, when one broke a twig loudly, jay responded with “thief” call.

15JL88. Deer heavily eating the Tradescantia at Fulton County museum property, not too long ago. Also eating Seymeria macrophylla.

Antlers nearly grown, but still covered in velvety skin as the bone matures

Antlers nearly grown, but still covered in velvety skin as the bone matures

1AP89. Patch of deer hair on ground in clearing at Hartz Lake. (I also saw some at Winfield Mounds last weekend). Shedding already.

2AP89. Hartz Lake. Deer in groups around clearing (in woods with very little understory) around 9 a.m. A deer snorted. I could just see it through the trees. The nose moved, perhaps a couple inches, but that was the largest motion I could see when it snorted.

13MY89. Hartz Lake, camping. In the dusk, 8 deer came to the prairie area (I was sitting at the opposite edge, by fire). Though basically a doe group, one yearling (small) buck was with them. He was chased a couple times, and a deer struck his back with a forefoot (not a mounting, but a blow). Smaller does still chase after mothers (presumed relationship) to be close to them, when alarmed. I kept still. They saw me, frequently moved heads side to side for parallax.

4JE89. Elsen’s Hill: deer trot pattern showing groups of two prints, 1 foot between prints in a group and 3 feet between groups. Two alternating group types, with front foot of each side ahead of hind foot of other side in that group.

21AU89. Deer tracks, Willowbrook Back 40. Emerged from run, NE corner. Walked down to pond, but stayed above edge (recently arrived, and had drunk from brook?). Nervous. Much starting and stopping, and stomping. Reached a small gulley, then broke into lope, as though the need for the longer step set off a release of nervous energy. 24-inch steps before the lope (toe-tip to toe-tip, measured diagonally). Tendency to splay left front foot and show its dew claws in the lope. While loping, set of 4 tracks 35 inches front to back, groups about 70 inches apart. The tracks were made last night (it had rained the night before last, the tracks made after the rain and after the soil surface had dried). About ten days later: In a hard lope up the hill, the deer showed dewclaws and spread toes on all but the right front. The deer stayed only a couple of weeks. We heard of someone who saw 2 bucks.

2SE89. Tracking deer across screenings trail, McKee Marsh. Stride tended to be slightly longer (23 inches toe tip to toe tip) in tall grass than on path (19-21 inches), except where adjusting stride to clear obstacles. At one point, a hind foot seemed to indicate a turn, falling and pointing to left of the front print, but in fact kept going in the same direction. Response to a disturbance as that foot came down? Implies independence of the 4 feet. Also happened the previous step with that foot.

15SE89. Hartz Lake, edge of open dune. Deer usually pause at edge of clear area before entering it. Shorter strides, and standing.

20SE89. McKee Marsh. A deer, steps 20-20.5 inches on packed screenings trail, became 25-27 inches in tall grass.

Sometimes deer tracks through tall grass are quite clear.

Sometimes deer tracks through tall grass are quite clear.

23SE89. Forest Park Nature Center, Peoria, IL. Deer have been browsing Aster shortii, a species of ridgetops, heavily in recent weeks. This has been their main food within the forest in this period, except for acorns.

24NO89. Hartz Lake. 2 deer beds, SE corner (behind cemetery) in woods. Windy day, saw 2 deer crossing road mid-afternoon, and as I studied tracks on the open dune a doe with a broken or injured right front leg limped past.

13DE89. Hartz Lake. Deer heavily using main north-south trail past couple of days (since snowfall).

16DE89. McDowell Forest Preserve. Patterns of deer activity in west part of preserve much the same as last winter. The only difference is a possible shift from the old home site to the center of the adjacent field in the north part of the preserve. If anything, there is even more concentration of activity to the north end of the preserve than before.

4FE90. Recently shed antler near mouth of Sawmill Creek, Waterfall Glen Forest Preserve.

Late MY90. Hartz Lake. A deer appeared to stomp and snort as a gambit to make me move. Odor and sound spooked them more than small movements.

9JE90. Winfield Mounds. Heavy feeding by deer on goldenrods, past couple of weeks.

Wet forest litter from a recent rain foiled this fawn’s camouflage. Fawn spots form individualized patterns that permit recognition of individuals as long as they last.

Wet forest litter from a recent rain foiled this fawn’s camouflage. Fawn spots form individualized patterns that permit recognition of individuals as long as they last.

30JE90. West DuPage Woods. Fawn moving about and exploring on its own. Still small, but strong. I held still, it slowly moved toward me, sniffing and occasionally stamping like an adult. When mother appeared, and bolted, it ran, too. Tail flag.

13JL90. McKee Marsh. As I was running through the forest, I saw a fawn, approaching half adult size, on the trail ahead. I slowed and quieted my steps. It bolted when I was 10 yards away, and its mother and its sibling, who were close by, bolted as well. Unless the mother gave an audible signal I missed (unlikely, though I was so focused on the fawn that I didn’t see her), she was waiting for the fawn to make the move. If so, she was teaching it to run away from people and to react on its own without depending on her signal.

2JE91. First fawn tracks of the year, Pratts Wayne Woods Forest Preserve.

Doe and fawn. By November, the fawns’ spots are gone.

Doe and fawn. By November, the fawns’ spots are gone.

21DE91. Hidden Lake Forest Preserve. Followed last night’s tracks of a very large deer, sex uncertain but more likely male. Traveled relatively straight lines through open field, but began highly convoluted turnings in a brushier area as it began feeding. Principal (only?) food Geum laciniatum basal leaves, nosed rather than pawed snow to reach them. Ate many. Went out of its way to examine a coyote or dog bed. Bedded, itself, several hours. Note: outward tracks from bed looked older than inward ones. Snow apparently less compactable, or more easily self-kicked back into track, with less smoothly compacted bottom of track and less crisp edges. Wandered and fed more after leaving bed. Defecated several times.

17FE92. Elsen’s Hill (W. DuPage Woods Forest Preserve.). I kept mainly to deer trails, saw 2 deer in a brushy area and, later, in a forest, saw 2 getting up from their beds. I stood still for a while, there, listening, and soon caught movement. Three deer slowly moved into view. Almost certainly the ones I had spooked, a doe and 2 fawns. I kept very still and they approached, the doe doing the foot-stomping test. Sometimes it appears to be largely a nervous expression, others it is very deliberate and calculated, the deer staring hard and keeping its head still while doing so. The fawns kept back. Several times she gradually worked to within 20 yards, then abruptly turned and ran, tail flagging, the fawns doing so as well. On one of these occasions she snorted several times. But I kept still, she didn’t go far, and repeated the process. The closest she ever came was 40 feet. I was wearing the green and black wool coat, standing clear of trees, with a medium density of 2-4-inch dbh trees and a few large ones in that area. The deer finally left for good at the sound of human voices on a trail not too far away, but the deer walked away rather than ran. During all of this there were occasional crows and squirrels seeing me and vocalizing. The deer attended the squirrels, but not the crows, starting at the squirrel’s bark and becoming more wary of me.

3OC93. Rock Island Park, Wisconsin. 2 bucks facing one another, heads lowered near to ground, maneuvering antlers. Like arm-wrestlers seeking best grip.

Early in the 90’s I had a season of deer hunting. During a several-day cold rainy period I sat for hours without seeing any deer. On drier days they were active.

Deer visited several times during the 90’s at Willowbrook. Usually they stayed 2 weeks at most, but during the summer of 1997 a couple of them stayed from May into August.

JE99, Kansas, Konza Prairie. A deer snorted and ran as I approached, holding head and nose above horizontal a bit while snorting.

15MY06. Fullersburg. A deer eating Virginia creeper leaves from a ground vine.

During the 3 years my office was at Fullersburg Woods Forest Preserve, I mapped the winter movements of the preserve’s deer. In the winter of 2006-7 there were 4 groups which followed consistent daily routes as shown.

During the 3 years my office was at Fullersburg Woods Forest Preserve, I mapped the winter movements of the preserve’s deer. In the winter of 2006-7 there were 4 groups which followed consistent daily routes as shown.

28AP08. New antlers beginning to grow on bucks (similar stage photographed 3 May last year).

New antlers just starting to grow

New antlers just starting to grow

15SE10. Meacham Grove. While doing herbivory data collecting I saw 3 antlerless deer. One, a fawn that had become spotless, made a persistent effort to nurse from its mother for a minute or so until she pushed it away. The third I believe was another adult doe.

Maple Leaf Miners: Canopy Data

by Carl Strang

Last week I returned to Maple Grove and Meacham Grove Forest Preserves to collect leaf miner data from fallen sugar maple/black maple leaves. Fallen leaves mainly represent what happened in the canopy, and data from them allow me to make comparisons between preserves, between years, and between the understory and the canopy (I had collected understory data earlier in the season).

This year all the leaves had fallen by the time I did the survey.

It was a pleasant day, and I dressed warmly enough that the November weather was no distraction.

In fact, a number of male linden looper moths were flying at Maple Grove. Also known as winter moths, they wait until November to seek mates.

Though the main purpose of the venture was to count leaf mines, I also kept my eyes and ears open for anything else of interest.

I don’t remember noticing this small concrete foundation at Maple Grove before now. It appears to be an old latrine site.

With the leaves largely changed from yellow to brown, leaf mines were easy to see.

Typical leaf litter scene.

I counted 30 leaves at each of 10 randomly selected points on each preserve. Comparisons between canopy and understory counts this year revealed no statistically significant differences at either preserve, except that there were more Phyllonorycter clemensella tent mines in the Maple Grove understory than in the canopy. This species seems more tied to the understory, and seems to be more affected by controlled fall burns of leaf litter. There were no successful burns at either preserve last year, and I suspect that accounts for the statistically significant increase in this species in the understory at Meacham Grove this year. There were no differences between 2010 and 2011 in the canopy for any of the four mine types at either preserve, and there were no differences between the preserves in canopy counts.

Leaf Miners in the Understory

by Carl Strang

Yesterday I reported on one of my herbivory studies at Maple and Meacham Grove Forest Preserves. Today I have the data for the first part of the other study, a decades-long following of 4 leaf miner  genera in sugar and black maples in the understories of the two forests. While attempting to photograph confused ground crickets at Warrenville Grove, I had noticed a high incidence of tent mines, produced by the micro moth Phyllonorycter clemensella.

This photo from Warrenville Grove shows many leaves with one or more Phyllonorycter mines.

Consequently I was wondering if I would find a lot of mines at my study preserves this year. In fact, Phyllonorycter incidences were relatively high in both forests, in 15 percent of understory leaves at Maple Grove and 4 percent at Meacham. Statistically there were more at Maple than at Meacham, which has been true over the years, probably because of more intensive management at the latter site (controlled burning, and culling of maple saplings). Numbers were not different from last year at Maple Grove, but there was a statistically significant increase at Meacham for this species, possibly because there was no burn last year.

The other leaf miners were present in lower numbers that were indistinguishable from last year’s values. The two species of moths in genus Caloptilia, which leave their mines early and construct little cones or boxes in the leaf lobe tips for most of their development, were more abundant at Maple Grove (8 percent incidence) than at Meacham Grove (2 percent of leaves had them). While 3 percent of leaves at Maple Grove had blotch mines of Cameraria saccharella (another tiny moth), none of the 300 leaves in the Meacham Grove sample had any (only one had a mine last year). The fourth mine is distinctive in having a winding linear form.

The linear mine is visible in the lower part of this maple leaf at Warrenville Grove. I have not reared this one; it probably is produced by a caterpillar of the non-native moth Stigmella aceris.

This one was present in low numbers that statistically were indistinguishable between the preserves (8 leaves at Maple, 1 at Meacham). In November I’ll return to assess canopy incidence of these moths.

Maple Leaf Miners, Canopy

by Carl Strang

On Saturday I returned to Maple Grove and Meacham Grove Forest Preserves to complete this year’s measurements of leaf miners in black and sugar maples. Earlier I reported the results for the understory. This time I was looking at fallen leaves to index leaf miner abundance in the forest as a whole. This can be regarded as a measure of these tiny caterpillars in the canopy, in part because the vast majority of leaves grow there and in part because saplings still are holding many of their leaves at this point in the season.

I went to 10 randomly selected points at each preserve and examined 30 leaves per point. The sunny, calm day was good for this as mines can be difficult to see after the fallen leaves have turned brown. I can hold the leaf so the sun shines on each surface, then hold it up so light shines through it.

In the five years that I have taken this measurement I have found few differences between canopy and understory leaf miner abundances. The most common difference is a lower incidence of Phyllonorycter tent mines in the canopy than in the understory, and such was the case this year at Maple Grove. Also at Maple Grove, Caloptilia boxfolds were less common in the canopy than in the understory this year.

All four genera of these tiny moths were in low numbers in the canopies of both preserves. The most abundant were Phyllonorycter at Maple Grove, where I found tent mines on 15 of 300 leaves, or 5%. That was the only species which produced a statistically significant difference between the preserves. In general, populations have been low since I began measuring canopy leaves, so I have yet to see a consistent pattern of differences. The only complete miss this year in understory and canopy combined was an absence of linear mines (probably produced by the non-native moth Stigmella aceris) at Meacham Grove (one turned up in the canopy sample there last year).

I have been interested in the effect of the more intensive management at Meacham Grove on insects and plants I am studying in these preserves. On Saturday I noticed that a burn had been attempted yet again at Meacham.

As you can see, the line of burning fuel dripped along the edge of the trail (which serves as a firebreak) did not take. There still is time for another attempt this fall.

Maple Leaf Miners, Understory

by Carl Strang

In addition to the trailing strawberry bush (reviewed yesterday), I looked at leaf miners on understory sugar and black maples at Maple Grove and Meacham Grove forest preserves last week. As was the case with the other study, I was interested in the potential impact of controlled burning on the populations of the tiny moths whose caterpillars mine the leaves. Even after a year, the burned areas still had essentially no leaf litter.

Unburned areas at Maple Grove, and in a separate, off-study-area forest in Meacham Grove Forest Preserve, had plenty of litter remaining.

The upshot, though, is that I cannot identify any impact of that fire on leaf miner populations. This is not because they are all high, but rather because the four genera of miners have been consistently low at Meacham Grove for 15 years, now. This year, likewise, maple leaves were very clean at Meacham.

That result, I suspect, is more from the sustained intensive management at Meacham Grove over the years, with greater removal of understory maple saplings and more frequent and extensive burning. This is consistent with Meacham Grove’s forest having more of an oak component, a sign that it was exposed more to fire in its early days, fire that would have limited maple reproduction and dominance. The differences I have observed between the two forests in understory leaf miner populations thus may reflect a historically significant difference in the ecologies of the two preserves. Certainly the management at Meacham has produced an increase in botanical diversity of forest floor plants there.

In three of the four leaf miner genera, understory populations were higher this year at Maple Grove than at Meacham Grove. At Maple Grove, Caloptilia were present on 8% of understory leaves (2% at Meacham), probable Stigmella were on 3% (0% at Meacham), and Phyllonorycter were on a whopping 19% of understory leaves (0% at Meacham). The difference in Cameraria blotch mines, on 2% of Maple Grove leaves and 0% of Meacham Grove leaves, was not statistically significant (for more on these insects, go here). Though I did not take measurements, Phyllonorycter tent mines to the eye were much more abundant in the unburned, less managed forest block at Meacham Grove, and thus resembled Maple Grove.

At Maple Grove, two of the four insect groups increased over last year. That 19% figure for Phyllonorycter in fact is the highest since before 1996, and it is the fifth time that population has occurred on more than 10% of leaves in that period. The median annual value in those 15 years has been a healthy 6%. Caloptilia likewise have stayed strong, with a median matching this year’s value of 8%. This year’s frequency of 3% likewise is the median value for Maple Grove (probable) Stigmella. Cameraria has stayed low, with a median of 2% (also this year’s Maple Grove value). The respective medians for Meacham Grove have been 1%, 4%, 1%, and 0%. All of this discussion has been about the understory. The forest canopy may produce different results, which I’ll investigate in November.

Canopy Leaf Miners 2009

by Carl Strang

Recently I reported the results of my survey of black/sugar maple leaves in the forest understory at Maple Grove and Meacham Grove Forest Preserves. Each year I measure the incidence of four groups of leaf miners on those trees at those preserves, continuing a study I began in the 1980’s. Having found very few leaf miners of any type on the low saplings in September, I returned in November to gather data from fallen leaves, nearly all of which come from the canopies of mature trees.

Linear mine on a fallen leaf

As in the understory, canopy leaves had relatively few leaf miners. The highest incidence in any 300-leaf sample was 11 leaves bearing blotch mines of Cameraria caterpillars at Maple Grove. In comparisons between canopy and understory incidences, none were statistically significant. Comparisons between canopies of the two study areas likewise revealed no differences.

I also compared leaf miner incidences between 2009 and 2008. The only statistically significant changes were decreases in Caloptilia boxfolds at Maple Grove, both in the understory (a drop from 42 to 9) and in the canopy (a similar drop from 32 to 9).

It is worth noting that I found low numbers of all four mine types at both preserves this year.

Cameraria mine in a fallen leaf

This is the first time since 2006 that the sample included Cameraria at Meacham Grove.

Understory Leaf Miners 2009

by Carl Strang

In a series of posts last winter I outlined my results to date in a study of several species of leaf mining moth caterpillars that occur on black/sugar maples at Maple Grove and Meacham Grove Forest Preserves. This study, begun in the 1980’s, continues to be worth pursuing; I put in a total of about one full field day per year.

ACNI tent mine b

Tent mine formed by Phyllonorycter larva

One aspect of the study is a comparison of leaf miner occurrence in the canopy versus the understory. Today I’ll report this year’s results for the understory, having gathered those data in September. The story can be told simply, as I found very few leaf miners of any kind at either study area. Out of the 300-leaf samples from each preserve, the greatest number of leaves bearing a leaf mine type was 9 (Caloptilia boxfolds at Maple Grove). That number itself represented the only statistically significant change from 2008, having dropped from 42 leaves in last year’s Maple Grove sample. In comparisons between study areas, only the linear mines which I believe are produced by Stigmella showed a difference. Technically, however, the 8 leaves at Maple Grove versus 0 leaves at Meacham do not meet the criteria for the statistical test I use.

Maple leaves 19SEb

So in the understory the maple leaves were about as clean as I have ever found them. I’ll go out to collect the canopy data soon.

Tortricids

by Carl Strang

Last winter over an intermittent series of posts I summarized some of my research on leaf-eating insects in DuPage County forests. Most of that work was in the 1980’s, but I have continued a couple of studies to the present day. One of those is following leaf miners of sugar/black maple leaves . In my study forests I found that the maples host a long list of leaf consumers. Each year the parade of them begins with the tortricids. Here is the adult stage of one of those moths, Choristoneura rosaceana.

Tortricid adult b

The wingspan of this mounted specimen is three-quarters of an inch. Its small larva looks like this:

Tortricid caterpillar b

The caterpillar bites through the major veins of the maple leaf at the base, so that the leaf wilts.

Tortricid collapsed leaf b

This presumably cuts off the leaf’s ability to produce defensive chemicals, and also provides a shelter that protects the caterpillar from birds, which focus on more easily gleaned prey. When the caterpillars become abundant, their numbers get knocked back by parasitic wasps. I found that the wasps’ eggs are readily visible in the parasitized caterpillar.

Tortricid parasitized b

This year I decided to go back to my study areas and see what the tortricids are up to. The bottom line answer is, not much. There were a few, but in my random samples of 20 maple saplings per preserve I found only one tortricid caterpillar, at Maple Grove. There were none at Meacham Grove, though I did see a few on saplings outside the sample. This compares to the peak year of 1982, when 63 percent of maple saplings at Maple Grove and 88 percent at Meacham Grove hosted at least one tortricid caterpillar. I plan to continue taking this measurement in coming years.

Incidentally, while sampling Meacham Grove I checked out the trailing strawberry bush (Euonymus obovatus) plants to see if they have ermine moth caterpillars this year (I reviewed this study last winter). The plants all were clean and green.

EUOB 7JE09b

At one point I looked down and saw this.

Campaea perlata 1

Sticking out beyond the edges of the enchanter’s nightshade leaf were moth wingtips. I tried holding the camera underneath and taking a photo without looking through the viewfinder.

Campaea perlata 2b

The pair of moths apparently had mated the previous night and were waiting out the day. Having acquired my contingency photo, I carefully inverted the leaf. The male moth took off, but I was able to get a clearer shot of this beautiful pale green, leaf-mimicking Campaea perlata female.

Campaea perlata 3b

On the way out of Meacham Grove I got the opportunity to photograph this mourning cloak caterpillar.

Mourning cloak caterpillar b

All in all, this was an enjoyable return.

Leaf Miners 3

by Carl Strang

 

A few weeks ago I introduced my ongoing study of leaf miners in maple leaves, moths so tiny that their caterpillars live between the upper and lower surfaces of leaves. I left a few questions unanswered, and I want to return to what I have learned so far in attempting to answer them.

 

Cameraria saccharella adult specimen

Cameraria saccharella adult specimen

 

 

  • These two study areas are separated by many miles of suburbs. Do the populations of the leaf mining species go up and down together on the different study areas (which might reflect responses to climate as it varies between years), or do they fluctuate independently (which might indicate biological regulation of populations)?

 

Numbers of these insects have been so low since my return to this study in 1996 that drawing conclusions is problematic. However, there have been several occasions when proportions of leaves with one type of mine have been significantly higher on one preserve than the other. In the case of the boxfold species, Caloptilia, there were appreciably more at Meacham Grove in 1996, and at Maple Grove in 2004 and 2008. The tent-mine-forming Phyllonorycter has consistently been more abundant in Maple Grove samples over the years, and this difference has been statistically significant several times. Other miners have been present at such low levels that for all practical purposes they have been the same.

 

  • How does restoration management practice affect these organisms? These maples are the main target of management in these forests, because they are so shade tolerant that they can push out all the other plant species over time. Once they were kept in check by the rare fires that reached even the moister woodlands. Now, selective removal of maple saplings and controlled burns are used to restore higher diversities of other plants, of the many insects that depend on those plants, and the consumers of those insects.

 

The potential impact of management on these leaf miners has to be speculative, as little is known about their natural history. Meacham Grove has been managed more intensively than Maple Grove, though both preserves have received some attention. Is this why Phyllonorycter has remained so low in numbers at Meacham? Though the differences are not statistically significant, in almost every year the numbers are slightly smaller at Meacham than at Maple Grove for Cameraria blotch mines and (presumed) Stigmella linear mines, too.

 

A controlled burn of the leaf litter at Meacham Grove in the fall of 2007 was followed by practically no leaf miners of any kind in understory maples in 2008, but their numbers were so low in 2007 that any connection to the burn would be hard to argue. If the moths overwinter in that litter, the burn may have knocked them down enough that I may see very low numbers there for several years.

 

  • Do the moths have the same impact on the canopies of large trees as they have in the understory?

 

All of my 1980’s focus was on saplings in the understory. In recent years I have attempted to compare the understory and canopy trees, first by looking at leaves on the branches of large trees that could be reached from the ground, and second by measuring incidence of mines on fallen leaves (the vast majority of which come from the canopies of the larger trees; also, the larger trees lose most of their leaves before the saplings do, so I can improve the distinction with careful timing).

 

In 2005 I looked at leaves on low branches of larger trees, and found no difference in any of the leaf miners from what I measured in understory plants. This is not necessarily a trivial comparison; large trees have greater resources with which to create chemical or physical defenses, and might have had fewer miners.

 

In 2006-8 I have been looking at fallen leaves as a measure of leaf miners throughout the forest. After three years I have only tentative conclusions. It is beginning to appear that tent-mining Phyllonorycter prefers the understory, supporting the possibility that management removal of maple saplings has had an impact on that species at Meacham Grove (some do live in the larger trees, however, and the number of leaves in those trees is so huge that a 1% incidence level still represents a lot of moths). The other miners have not shown differences between canopy and understory, though it should be said that blotch-mining Cameraria and linear-mining presumed Stigmella are at such low levels at Meacham Grove that nothing really can be said about them from these few years.

Do the Leaf Miners Avoid One Another?

By Carl Strang

 

Yesterday I described several species of tiny moths whose caterpillars mine the leaves of black/sugar maples in DuPage County, Illinois. Today I want to review some of the results of my inquiries into this system (by “system” I mean a group of interacting species in a particular environment) since 1983.

 

In the mid-1980’s these species all were abundant, and collectively they were removing a significant portion (in 1984 more than 20%) of the maples’ photosynthetic tissue in understory plants. We might expect that in such a situation it might benefit them to avoid one another. There are mathematical methods, called statistical tests, that allow us to say whether the co-occurrence of these herbivores on leaves is taking place randomly (no interaction evident), whether they may be avoiding one another (co-ocurrence on leaves is less than one would find in a random situation), or whether they are attracted to one another or at least to the same leaves (co-occurrence greater than in the random case).

 

acer-leaf-miners-b

 

I made these comparisons in 1984, 1985, and 1986. If there are any interactions between these leaf miner species, we would expect to see the same result showing that to be the case in each year. With four mine types, there are 6 ways any two of them can form a pair for comparison in a given year. That makes 18 statistical tests over the three years. Out of these 18, only four showed a statistically significant departure from random co-occurrence. However, only two of the four involved the same two species, Caloptilia and presumed Stigmella in 1985 and 1986. Those same two species gave a random result, however, in 1984, the year when leaf tissue loss was highest and presumably there would be the greatest benefit from avoidance. On the whole I had to conclude that these species are interacting weakly if at all.

 

This seems puzzling, but I have a guess as to why it’s the case. When I returned to this system in 1996 I found the populations of leaf miners very low compared to the 1980’s. Only in the case of Caloptilia at Meacham Grove did more than 10% of the leaves have one or more of these insects. Populations have remained at or below these levels ever since. It’s beginning to look like the high numbers of the mid-1980’s were unusual, so that there has not been selective pressure to benefit individuals with avoidance behavior.

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