Vernal Pond Adventures
The largest of our vernal ponds in early April.
Once again I’m sitting beside our mountaintop vernal pond and wondering if this will be the year the wood frogs will make it out of the pond before the water disappears. A wood frog’s life span is about seven years, and for six years the pond has dried up before the wood frogs’ have fully developed. Some years their eggs are left high and dry; other years their tadpoles are.
A vernal pond is a temporary, fish-free wetland that fills in late winter or early spring and dries out by early summer in a good year. This pond is only several yards across and several yards long, depending on rainfall, and, unlike the tiny, 6-foot-wide pond at the base of First Field, I can’t get close enough to watch the courtship and mating of the frogs. I can hear their quacking calls, though, and I enjoy watching a wide variety of wild creatures that visit it even when I’m sitting quietly beside it, my back against an oak tree.
I find it incredibly peaceful to watch the pond as it reflects the trees in its still water. But this early March day a skim of ice over it glitters in the sunlight. Its surface has a medley of half circles and triangles artistically rendered by the ice-maker overnight.
On the thirteenth of March, as I near the vernal pond, circles appear in the water. I wonder if they can be disappearing wood frogs. I study the still, dark water and spot one small mass that I look at through my binoculars. A golden eye returns my gaze. I move closer and see a male wood frog stretched out in the water. Next to him is a stick with two clumps of wood frog eggs clinging to it. This unusually bold wood frog dives into the water but quickly resurfaces. Since I am still standing there, he sinks back under the water.
The vernal pond has already contracted, and I hope that the dark clouds rushing across the Allegheny Front will drop some rain on us and fill up the pond. But it doesn’t happen. Nevertheless, two days later, I find two wood frog egg masses in different areas. The gelatinous, fist-sized blobs contain several hundred eggs with black embryos.
By the 22nd of March, I count four separate egg masses, but the vernal pond is still shrinking. If the rain comes soon enough, the eggs may survive. And come it does, raining hard from 1:00 a.m. until mid-morning on March 24, filling up the vernal pond again.
The vernal pond in mid-March.
It’s almost a month before I return to the pond. At the beginning of April, while hiking on Sapsucker Ridge with my sixteen-year-old granddaughter Eva, she steps on a branch and I trip over it, my left leg landing hard on a pointed rock. Nothing is broken or fractured the doctors tell me, but my leg and foot swell up and turn black and blue. I have, after all, injured my tibia, the bone just below my knee. After days of being veranda-bound and more days of slow, short walks, I finally make it back to a vernal pond seething with insect life, most notably water striders walking atop the water and looking for mosquitoes resting on the water just after they have emerged from their “wriggler” larval stage.
Various species of diving beetles also swim in the water on the hunt for invertebrate and vertebrate creatures, including the wood frog tadpoles. I have always marveled at how these insects find a vernal pond, especially this one, isolated on a mountaintop half a mile from the nearest stream and that one intermittent near its source. Apparently, they are able to fly to it from such water. But some species of diving beetles actually overwinter in the basin formed by a dried up vernal pond.
The wood frog eggs have long since disappeared from sight, colonized by the symbiotic algae Oophila amblystomatis, which turns them green. It’s been cold most of the month, delaying the hatching of the eggs. But near the pond I stop to admire the patch of spreading spring beauties, the only place they grow on our property. This is an open, mixed-oak forest close to our neighbor’s logging operation that took place several years ago. Not much has regenerated and the vernal pond is not as shaded as it used to be.
It’s now the fourth of May and torrid summer weather has returned. I practically stumble over a porcupine as I approach the vernal pond and send the creature scrambling up a large red oak tree. The vernal pond is a veritable tadpole soup—tadpoles by the dozens wherever I look, floating near the surface to warm themselves up now that the trees have leafed out and are shading the pond. They need the solar heat to develop quickly into frogs before the pond dries up. First they graze on the symbiotic algae still clinging to their gelatinous cradle, and then they feed on algae and leaf material on the pond’s bottom. They also may feed on each other, those that hatched first preying on the latecomers.
Three days of hard, cold rain follow, and once again the vernal pond is overflowing and seeping over into a series of wallow-sized pools. My pond-watching becomes an almost daily discipline as I sit and watch the tadpoles eating, swimming, and basking in patches of sunlight. In mid-May I hear clucking as a hen turkey circles behind me. Maybe she is hoping to catch some tadpoles for brunch.
Water striders
Often the tadpoles join in aggregations of ten on a submerged stick. Then there is a sudden flurry and they separate, but in a few seconds they gather together again, performing their own watery tadpole ballet. In addition to basking in the sun, perhaps they are finding refuge from predators in a crowd like flocks of birds do.
By the twentieth of May a few of the larger tadpoles are developing back legs. I sit close to the water and watch as the tadpoles continually surface to feed on the detritus floating on the water, then submerge, each tadpole swirling the water into a circle. I try counting the circles to figure out how many tadpoles still inhabit the pond, but the confusion of circles quickly confuses me. Instead, I settle back and enjoy the ambiance of the pond and surrounding woodland having long ago learned to tune out the occasional train whistle and the constant traffic noise on Interstate 99 at the base of the ridge.
A mourning dove sings without ceasing. Red-eyed vireos, eastern wood pewees and a scarlet tanager frequently add their songs to that of the doves. Water striders skate along the water. A common green darner dragonfly buzzes over the pond. Then an American crow flies in like a kamikaze fighter plane, veers when it sees me, and silently retreats.
There are more days of rain and again the pond overflows. The pond water is so dark that I can’t glimpse the tadpoles, but dozens of circles that gradually subside as I sit in front of the pond indicate their presence. Sitting beside the pond, a sudden nearby gunshot startles the tadpoles as much as it startles me. Not only do they have sharp eyes but sharp ears too.
Near the end of May, I’m serenaded by a robin and scolded by a hairy woodpecker while I sit beside the pond. I also see a dark-eyed junco, which should have been breeding farther north on the Allegheny Front or beyond by now. A mourning dove flies in to catch insects from the pond and goes off in a flurry when it realizes I am there. A black-and-white warbler sings. Chipmunks scold. Mosquitoes that probably have hatched in the pond circle me and force me to move on after I catch a glimpse of a few more tadpoles with back legs.
My vigil continues in June. By then, I wonder if those tadpoles will ever change into bandit-masked wood frogs. On June 8 many heads pop up from the water and stay up even though most tadpoles still have tails. Two male robins hold a song fest while a female chases all comers to the pond as her spotted youngster bathes. Later a tufted titmouse takes a bath. Chipmunks chase around the pond and one scampers up to me, pauses at my feet to look, and then continue its race with its rival. A pileated woodpecker pounds on a nearby tree trunk.
Wood frog in mating season (in the tiny, spring-fed pool at the bottom of First Field)
All the while a pleasant breeze blows, keeping biting insects away. The pond is slowly shrinking, but it is still a bathing and watering hole for birds and mammals alike.
The following day I spend another session at the vernal pond serenaded by the same two robins. Little mouths surface to catch detritus spread atop the pond, and once I see a tiny froglet hopping over a small section almost as if it could walk on water. Froglets are supposed to be between a half and 7/8th of an inch when they metamorphose. Their watery life is ending and none too soon.
A chipmunk approaches me with much trepidation, and when I don’t move, it goes to the pond and drinks. Then it scampers off.
Suddenly, the robins begin high octane scolding as if, after half an hour, they finally notice me. On and on they scold, but at last they subside.
When I am too stiff to sit any longer, I get up and walk back to the field path. There I find an enormous pile of fresh bear scat that wasn’t there before. It looks as if the robins were scolding a bear.
A couple days later, as I’m sitting by the pond, I hear crashing in the woods that sounds like a bear. Sure enough, one approaches the pond, and I ponder my position. It’s obviously hoping for a drink and doesn’t see or scent me. At last I stand up, and the bear looks up, sees me, and flees.
The vernal pond continues to fill every time it rains, and slowly the froglets depart, although I don’t see them. But there are fewer circles in the water, less little heads surfacing, every time I visit. How wonderful that after so many springs when the pond dried up too soon, our aging population of wood frogs will finally get some newcomers. The young frogs will spread out, traveling up to several hundred meters in all directions, making new homes in the leaf litter, and preying on a variety of arthropods.
But even as the pond shrinks and the froglets leave, I still seek quiet time beside it. One day, late in June, I encounter an eastern box turtle, floating in a couple inches of water, its eyes closed. At first I think it is dead, but when I touch it, it opens its eyes. Later, I learn that eastern box turtles like to soak and feed in vernal ponds.
Wood frog found under a rock in Plummer’s Hollow Run in September
On another day, two doe wander past me and water at the pond while I sit a few feet away. Then they continue on their way. They never do detect my presence.
I can only wonder how many other wild lives are impacted by this small pond. Even though knowledgeable foresters will steer logging operations away from such places, most loggers either don’t know or don’t care about such refuges. Or they begin their logging operations in the fall when the ponds are dried up and they don’t recognize them for what they are.
My own life has been enriched by our vernal pond this water-full spring. Even after it is completely dried up, in broiling hot, droughty July, I wander back to sit under the oak shade. Where have all the wood frogs gone?
One day, on my daily walk, an adult wood frog hops across my path.
“There you are,” I say out loud as it hops quickly out of sight.
Black-legged Ticks
This marks the 20th anniversary of my column for the Pennsylvania Game News. The first appeared in January 1993 and concerned the Carolina wren. Thanks for reading!
—Marcia
Last January I walked along the Black Gum Trail. Since our son, Dave, constructed the trail halfway up Laurel Ridge, back in the 1990s, I had never been able to take the trail in winter. Usually, it was deep in ice and snow as was our north-facing hollow road. But on that mild day there was not a smidgeon of ice or snow on the trail or road.
I neither saw nor heard any creature despite the warm day. The long-promised sun was trying to shine through a matrix of puffy, white clouds drifting past patches of blue sky. At dawn it had been 34 degrees and breezy, and the thermometer had been slowly rising all morning.
Then, as I descended the trail, I glanced down at my pants and socks and pulled off seven adult black-legged ticks. I could hardly believe it. I had considered winter to be tick-free on our mountain. Usually, they spend their winters buried under leaf litter that should be covered with snow. But they are tough creatures, and as soon as it warms up they are out and about. At that time the adult females are not carrying Lyme disease because they had had their last blood feeding on white-tailed deer. Some even winter on the deer.
But, as Dr. Richard S. Ostfeld of the Cary Institute of Ecosystem Studies in Millbrook, New York says, don’t blame deer if you get Lyme disease. The immune system of deer kills the bacteria that cause the disease.
“We don’t know why,” Ostfeld says, “but the deer immune system clears the infection. When they get bit, they wipe out Lyme. Deer play a tremendous role in suppressing adult ticks from spreading the bacteria.” He also dislikes the name “deer tick” and prefers “black-legged tick.”
White-tailed deer in Plummer’s Hollow (photo by Dave Bonta)
After all, like any arachnid to which ticks are closely related, the nymphs and adult ticks have eight black legs. But the larvae only have six. The larvae hatch from the several hundred to a few thousand eggs each female adult tick lays in spring. She then dies. Both the larvae the first summer and the nymphs the second summer feed once on a mammal and prefer white-footed mice, although they will feed on other small mammals or birds if they can’t find a mouse.
And it is white-footed mice that are the real culprits. They can get the Lyme disease bacteria and pass it on to the ticks even though the bacteria don’t seem to sicken them. Because nymphs are so small, no larger than a poppy seed, they are liable to bite and never be detected during the three to four days they need to take their blood meal. At least 70% of Lyme disease cases are from those nymphs that do not look like the black and reddish-brown adult female ticks. Instead, they have dark heads and bodies that appear to be translucent. Adult male ticks, which don’t feed but will attach to a host when searching for a female to mate with in the fall, are either black or dark brown.
Entomologist Thomas Say named the black-legged tick — Ixodes scapularis — back in 1821. But the first known case of Lyme disease wasn’t identified until 1975 when several children in Lyme, Connecticut were diagnosed with juvenile rheumatoid arthritis. It turned out to be what later was named Lyme disease. In 1982 scientist Willy Burgdorfer isolated the bacterium causing the disease, and it was named in his honor Borrelia burgdorferi.
Scientists also thought that a new species of tick carried the disease and named it Ixodes dammini. It was only later in the 1990s that they realized the tick transmitting the disease had been around and named long ago. But they did recognize that the tick belonged to the family Ixodidae, the so-called hard ticks. They have a hardened plate called a scutum on their idiosoma region, which is a specialized part of a tick’s body that expands to hold its blood meal.
White-footed Deermouse (Peromyscus leucopus) by J. N. Stuart (Creative Commons BY-NC-ND license)
Like ticks everywhere, the nymphs and adults climb a shrub or blade of grass, hold out their forelimbs, and wait for a victim to brush past. They also lurk on fallen logs, tree trunks, or even on the ground, especially the nymphs which can’t climb as high as the adults. Since they arrived on our mountain, about six years ago, I no longer have the pleasure of sitting on my hot seat on the ground, my back against a tree, watching the life of the forest. They even reach me on our benches unless I pull my feet up on to them.
Ticks have a Haller’s organ on each foreleg with spiny indentation packed with sensors and nerves capable of picking up a breath of carbon dioxide, heat, sweat, or even vibrations from your footsteps. So no bird or mammal can escape their sudden lunge. As I’ve discovered, the small huckleberry shrubs on Laurel Ridge Trail and the grasses of First and Far fields, are ideal “questing” posts for ticks, as well as the underbrush in our forest off the trails where I rarely venture anymore.
Once a tick arrives on its host, it probes around for a soft, bloody site to attack, often in private crevices. Normally, you won’t feel a thing. As David George Haskell writes in The Forest Unseen, “I suspect they charm our nerve endings, taming the cobralike neurons with the hypnotic music of their feet.”
The tick presses its mouthparts into your flesh and saws an opening. Then they lower a barbed tube, called the hypostome, to draw out blood. Because it takes several days to get a full blood meal, it cements itself to your skin with a glue-like material called “attachment cement,” which is why a tick is so difficult to remove.
During the first 24 hours it is attached, it is harmless. But later, when it is full, it takes water from your blood into its gut and spits it back into you, which is when it can transmit Lyme disease or two other diseases — babesiosis and anaplasmosis. The parasite Theileria microti causes babesiosis and Anaplasma phagocytophiolum causes anaplasmosis. As many as 2 to 12% of Lyme disease patients will have anaplasmosis and 2 to 40% babesiosis. This complicates the diagnosis and treatment sometimes because the tick might transmit one or the other or both diseases and not Lyme to a patient. In rural New Jersey, for instance, the Center for Disease Control studied 100 black-legged ticks and discovered that 55 of them had at least one of the three pathogens.
Black-legged tick by Jerry Kirkhart (CC BY license)
Both babesiosis and anaplasmosis have flu-like symptoms similar to those of Lyme disease but without the telltale bull’s-eye rash. Some folks don’t recognize or even have symptoms of babesiosis, yet they can pass it on to others through donated blood. So far, Pennsylvania seems to be almost free of those two diseases, but they are more prevalent in New York and New Jersey. Unfortunately, it is probably only a matter of time until these diseases increase in the commonwealth.
Last year was supposed to be especially high in Lyme disease cases. That was because in 2010 there was a bumper crop of acorns, followed by 2011 when there were practically none. Dr. Ostfeld, forest ecologist Dr. Charles D. Canham, and colleagues at the Cary Institute first worked out the connection between the amount of acorns and the population size of white-footed mice. In abundant acorn years mice numbers soar but they crash when the acorn crop fails. According to Ostfeld, that leaves a large number of infected ticks looking for hosts. Without the mice, they are after us instead.
At least one hunter friend of ours contracted Lyme disease last June. Although he did get the rash, he never saw the tick. I suspect it was a nymph that bit him. He also listed four places where he could have picked up the tick — turkey-hunting at our place, at a friend’s country property, and on his own country property, or his backyard at the edge of Altoona.
If Ostfeld’s research is right, his backyard was the most likely habitat. In a paper for Conservation Biology Ostfeld and other colleagues entitled “Effect of Forest Fragmentation on Lyme Disease Risk,” they wrote, “Our results suggest that efforts to reduce the risk of Lyme disease should be directed toward decreasing fragmentation of the deciduous forests of the northeastern United States into small patches… The creation of forest fragments of 1-2 hectares should especially be avoided, given that these patches are particularly prone to high densities of white-footed mice, low diversity of vertebrate hosts, and thus higher densities of infected nymphal black-legged ticks.” Given both the size of our forest and the diversity of vertebrate species, we should have less Lyme disease here.
Berberis thunbergii – Japanese Barberry berries by Virens (CC BY-NC-ND license)
On the other hand, another study by Tom Worthley and other researchers at the University of Connecticut Forest in Storrs claims that eliminating the invasive Japanese barberry shrubs (Berberis thunbergii) will help control the spread of Lyme disease, anaplasmosis, and babesiosis because white-footed mice favor the barberry’s habitat.
“When we measure the presence of ticks carrying the Lyme spirochete we find 120 infected ticks where barberry is not contained, 40 ticks per acre where barberry is contained, and only 10 infected ticks where there is no barberry,” Worthley says.
Unfortunately, our neighbor’s old 100-acre property that we were able to purchase only after it was poorly logged, is filled with Japanese barberry and other invasives. It’s also moved into the edges of our fields and even into the edge of portions of our older forest. Eliminating all of these bushes will take many manpower hours. But our caretaker hopes to experiment with a few of his own ideas for removing them over the next several years.
In the meantime, I’ll continue to follow most of the suggestions for avoiding tick bites, including super vigilance of my clothes and body, even in winter, when I take my daily walks.
Marcia with golden eagle (photo by Todd Katzner)
Marcia Bonta is the author of nine books and over 300 magazine articles. The blog portion of this website includes her popular “Naturalist’s Eye” column from Pennsylvania Game News, reprinted here on the 1st of each month. Unlike typical blog entries, these columns are written months in advance, usually about things that happened during the previous year. Read more…
