Signs of Winter 1: Night Sounds

Photo by D. Daniels, Wikimedia Commons

As winter settles in around us I really regret having to abandon our ritual of long, evening sits out on our deck and the necessary nighttime (and daytime) closings of the windows of our house. These actions, which are absolutely necessary considering we live in a site with a real winter, seal us off from all of noises and all of the wonders of the nighttime ecosystem around us.

Late last December I took my dog, Izzy, out for a post-dinner stroll around the yard. It was about 7 pm and it was a fairly mild, clear evening with an almost full moon. While we were out I heard a familiar “Who … Who” call of a great horned owl coming from the tall blue spruce tree in the front of my house. I took the dog in and gathered up my family (everyone was home for Christmas) so they could come and listen. The “who’s” were still coming loud and regular, and we angled ourselves relative to the spruce tree so that we could see the silhouette of the calling owl against the moon-lit sky.  Then, we heard another great horned owl up in the bare poplar trees far across the street answering the first!  We went in for the binoculars and found the second owl perched up on one of high, bare branches. The four of us (Deborah, my daughter Marian and my son Joe and I) stood out there for nearly an hour listening to the “conversation” between these two owls.

Great horned owls mate in the winter, and I assume that these were a potential mating pair working out the details of a closer encounter (after all of these noisy people went away!).

A great horned owl on You Tube!

Photo by D. Daniels, Wikimedia Commons

We also have eastern screech owls around my house. We usually hear them in the summer and in the fall. It is unlikely that they would be calling on the same night as the great horned owls since screech owls could be prey for the much larger great horned owls. The screech owl’s call is a very distinctive, extended trilling song that has a number of variations and functional adaptations. Screech owls also have sharp, barking-like calls that they use when they are disturbed or upset, and harsher, descending “whinnies” that they use to mark their territories. You seldom see screech owls although they are very common and are very tolerant of people. Their camouflage is excellent and they spend most of the daylight hours well concealed in their tree holes or wedged up against the concealing bark of a tree. Their calls, though, fill the night almost all year round.

An eastern screech owl on You Tube!

The transition of summer to fall for me is marked by the change of insect night sounds. The late summer cicadas give way to the chorus of crickets that chirp away throughout the night. I never seem to notice, though, exactly when the crickets stop chirping. Winter shuts them down probably around the same time as it drives us in from our deck and forces us to close up our windows.

Crickets on You Tube!

USDA Photo, Public Domain

Last night right before bedtime, I took Izzy out front to get her to urinate one more time before bed. Our front yard, especially at the edge of the road, is a highway for all of the neighborhood dogs and cats (not to mention any passing raccoon, possum or skunk), and their scents almost always stimulate Izzy to add some of her own urine to the communication mixture. Last night, though, a young buck was out in the yard munching on the remains of the day’s sunflower seeds in my bird feeder, and he was reluctant to give up his nighttime snack. The buck retreated across the street and repeatedly snorted at me, telling me to go back inside. He refused to run away (the deer have become very familiar with me and, often, they won’t even run if Izzy makes a dash toward them (she never gets very close, though. She recognizes the very large size difference!)). The buck continued to snort at me and I ended up taking Izzy out into the fenced side yard (where, by the way, she refused to pee).

A deer snorting on You Tube!

Photo by K. Laubenstein, USFWS, Public Domain

One night this fall we heard a scream that seemed to be coming from our orchard just outside of our side fence. It was a blood curdling sound that gave me the chills and made Izzy crawl into a corner of the living room. I went out on the deck with a flashlight and heard the scream a few more times, but I could not see the source. From the sound, though, I was pretty sure that it was a red fox. I just wasn’t sure why it (and I am pretty sure that “it” was a “she”) was screaming. Red foxes (especially the vixens) make astonishing noises during mating (but that occurs in the spring) or when they are being attacked or under severe distress. I wasn’t sure if there was a territorial dispute going on among our foxes (we have seen them running across our field at dusk) or if something like a coyote (we have seen a few of these nearby, too) was threatening it. After a few minutes the screaming stopped, and checking the area the next morning I could find no evidence of any serious altercations. Maybe the screaming worked?

A red fox screaming on You Tube!

Photo by Mingo 123, Pizabay

Raccoons are terribly impressive animals. I have seen raccoons stare down a 90 pound lab who was an absolute killing machine when it came to animals like woodchucks. Even the lab, though, recognized that raccoons were not something to mess with. Raccoons are nocturnal foragers looking for almost anything from spilled bird seed to grubs and worms to garbage to fill them up. Raccoons are also, apparently, a bit antagonistic with each other especially if food or living space is in short supply. We hear tussling raccoons especially in late summer when the rapidly growing kits have become increasingly independent and self-sustaining. We hear this a lot in August!

Raccoons fighting on You Tube!

Finally, a soft quiet incredibly welcome sound of Spring: the spring peepers! A nice way to start Signs of Winter, thinking about the Spring that is not too far away!

 Spring peepers on You Tube!


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Signs of Fall 13: Lake Erie is Green (but not in a good way)

Public Domain

Lake Erie and several of its contributing rivers have been the sites of a number of environmental catastrophes. The “death” of the lake was announced in both the media and in the scientific literature back in the late 1960’s, and this pronouncement was punctuated by the fire that spread across the Cuyahoga River in Cleveland in 1969. More recently, green, toxic blooms of algae in the western regions of the lake and up Toledo’s Maumee River has returned the focus of the public to the conditions of the lake.

The Great Lakes are a unique freshwater ecosystem not only because of their size (20% of all of the fresh surface water on Earth is contained in these lakes) but also because of their physical isolation from all of the other freshwater and marine ecosystems of the Earth.  This isolation has allowed the flora and fauna of the Great Lakes to evolve in unique ways, but it has also caused the resulting plants and animals of the lakes to be especially vulnerable to the sudden intrusion of invasive species.

Lake Erie is the shallowest of the five Great Lakes (its average depth is only 62 feet, and its western basin is especially shallow with average depths between 25 and 32 feet). The consequences of Lake Erie’s shallow depth are multifold: 1. It has the smallest volume of the five Great Lakes, 2. It has the shortest “water residence time” of any of the Great Lakes (only 2.6 years), 3. It is the first of the Great Lakes to freeze in the winter, and 4. It is the warmest of the Great Lakes in the summer. The shallowness and warmth of Lake Erie also makes it a particularly ideal habitat for plankton and the diverse food web of fish that rely on plankton for their energy. It is estimated that half of all of the fish in the Great Lakes live in Lake Erie!

Photo by Censusdata, Wikimedia Commons

Lake Erie is also in the center of the midwestern industrial belt and has been used as a transportation and waste removal system for industry and the numerous municipalities that surround it. Approximately, 34 million people live along the shores and in the watershed of the Great Lakes! Lake Erie, because of its small water volume, is particularly vulnerable to industrial and municipal pollution.

Lake Erie (and the other Great Lakes) have been subject to a number of ongoing stresses and cycles ever since Europeans settled upon its shores. Industrial and municipal wastes were relatively unregulated until the early 1970’s, and the lakes steadily built up larger and larger concentrations of sewage, toxic chemicals and metals. Transportation systems allowed first barge traffic and then entire ships to deliver ocean transported cargoes to the ports around the lakes. These systems include the Erie Canal (completed in 1825), the Welland Canal (first opened in 1829 and expanded and lengthened many time afterwards), and the Saint Lawrence Seaway (opened in 1959). These canals and seaways broke down the geographic barriers that isolated (and protected) the Great Lakes and allowed the invasion of exotic and invasive species into rich, but very fragile Great Lakes ecosystem.

Photo by NOAA, Wikimedia Commons

Sea lampreys were one of the first biotic invaders. They swam up the Erie Canal and hitched rides on boats through the Welland Canal. These predatory, jawless fish began to feed on lake trout and, until lamprey control methods were finally developed in the 1960’s, decimated the populations of these commercially important food fish and keystone predators of the Great Lake’s food web. Loss of the lake trout opened the lakes to an explosion of smaller, invasive fish including alewives. The exploding numbers of alewives, then, ate not only an abundance of plankton upon which other native fish species relied but also the eggs and immatures of many native fish species (including perch, lake herring and chubs). Introduction of Pacific salmon into the Great Lakes (particularly Lake Michigan) in the 1960’s was at least partially an attempt to re-establish a large predator in the lakes to control the alewives (which periodically experienced massive die offs because of the stress of life-long, freshwater existence (in their natural, Atlantic coast habitats alewives are anadromous and spend their adult lives in the ocean)). The salmon introduction is often praised as an economic and recreational boon, but this alien species of fish probably insured that the native lake trout would never be able to return to their pre-lamprey numbers and distributions.

Chinook salmon. Photo by USFWS, Public Domain

The Pacific salmon, though, did stimulate recognition of the recreational fishing potential of the Great Lakes, and, in doing so, made the public more aware of the lakes and also of some of the lakes’ problems. As thousands and thousands of salmon were being caught and processed and eaten from the lakes the healthfulness of their flesh came into question. Levels of the pesticide DDT were shown to be very high in the salmon, and later levels of PCB’s, dioxins and mercury. Concerns about health stimulated the public to demand safeguards against pollution, and these concerns were at least part of the impetus for the passage of the Clean Water Act of 1972. With the passage and enforcement of this act, the levels of pollution in the “dead” lakes began to decrease.

Photo by D. Brenner, Michigan Sea Grant. Flickr

More exotic species invaded the lakes: zebra and quagga mussels in some places form a continuous covering across the lake bottoms choking out native bottom dwellers and disrupting delicate food chains. These mussels also build up to such large numbers that water intakes for factories, power plants and water treatment plants have become clogged. Ironically, along with all of this biological and physical disruption the mussels have also, through their constant filtration of the lake waters, improved the clarity and appearance of the lakes, but at a severe cost of their overall productivity.

Photo by NASA, Public Domain

An article in The New York Times (October 3, 2017) described in vivid detail one of the latest rounds of Lake Erie’s environmental problems. A 700 square mile bloom of bright green algae (that includes potentially toxic cyanobacteria) covered the western end of the lake. The green plume, which also extends up the Maumee River at Toledo, was caused by excessive fertilizer runoff from surrounding agricultural lands. The size and duration of these late summer blooms have been increasing since 1985 as has the levels of dissolved phosphorus in the waters of Lake Erie. Ongoing global warming is only expected to make these blooms even more extensive and potentially even more toxic. I talked about the biology of these blooms back in 2014 (see Signs of Summer 1, June 12, 2014). On a small scale these algae blooms are dangerous, on a large scale, as we are now seeing in Lake Erie, they are potentially calamitous.

So Lake Erie is back, but not completely. The algae are clogging its warm, western waters, invasive mussels are altering energy flow, and its fish are still contaminated with PCB’s and mercury. All of the Great Lake states have detailed descriptions of where you can “safely” fish (the least toxic sites) and where you cannot. They have also published descriptions of just how much (or how little) you can safely eat of the fish you catch( see Ohio Sports Fish Consumption Advisory, 2017).  The beauty of lake, though, and it is a spectacularly beautiful lake, can lull you into thinking that there is nothing wrong anymore. We need, though, to use our brains rather than our hearts when we look at these lakes.


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Signs of Fall 12: The Extinction of North American Ash Trees

White ashes on Nature Trail (c. 2000) Photo by D. Sillman

One of my favorite sections of our old, campus nature trail was the first hundred yards, or so, that wound through a volunteer forest of white ash trees. The straight, graceful trunks of the ashes and their deep green, lance-shaped leaves was a wonderful border for the constantly changing forest of the trail. About four years ago, though, I began to see small, D-shaped holes in the bark of these ashes, and about two years ago the trees stopped making leaves. This last winter, storms blew down several of the trees, and the rest are standing dead alongside the trail.

Depending on the relative degree of lumping and splitting of species and subspecies designations, there are between 45 and 65 species of ash trees (genus Fraxinus) around the world. Ashes are found primarily in the northern (temperate) regions of Europe, Asia and North America and range from relatively modest sizes (like the 30 foot tall velvet ash) to trees of substantial heights and girths (like the 120 foot tall white ash). Six ash species are found in North America where they have historically made up a substantial portion of our deciduous forests (it estimated that there are (or were) 8 billion, wild ash trees in North America). Ashes have also been extensively planted in urban and suburban habitats as ornamental trees and along urban and suburban street as shade trees. Ash lumber is used to make everything from furniture to baseball bats, and ash logs are a highly preferred and commercially attractive form of firewood.

Five of North America’s ash tree species, though, have recently been classified as critically endangered. They are teetering on the brink of potential extinction due to the impact of an exotic, invasive beetle from eastern Asia called the emerald ash borer (Agrilus planipennis). Our nature trail ash trees along with most of the ashes in Western Pennsylvania were some of the victims of these rapidly spreading beetles.

Photo by H. Russell, Wikimedia Commons

The emerald ash borer was first observed in 2001 in Detroit, Michigan. Ash trees in Detroit were mysteriously dying, and a small, iridescent green beetle was collected from the logs of the dead trees. The next year across the Detroit River in Windsor, Ontario these beetles were also collected from dead and dying ashes. Within a few years  the emerald ash borer was collected in forests from Minnesota to New York. Within a few years more, the beetle spread north and east across Canada, east and south to the Atlantic Ocean and the Gulf of Mexico, and as far west as Colorado. Currently thirty-one states and two Canadian provinces report the presence of the emerald ash borer. Researchers speculate that the emerald ash borer had been in North America for more than a decade prior to its 2001 “discovery” in Detroit.

The emerald ash borer probably traveled to North America in ash wood used for shipping crates or as packing material in the cargo holds of ships. From wherever it first landed, it then rapidly began its destructive expansion through our deciduous  forests.

Ash borer eggs, Photo by D. MIller, USDA Forest Service

Adult female emerald ash borers mate within a week of their summer-season (June to August) emergence and may fly ten kilometers or more in their search for a suitable ash tree on which they can lay their eggs. Eggs are stuck into the cracks and crevices of the outer bark of the ash and hatch into larvae in about three weeks. The larvae chew their way into the nutrient rich vascular layer (the “phloem”) just beneath the outer bark and begin to tunnel through and feed on this important tissue. Phloem transport sugars and other nutrients throughout the tree, and as it is destroyed, the tree becomes less and less able to sustain itself. After two or more years of feeding and growing the mature

Photo by D. Herms, Ohio State University, Wikimedia Commons

larva fold themselves up into a pupation chamber just beneath the outer bark where they wait out the winter. In April or May they pupate and transform into adults. Adults chew their way out of the pupation chambers (leaving behind their characteristic D-shaped exit holes in the outer bark) in May or June and quickly mate. Each adult female lays on average 55 eggs. Counting the exit holes on a single ash tree suggests that dozens to hundreds of adult ash borers may be emerging each spring from each infected ash tree.

According to entomologists at Ohio State University, 282 species of native arthropods (insects and spiders) rely on ash trees for their food and shelter, and 44 of these species feed exclusively on ash trees. Other Ohio State scientists have observed that in forests affected by emerald ash borers there are almost no ash seeds in the soil seed bed, and that after the death of the standing ashes, there are no ash seedlings germinating to replace them.  The sun gaps that form from the deaths of the ashes typically are filled up with fast growing, exotic invasive plants like oriental bittersweet, honeysuckle and multiflora rose which shade out and choke out native under-story plants and most of the potential tree seedlings. A dense, shrubby patchwork of invasive plants, then, replaces the destroyed ash forest.

Two dead ash trees, Photo by M. Hunter, Wikimedia Commons

The ash trees of East Asia have evolved mechanisms to control the emerald ash borer. Native, healthy ashes (like the Manchurian ash) are avoided by the adult female ash borer because of the ability of these healthy trees to make inducible, protective chemicals that can kill the borer’s larvae. Emerald ash borers instead seek out sickened, native trees or non-native species of ash that are not able to synthesize these protective chemicals. Some experiments here in North America have involved spraying specific plant alarm chemicals and hormones (like methyl jasmonate) on infected ash trees. Results of these experiments have suggested that these natural plant compounds may help the trees to fight off the emerald ash borer beetles as effectively as insecticides.

The emerald ash borer has been called the “most destructive and economically costly insect ever to invade North America.” It is ravaging the ash components of our wild forests and destroying the graceful ash trees of our cities and neighborhoods. Monitoring programs and attempts at quarantine and control have been ineffective in stopping or even slowing down this pestilence. Many forest scientists have already given up on trying to save these trees. Their extinction will occur, possibly, in the next few years! I mourn the loss of the white ashes of our nature trail and all of the billions of less seen ashes along our ridges and in our valleys.



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Signs of Fall 11: Lyme Disease and Vaccines

Photo by D. Sillman

In June 2017 I wrote my annual blog about black-legged ticks and Lyme disease. I won’t talk about the tick life cycle again until next spring, but I do have some updates and new perspectives about the disease and also about the ticks that transmit it.

First of all, Pennsylvania is once again leading the nation in cases of human Lyme disease. The final numbers are not yet in for 2017, but the Center for Disease Control (CDC) recorded 12,092 reported cases of human Lyme disease in Pennsylvania for 2016, and these data maintained the five year pattern of 25 to 33% yearly increases in human cases of Lyme in the state. A recent publication by the CDC further noted that the reported cases of Lyme probably represent only 10% of the actual cases. They calculate that there are over 300,000 cases of human Lyme disease in the United States each year and about a third of these cases are in Pennsylvania! Lyme is now the fastest growing, vector-transmitted disease in the United States!

I mentioned in my June 2016 post that the spirochete bacterium that causes Lyme disease (Borrelia burgdoferi) also infects dogs and can cause debilitating (limb paralysis) and occasionally fatal (kidney failure) reactions. The good news for dogs is that there is a vaccine that effectively generates immunological protection against B. burgdoferi infections and also reduces the severity of the Lyme syndrome if an infection does get established. The very puzzling part of any discussion about this dog vaccine, though, is the realization that there is not a human, anti-Lyme vaccine currently available to help control this growing epidemic of human Lyme disease.  A CDC discussion site actually reported cases of desperate people convincing their veterinarians to give them injections of the dog anti-Lyme vaccine!

This vaccine discussion begin to get even more absurd when you realize that there exists not just one but two human anti-Lyme vaccines! One of these was actually available to the public about twenty years ago and the other one passed through clinical trials but was never released for general distribution. What happened to these vaccines, and why can we not use them?

The answer to that question lies in outside the realm of science. A consideration of the history of vaccines may help us understand our current dilemma.

Edward Jenner by James Northcote, National Portrait Gallery, Wikimedia Commons

Most medical historians start their discussion of vaccines in the last decade of the Eighteenth Century with Edward Jenner and his cow pox inoculations. Jenner noticed that milk maids, who were exposed to the relatively mild virus that causes cox pox, were then immune to the extremely serious and frequently lethal virus that causes small pox. Small pox had been a scourge of humanity since the invention of agriculture (10,000 + years!), and it is thought to have been an animal virus that escaped into human populations from either cattle or camels. In Eighteenth Century Europe 400,000 people died every year from small pox!

Jenner’s observation was an incredibly insightful one, but the idea of vaccination (even though Jenner was the first one to coin the term) had existed for a much longer period of time. Healthy individuals possibly for centuries in India and China had undergone a process called “variolation” to protect them from small pox. Variolation involved removal of some of the puss from a fresh small pox lesion and its transfer, subcutaneously, to a healthy individual. The inoculated individual, then, typically, experienced a mild immune reaction (fever, aches, etc.) but developed an immunity to the small pox virus. The transfer of fresh fluids from a small pox patient, though, could also sometimes transfer the actual virus causing the recipient of the inoculation to actually develop small pox. It was, then, a fairly dangerous procedure. In spite of that, variolation was widely practiced across Europe throughout the Eighteenth Century and many stories of aristocratic families inoculating their offspring added greatly to the acceptance of and desire to undergo the procedure.

In 1796, Edward Jenner utilized puss from a pustule on a cow (whose name, by the way, was “Blossom”) to inoculate a young boy. The boy experienced a period of fever and immune reaction symptoms but was, then, immune to small pox. The weaker, cow pox virus “tricked” the human immune system to make the immunological proteins and cells that could destroy the small pox virus. It was a great victory for both medicine and science and subsequently saved countless numbers of human lives, but not everyone was pleased with the idea of vaccination!

Jenner among his patients. Wellcome Images, Wikimedia Commons

Satirical cartoons from early Nineteenth Century publications show people developing legs and heads of cows after receiving Jenner’s inoculation. The cross-species nature of the inoculant, and the “un-natural” process of the inoculum transfer, caused many groups to forcefully resist receiving the vaccine. People rioted, attacked the inoculators and were arrested and jailed as a consequence. Jenner, although eventually lauded by many in his professional and social spheres, was the object of widespread ridicule and the recipient of constant death threats. Something deep and primal had been awakened in the superstitious minds of people, and they focused on vaccination as a fundamental invasion of their bodies by forces of government and science.

Sadly to say, this superstitious reaction to vaccination has not gone away. Small pox, as we should all be grateful, is extinct and the virus now only exists in two extremely secure medical repositories. Almost every other vaccine since, though, has had to face the loud and emotional (and often incredibly ignorant) criticism of the anti-vaccinators. Here is a link to very readable history of the anti-vaccine movements that was published by the College of Physicians in Philadelphia.

Anyway, this was the buzz saw that the human anti-Lyme vaccine ran into. A small group of people claimed that the vaccine caused paralysis (no clinical evidence supported this). This group threatened legal action against the pharmaceutical company that had released the vaccine and also mounted an extremely effective public relations campaign against the vaccine. Under the weight of these attacks and under threat of skyrocketing legal costs, the company stopped manufacturing the vaccine, and the second company decided never to release their vaccine. In the 1990’s when the vaccine was initially released the number of Lyme cases in the United States were much lower than today, so there was little economic incentive for the pharmaceutical company to continue to make the vaccine. Possibly, as the number of Lyme cases per year increase, someone might be brave enough to re-release one of the vaccines.

Photo by K. Laubenstein, USFWS, Public Domain

One last thing about black legged ticks, B. burgdoferi, and the mice that are the lynchpins in their infectious cycles: in a study published this summer in the Proceedings of the Royal Society B the presence of active mice predators (foxes, martens, weasels etc.) did not significantly reduce local populations of mice. The presence of these predators, though, did reduce the number of ticks each mouse had on them (a 90 to 95% reduction!) and also reduced the number of ticks that were carrying the B. burgdoferi bacteria (a 96% reduction!). Speculating on these findings, the study’s lead researcher, Dr. Tim Hofmeester, felt that the presence of the predators curtailed the movements of the mice and acted to disrupt the proliferation and spread of the ticks and, possibly, their intra-specific exchanges of the bacteria!

Stop Lyme disease by adding foxes and weasels (and how about coyotes?) to our fields and woods and neighborhoods? Works for me!


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Signs of Fall 10: Shoulder Seasons, Elk and Goats

Photo by D. Sillman

I was reading a paper a few days ago about some of the potential impacts of a warming climate on the hardwood forests of eastern North America when I came to the following sentences:

“…. you have to look at things like competition. Young trees rely heavily on the shoulder seasons — spring and fall — to grab the light they need.”

Shoulder seasons? New terms are always popping up, but they usually have some obvious roots or contexts. Who calls the spring and fall the “shoulder seasons?” I took to Google to find out!

The travel and tourism industry, apparently, regularly uses this phase to identify the times in between the peaks and the lulls of travel. If you imagine an X-Y graph with a Y-axis representing hotel reservations made at some seaside resort or plane tickets bought to travel there, and an X-axis that represents the months of the year, you could visualize large numbers of visits and flights in the summer and some very low values in the winter. Connecting these peaks and lulls is the sloping rise or fall that represented the transitional seasons. Slopes that could be called the “shoulders” of the graph!

Backpacking uses the term “shoulder season” for the early spring and late fall, times when winter is lingering or coming on sometimes astonishingly quickly. The shoulder season is a good time to find open trails and empty camps (and maybe a foot of snow on your tent when you wake up in the morning!).

The term is also used by people who burn wood for heat or cut logs for firewood. It has been also been used to describe the timing of particular hunting seasons (like the ‘elk shoulder seasons” in Montana). Gardeners use the term to talk about squeezing in a quick crop of beans or squash before winter slams the door on plant growth. A Lutheran minister talks about the “shoulder times” just before Christmas as the ideal time for true religious contemplation. There are also all sorts of clothes and fashion accessories all focused on this very interesting time (and term!).

I don’t what I would have thought if I had come across Montana’s “elk shoulder season” before I had explored this word. I think I would have envisioned images of gruesome carnage in the mountains with shoulderless elk carcasses strewn across the countryside and discrete racks of elk meat grilling over camp fires.

Photo by Rachel J., Pixabay

Speaking of elk: there was a paper published this past summer (PLOS ONE, June 14, 2017) that explored the survival behaviors of a herd of elk in southwestern Canada. Human hunters are the primary predators of these elk, and because of hunting regulations and trophy considerations the male elk (“bulls”) are the herd component that is preferentially hunted and killed. Males are also easier to hunt because they can be actually drawn to hunters because they respond so predictably to the mimicked bugling calls of potential competitors. It is not surprising, then, that bulls of this herd typically only live to five years of age.

Female elk (“cows”) are also hunted although somewhat less intensely. Cows can live up to twenty years and hunting censuses have noted that cows older than ten years of age are almost never taken by hunters! Researchers at the University of Alberta wanted to explore the reasons for this remarkable survival rate of these older cows. Did they survive because they simply had been born very careful and cautious and remained so all of their lives (a “nature” explanation)? Or had they developed increasingly effective survival skills through their long lives through learned interactions with potential hunting experiences (a “nurture” explanation)?

Photo by T. Hisgett, Wikimedia Commons

The researchers, intensively monitoring the movement of forty-nine cows over periods of two to five years with GPS collars, found that both explanations were appropriate. Cows begin life with a higher level of caution than bulls and are thus genetically able to more effectively avoid hunters (and, logically, other potential predators, too). This innate level of caution, though, becomes more developed as the cow ages. Older cows move shorter and shorter distances during the day, and they seek rougher, more remote terrain, and actively avoid roads and other human impacted landscape features. Any experience involving human hunter contact quickly leads to a particular cow avoiding that terrain or locale in the future. Cows also tend to live in small groups and are able to share their hunting avoidance experiences and thus expand the entire group’s overall survival strategies.

So, these elk cows because of innate caution and a high level and quality of learned (and shared) experiences, become almost invulnerable to hunters. They are able to live and reproduce well into their second decades of existence.

Photo by F. Dunn, Flickr

And finally, in Morocco a historically hot and dry climate that has become even hotter and drier under the influence of ongoing climate change. Moroccan goats, a very abundant domesticated animal that has for millennia scrambled agilely over the rocky hillsides to glean and gather plant materials for their food, now face many months of the year where there are no food materials to be found among the rocks. These goats in response to this food deprivational stress have developed new behaviors that enable them to survive in their changed world. They have learned to climb the scattered argan trees! Up in the branches of these trees the goats graze on both leaves and the nut-like seeds. The human, goatherds actually prune the lower tree branches to help the goats make the leap from the ground into the trees! In the autumn, the height of the dry season in Morocco, few goats are seen on the rocky hillsides! Instead, in scenes that evoke illustrations from Dr. Seuss, the goats are all up in the trees!

As Michael Creighton wrote in his novel Jurassic Park, life will find a way!

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Signs of Fall 9: Tree of Heaven

Photo by D. Sillman

In Betty Smith’s novel, “A Tree Grows in Brooklyn,” the sight of a Tree of Heaven pushing its way up through the endless concrete and brick of the Williamsburg tenements is an inspiring metaphor for the robustness and tenacity of life. If a tree can survive all of the vicissitudes of that harsh, urban existence, then so can the protagonists of the novel, and, maybe, so can we all. This is a wonderful book, but I wish that Smith had used a different tree for her focus: maybe a red maple, or a honey locust or a London plane tree. Choosing a Tree of Heaven ennobles an invasive species that is inflicting great damage on our native forests!

Tree of Heaven (Alianthus altissima) has  number of apt, but less exultant names: “stinking sumac” or more simply “stink tree” emphasize the abundant, odiferous chemicals that it emits from its roots, leaves and bark. “Ghetto palm” or “tree of hell” emphasizes its ability to thrive in polluted, stressful environments. Tree of Heaven is native to northern and central China and Taiwan, and the Chinese name for this tree (“Chochun”) translates to into “foul smelling tree.” The name Tree of Heaven was coined because of the species’ very fast vertical growth rates (it “quickly reaches for the heavens!”). Initially, it was touted as a rapidly growing shade tree that could add great quality to a garden or street-side tree lawn.

Tree of Heaven was first introduced to North America in 1784 by a Philadelphia gardener and landscaper named William Hamilton (no relation!) who advocated its planting as a shade and ornamental tree. A second wave of Tree of Heaven introduction occurred in 1820 in Flushing, Long Island.  A large, local tree nursery promoted the species emphasizing its exotic nature and its rapid growth rate. A third introduction occurred in California as Chinese immigrants brought Tree of Heaven with them as both a reminder of their homeland and also as source of traditional, medicinal chemicals. Very quickly, though, the invasive and destructive properties of this species were recognized and active planting and propagation were discontinued.

Free use photo, Pixabay

Once established in an area, Tree of Heaven will both persist and spread. A paper published by Penn State researchers this past August in the journal Forests detailed some aspects of the species’ reproductive potential. A female Tree of Heaven can make up to 325, 000 winged seeds in a single season, and these trees begin to make seeds at a very young age. By age 40 a female Tree of Heaven will have made 10 million seeds! By age 100 (and thankfully most Tree of Heaven don’t live that long) a female Tree of Heaven will have made 52 million seeds! The good news is that these seeds do not persist very long in their seed beds (they are viable for only a year or two), the bad news is that their winged samara can carry them great distances, and they have a very high rate of germination. The seeds from 40 year old trees had 78% germination rates while seeds from 100 year old trees had 66% germination rates. The researchers compared this to the seeds of tulip poplars which have a germination rate of only 9%! Many of the dispersed Tree of Heaven seeds, then, will generate new seedlings!

The Tree of Heaven grows most rapidly in full sun (a vertical growth rate of 3 to 6 feet per year in each of the tree’s first four years of life is typical), but it is able to tolerate shady, forest floor conditions. These are trees, then, that especially fill in the sun gaps and the edges of a forest. Environmental factors that cause the deaths of mature trees (like gypsy moth outbreaks killing oaks, ash borers killing ash trees, and wooly adelgids killing hemlocks, etc.) will accelerate the invasion of Tree of Heaven. Disturbance to an established forest will also facilitate Tree of Heaven invasion. The tree’s ability to grow even in very harsh conditions or in nutrient-poor soils also potentiates its invasive dispersal.

Photo by D. Sillman

Tree of Heaven is also able to propagate itself vegetatively via sprouting from root suckers. An established tree can send up new shoots up to 50 feet away and is, thus, able to quickly fill in a very wide area. Tree of Heaven also produces allelopathic chemicals that powerfully inhibit the growth of potential competitors. An established tree and its clones or offspring alter the fundamental flora in their understory and inhibit the growth of longer-lived, shade producing trees that might allow a forest succession sequence that could exclude it.

Finally, Tree of Heaven is not readily eaten by white-tailed deer. The abundance of noxious chemicals that it synthesizes makes its leaves and shoots unpalatable to most herbivores. Deer, as we have talked about many times before, are a major sculpting force in our developing Eastern forests. By consuming tree seedlings other than Tree of Heaven, the white-tailed deer are opening more and more of our forests to the establishment and perpetuation of this invasive tree.

It is very difficult to get rid of Tree of Heaven! Cutting mature trees leads to stump and root sprouts. Spraying trees with herbicide stimulates vigorous root sprouting. Regular mowing of areas with sprouts and seedlings is an effective way to extirpate the species, but this is not always possible in forested habitats. Planting other, fast-growing trees to generate a shady environment can be a good, long-term plan to eliminate Tree of Heaven, but any edges or sun gaps or spaces in between the shade trees will undoubtedly fill in with the extremely fast growing alien invader.




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Signs of Fall 8: Wood Frogs and Climate Change

Photo by D. Sillman

There is a population of wood frogs (Rana sylvatica) down at Ohiopyle, Pennsylvania that Deborah and I and Rob and Michele Bridges look in on during our annual, early March hike around the Ferncliff Peninsula. Most years there are only a few frogs quacking in the scattered vernal pools, although one year (2013) we hit the jackpot and timed our hike with the frogs’ mass emergence from hibernation into an abundance of water-filled pools. The past two winters, though, have been mild with very little snow, so the vernal, frog-breeding pools did not fill up or persist very long into the spring.

Wood frogs are found from northern Georgia all the way up to the Arctic Circle. It is, in fact, the only “cold blooded” vertebrate that lives north of the Arctic Circle! They utilize temporary pools formed by spring rains and snow melt as breeding ponds and then spend most of the rest of their active season away from standing water. Adult wood frogs feed opportunistically and extensively on small insects and other invertebrates. They use their long, sticky tongues to capture prey and are said to eat “anything that they can fit into their mouths.”

The ability of wood frogs to survive in high latitude ecosystems depends upon a number of specialized physiological adaptations that enable them to tolerate being almost completely frozen through the long winters. There is a cost to this extreme hibernation, though. The longer the frog is frozen, the more likely it is not to survive.

As soon as the wood frog thaws in the spring, it moves to its breeding pools which are free of fish and other potential egg and tadpole predators. These pools, though, are inherently transient and dependent upon unpredictable weather conditions. The use of these temporary pools, then, represents a very delicate, ecological “cost-benefit” balance for the species.

Photo by D. Sillman

In the mating pools, males call to females with their “duck-like” songs. An attracted female enters the pool and is quickly grasped on the back by the smaller male (this is called “amplexus”). The male may remain in place on the female’s back for 24 to 72 hours and will release his sperm into the pool water as the female ovulates and thus externally fertilizes the forming egg mass. A typical egg mass contains 1000 to 2000 eggs. The female moves the floating egg mass into the shallow areas of the pool in a large, communal raft. Counting these rafts in an area’s pools is an accepted, and highly efficient, way to determine the population density of the wood frog in a particular region.

Since mating and egg laying occur very soon after ice melt, the chance of seasonal, sub-zero temperatures re-occurring is quite high. The eggs and embryos of R. sylvatica have an interesting adaptation that enable them to survive both transient and sustained periods of freezing and sub-freezing temperatures. The melting point (i.e. temperature at which material changes from a solid (frozen) to liquid state) of the mucopolysaccharide and mucoprotein “jelly” that surrounds the eggs and the developing embryos is higher than that of the fluids inside the egg. As temperatures fall, then, the jelly freezes before the egg or embryo. This freezing osmotically draws water out of the egg into the jelly mass. The dehydrated egg and embryo, then, are more resistant to freeze damage and are thus able to better survive the early spring temperature fluctuations. Larger embryos in particular, are more tolerant of longer periods of freezing, so severe weather patterns may generate a selection pressure for faster growing, and, thus, larger and more resistant embryos.

Wood frogs are important models of some of the potential effects of climate change. Warming temperatures could, logically, reduce the hibernation stress on wood frogs but may also push the frogs past their upper limit of temperature tolerance during their spring and summer activity periods.  Also, changes in precipitation patterns, especially changes in snowfall and in spring rains, could have large effects on the size, availability and persistence of the vernal pools that are critical for the reproduction of this species.

Photo by D. Sillman

A consortium made up of the U. S. Geological Survey and fourteen universities (including Penn State) looked at the sizes and reproductive health of 746 populations of wood frogs scattered across North America from Tennessee up into Canada to try to determine what the effects of climate change might be upon this important, bell weather species. Their results were published in the August 19, 2017 e-journal, Global Change Biology.

Warming temperatures had a negative effect on wood frogs in the southern (warmer) areas of their range, but increased temperatures had a positive (stimulatory) effect on wood frog populations in the middle and more northern areas. Increased precipitation, though, even in areas that were normally moist, was found to consistently benefit wood frogs numbers and reproduction (as measured by egg counts) especially when this increased rainfall was coupled to increased temperatures.

This study, then, noted that the North American distribution of wood frogs is likely to shift northward as the result of climate change, but somewhat surprisingly also found that the impacts of warmer temperatures and increased rainfall in the middle and more northern regions of the species’ range were likely to have positive effects on the species’ numbers and reproductive rates.

So ongoing climate change is having a complex impact on wood frogs. Some populations of wood frogs in certain locations will be benefited by climate change while other populations in other locations will be negatively impacted. This is likely to be the model of response that we will see in other species whose physical environments are being altered by changes in seasonal temperature and precipitation patterns. The influences of the interactions of a species with other members of its unique biotic community, the influences of specific features of a species’ physical environment, and the potentials for local adaptations to the changing climate matrix will all combine to make each population’s response to climate change unique.






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Signs of Fall 7: Hurricanes

Hurricane Irma, NASA

This year’s Atlantic Basin hurricane season has already surpassed all predictions in both the number and intensity of storms, and we have, at this writing, six weeks left in the season for more storms to arise! There have been (as of October 19) fifteen named storms and ten hurricanes. Five of these hurricanes have been “major” (Category 3 or above) (Harvey (a 4), Irma (5), Jose (4), Lee (3) and Maria (5)). Three of these five major storms had extensive contact with land masses and have done considerable damage to both human habitations and natural ecosystems. An index that measures the number, the strength and also the duration of a season’s storms is called the “Accumulated Cyclone Energy” (ACE) Index. Based on this index, 2017 is already the eighth most intense hurricane season of all time!

Many animals were affected by Harvey, Irma and Maria. Cows, horses, chickens, goats, dogs and cats all suffered grievously from the effects of these storms and relied on their humans to help them survive. Zoo animals had to be sheltered in place or removed to safer, inland sites. Dolphins in Cuba were removed from their dolphinarium on Cayo Guillermo and helicoptered away from the path of Irma. The Humane Society has set up a special fund to help domesticated animals that have been displaced by these storms.

Wild animals also were affected by these hurricanes. Some large, strong flying birds were able to fly out ahead of the storms, but most species had to shelter in place and ride out the wind, rain, and flooding.

Hurricane Harvey was a slow moving, monster of a storm. After it hit the Texas Gulf coast, it inched its way along dumping a year’s worth of rain on some areas around Houston. The flooding was incredible and the effects will be felt for many years. On a beach near Texas City, Texas the storm pushed a seldom seen sea creature onto the sand. The three foot, toothed serpent was a fangtooth sea eel (Aplatophis chauliodus) a bottom dwelling predator that is normally found burrowed in the sediment at depths of 100 to 300 feet. The energy of the storm must have dislodged it and flung it up on to the shore. I could not find a free use photo of the sea eel and so include this LINK to an article (with pictures!) about it.

Harvey also forced many shore birds far inland. Sooty terns, magnificent frigate birds, royal terms, Caspian terns, least terns and Sabine’s gulls were pushed up to 200 miles into the Texas Hill Country. Many showed up around the lakes near Austin giving central Texas bird watchers a great chance to expand their life lists!

Photo by USFWS, Public Domain

West of Houston is the Atwater Prairie Chicken Refuge. The wild population of these endangered birds only numbered 42 individuals before the storm. After Harvey only 5 hens survived. The refuge also houses a population of bob-white quail that were decimated by the torrential rains and flooding. In nearby coastal refuges thousands of dead birds were reported (especially pelicans, terns and gulls). Song birds were also assumed to have been killed in large numbers, although their small carcasses were very difficult to observe or recover.      

The Aransas National Wildlife Refuge is just north of Rockport, Texas (the site of Harvey’s first landfall). It is a large, vital over-wintering reserve for a number of migratory bird species including the endangered whooping crane. Harvey pushed tons of saltwater into the refuge’s freshwater ponds and piled up massive quantities of man-made materials all over the refuge. Fortunately, the whooping cranes had not yet arrived when Harvey hit although their over-wintering habitat is severely damaged.

Raft of fire ants. Photo by The Coz, Wikipedia Commons

An animal that seems to have thrived in the post-hurricane floods in Texas was the exotic, invasive, and extremely destructive, fire ant. Reports described floating masses of fire ants held together by their intertwined legs, bobbing along in the flood waters around Houston. These masses dispersed when they reached dry land and inflicted their severe stings on anyone who came in contact with them.

Hurricane Irma was a fast moving, powerful wind and rain storm. It generated 185 mph winds and tore across several Caribbean islands, the Florida Keys, and up the entire state of Florida. Strong flying, tropical birds, as we saw in Harvey, were scattered out ahead of the storm and were seen as far north as Kentucky. Upland habitats of southeastern Florida and the Keys were defoliated by the wind. There will be, then, no food or shelter for the flocks of migrant species that will be following the Atlantic Flyway this fall and winter. The Everglade snail kite (an endangered raptor) had all 44 of its nests around Lake Okeechobee destroyed by Irma.  On the island of Barbuda, amazingly, many of the near-threatened Barbuda warblers survived the destruction of their dry shrubland habitat. Magnificent frigate birds, though, that nest in large numbers on Barbuda were decimated by the storm. The endangered Key deer were able to find shelter and high ground as Irma struck and were reported on Big Pine Key a few days after the storm.

Loggerhead sea turtle, Photo by Strobilomyces, Wikimedia Commons

Sea turtles were severely impacted by Irma. Hundreds of young, endangered loggerhead and green turtles were pushed onto shore by the storm where they were rescued by human volunteers. Nests, though, were washed away by the extensive beach and dune erosion of Irma. On beaches south of Cape Canaveral 90% of the loggerhead turtle nests were destroyed.  Green sea turtles were nesting in record numbers all along the Florida coast, and huge numbers of these nests were also lost.

One Florida Fish and Wildlife Commission spokesman talked about bears and racoons actually thriving in  post-impact ecosystems of Irma. Increased shelter (downed trees) and food (carcasses and scattered human food debris) will actually benefit these two hardy and omnivorous species.

Photo by USFWS, Public Domain

Hurricane Maria was also a fast moving wind and storm event. Winds in Maria reached 160 mph, and it hit the island of Puerto Rico head-on.  One site that is representative of the extensive destruction all across the island is the El Yunque Rain Forest. El Yunque is the only rain forest in the U. S. Forest System. It is the site of rare and unique trees, and numerous and endangered birds and amphibians. The entire rain forest was shredded by the winds of Maria destroying the forest’s ability to shelter and feed its numerous animal species. One inhabitant of El Yunque is the endangered Puerto Rican parrot. In 1989 after Hurricane Hugo there were only 22 of these parrots left. Careful conservation of these survivors and established breeding programs (both captive and wild) have brought the numbers of these parrots up to 500 individuals. Many wild parrots died due to Maria, but it is hoped that there are sufficient captive birds to re-establish a viable population.

Ecologists stress that forests like El Yunque in Puerto Rico and animals like the Puerto Rican parrot and the sea turtles we have discussed have evolved in environments where hurricanes regularly occur. The long-term impact of these hurricanes, as long as they do not ravage a site too frequently, may, in fact, be beneficial to the overall health and vigor of these ecosystems and species.   Climate change models, though, predict both increased intensity and increased frequency of these major hurricanes. The increased frequency, in particular, could be devastating to all of these sites and organisms.


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Signs of Fall 6: More on Yellowstone

Photo by L. Drake

On our drives and hikes through Yellowstone National Park we saw (as I mentioned last week) two wolves (pictured at a distance to the left), one bald eagle, a dozen sandhill cranes, a hundred elk, and a couple of hundred bison. The most abundant large organism we saw, though, numbered in the millions. We drove past and hiked through vast mountainsides covered with lodgepole pines. These pines were noteworthy not only for their incredible abundance but also for their remarkable uniformity. It was like someone had used CGI technology to replicate a tall, thin, astonishingly straight, incredibly uniform looking pine tree thousands and thousands of times over. These vast tree armies reminded me of the orc or elf or dwarf armies in the various Lord of the Rings movies. They were the most natural looking, unnaturally repetitive set of trees I think that I ever seen!

Photo by B. Olsen, Flickr

The lodgepole pine (Pinus contorta) is found broadly across western North America from the Pacific Ocean’s coast to the northern parts of the Rocky Mountains. There are four subspecies of P. contorta: the “beach pine” (P.c.bolanderi) of northern California, the “shore pine” (P.c.contorta) of northern California up into Alaska, the “tamarack pine” (or “Sierra lodgepole pine”) (P.c. murrayana) of the mountains of southern California and Nevada up the Sierra Nevada into the Cascades), and the “Rocky Mountain lodgepole pine” (P.c.latifolia) which we saw so abundantly in Yellowstone.

Many of the shore species grow in forms that fit the “contorta” species name: they are short, twisted, stunted, shrub-like trees. The Sierra lodgepole pine and the Rocky Mountain lodgepole pine, though, can reach substantial heights (130 to 160 feet) and girths (over six and a half feet dbh). The species designation “contorta,” though, is said to be based on the characteristically twisted needles seen on all of the sub-species. Lodgepole pines can live for up to 400 years if conditions are stable.

Photo by D. Sillman

Fire is an important environmental factor especially for the Rocky Mountain lodgepole pine. The mature tree is actually quite susceptible to fire-kill because of its thin bark, but its seed bearing cones are designed to only open after they have been heated to 113 to 140 degrees F. The lodgepole pines begin to make cones when they are six or ten years of age, and these cones (and their seeds) can accumulate for many decades on the forest floor. So when a lodgepole pine forest burns (which historically happens every  100 to 300 years) a new forest of pine seedlings quickly springs into existence. This is why lodgepole pine forests are typically so evenly aged (and so remarkably uniform in appearance!). The succession sequence in these fire driven forests, then, is short, rapid and focused on the tree species that is best adapted to the high altitude, short growing seasons, and relatively dry conditions of these sites: the lodgepole pine.

Native Americans of the Great Plains traveled great distances to the Rocky Mountains to gather lodgepole pine logs for their tipis. A typical tipi would use more than a dozen, 15 to 18 foot pine poles to support its buffalo skin encasement. The narrow diameter and straight growth aspect of these poles and the low density (and light weight) of the wood made them ideal structural supports for the frequently moved tipis.

Photo by D. Sillman

One of our hikes in Yellowstone was around Ice Lake in the northwestern section of the park. Ice Lake was the site of a severe forest fire in 1988 that destroyed its mature lodgepole pine forest. The logs from this burned forest still litter the surrounding landscape, and lay sun-bleached and slowly decomposing on the dry forest floor. A number of the logs have been actively split (by bears, perhaps, seeking grubs?) and their torn and shredded woody materials have been mixed in with the slowly accumulating needles from the new pines. After 28 years of growth the new pines are about 20 feet tall and 4 or 5 inches in chest high diameter. There were also a few standing,

Photo by D. Sillman

older trees that somehow survived the 1988 fire. Pine cones were seen on the older trees and also on many of the young, re-growth trees. They were also seen in the growing mass of dry material that was accumulating on top of the sandy soil. Although a few understory plants were observed (especially “fireweed” (pictured to the left)) in the incompletely shaded forest floor, most of the plant growth in this forest were lodgepole pine seedlings, saplings and pole trees. The scattered herbaceous plants provide food for grazers (like elk and deer), but they will soon be shaded out by the coalescing pine canopy.

Photo by D. Sillman

A similar burn area in between Yellowstone and the Grand Tetons was described in a recent New York Times article (September 13, 2017). This lodgepole pine forest burned seventeen years ago (in 2000). The pre-fire forest was 200 years old and, so, had a substantial cone and seed reserve. The post-fire response was robust with 32,000 lodgepole pine seedlings per hectare densely filling the burned area. This recovery forest, though, did not have its ecologically expected 100 to 300 years to grow and accumulate new cones and seeds. Instead, because of ongoing climate change and the associated elevated temperatures and reduced moisture (especially reduced snowfall) a part of this young forest re-burned in 2016. Because of the very short time interval between forest fires, this forest had a very small cone and seed reserve and re-generated a very sparsely treed pine forest (only 400 lodgepole pine seedlings per hectare (1.25% of the original post-fire forest)). These scattered pine trees will never completely shade their forest floor and, so, will be under intense competition from aspens and a wide variety of herbs and grasses. It is possible that this more sparsely treed forest will not be sustainable or stable. It is, in fact, possible that these more frequent burnings could lead to the extinction of the lodgepole pine!

Lodgepole pines make up 80% of the trees in Yellowstone National Park. The transition of this pine forest into one dominated by aspens or some other deciduous species would radically change the ecological dynamics of the entire Greater Yellowstone Ecosystem.  Every organism from marmots and elk to grizzly bears would be affected. We’ll just have to wait and see if the pine forests find some new way to survive.




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Signs of Fall 5: Yellowstone

Photo by L. Kalbers

I had the great pleasure of visiting Yellowstone National Park this past August as part of my daughter’s “wedding week.” My immediate, and wonderfully expanding family (Deborah and I, Marian and Lee, and Joe and Marlee) met up in Gardiner, Montana and did some day hikes in the park. We then took a long, touristy drive down through the park, past the Tetons and through Jackson Hole on our way to Victor, Idaho for the wedding. It was a wonderful week (and a wonderful wedding, too, by the way!).

I have been trying to write about Yellowstone ever since but have had trouble narrowing down my focus to some describable aspects of the place. I wanted enough detail so that I could be ecologically accurate on whatever subject I settled on, but I also wanted to connect the pieces of all of the geology and ecology that surrounded us. Yellowstone is not an easily narrowed space or topic!

When you drive into the park you feel that something has changed around you. There is something unusual about the shapes of the surrounding mountains and the dimensions of the valleys that they surround. Yellowstone is not Montana or Wyoming, it is a world unto itself. It looks different and it feels different, too. As my new son-in-law, Lee, pointed out, many of the mountains we were driving past and hiking through were actually rims of ancient, volcanic calderas, and many of the rock formations we were looking at were, in fact, relics of the eruptions that created these calderas. The size and scope of Yellowstone Lake in the center of the park is also startling: this is a region of mountains, dry grasslands and fast rushing rivers! Where did this huge mass of still water come from, and why is it bubbling around its edges?

Public Domain, Wikimedia Commons

So even without “book knowledge” of the fifty mile wide mantle plume of hot magma that rises up under the park, or a visualization of the melted ball of crust that the magma is generating and sustaining just three miles beneath the Earth’s surface, you can see that Yellowstone is topographically different from almost any other place on Earth. When you then add the geysers and mud pots and hot springs and the rainbow array of colors that all of the dissolved minerals and all of the ancient, thermophilic bacteria generate (2/3 of the world’s geysers and half of all of the world’s geothermal features are found in Yellowstone!) you know, to quote Dorothy from the Wizard of Oz, that this “isn’t Kansas anymore!”

National Park Service

The Yellowstone system has had three, “supervolcano” eruptions over the years: 2.1 million years ago, 1.3 million years ago, and 630,000 years ago. These eruptions deposited thick blankets of ash many hundreds of miles away, caused extensive species’ deaths and maybe even  extinctions and probably altered the climate of the entire Earth. Each eruption was thousands of times larger than the 1980 eruption of Mt. St. Helens, and they left behind the distinctive topography of present day park.  The North America tectonic plate, on which Yellowstone sits, is moving toward the southwest at a rate of about one half an inch a year. The plate, then, is slowly dragging itself across the stationary mantle plume and has generated a whole series of “ancient Yellowstones” off to the south and west of the park’s present day location.

USGS, Wikimedia Commons

The volcanic history of Yellowstone can also be tactilely experienced! On one of our hikes in the north-central part of the park, there were large boulders and scattered pieces of obsidian (volcanic glass). We picked up some of the smaller pieces and could feel their incredibly smooth textures and could rub our thumbs across their sharp edges.  Lee showed us on several medium-sized pieces etchings made by Native Americans hundreds of years before as they flaked off sharp arrow and spear points. These obsidian deposits were an important resource for weapons and tools of these hunter-gatherer peoples.

Obsidian can also be used to make surgical scalpels that have cutting edges that are sharper and more smoothly configured that even the finest metal blades. Cutting edges of only three nanometers are possible in these obsidian scalpels. Research has shown that surgical incisions with an obsidian blade generates less of an inflammatory response and initial scar tissue formation than the finest, metal scalpel. Possibly, someone will return to these obsidian cliffs to gather and flake these unique volcanic rocks to make the surgical tools of the future.

Photo by L. Drake

We saw so much in Yellowstone! Elk and bison, mule deer and bald eagles, moose (some of us saw moose, anyway, not everybody was that lucky), big-horned sheep, grizzly bears and wolves! Our wolves were out in a big, wet field about a quarter of a mile off of the roadway. They attracted a large, roadside crowd but seemed unconcerned by the growing audience or all of the attention and clamor. The two wolves played in ways familiar to anyone who has dogs: forelegs down, hind quarters up, circling, lunging and sparring with each other, tongues lolling out of their mouths, joy on their faces.

Photo by D. Sillman

The whole roadside traffic jam phenomena was amazing to experience. We frequently stopped to see people staring at an old log a hundred yards or so off the road (”we thought it was bear”), or at marmots emerging from their burrows (“we thought they were badgers”). One of our really great sightings, though, went unappreciated by the traffic: an isolated wetland full of sandhill cranes! As I wrote a couple of years ago, I had hoped to see the migrating sandhills down in New Mexico the March week that Deborah and I went down to see our daughter.  The cranes were reported pausing near Albuquerque along the Rio Grande up to a day before we got there! We went out right away, but they had flown on north toward their summer, breeding territories (maybe to Yellowstone!). We got a wonderfully long look at them in Yellowstone, though, and Deborah took a number of great pictures. While we were looking at them,  a couple of people drove by and stopped to check on what we were looking at. After we told them they said, “oh, just birds,” and drove on. How sad. What birds they were, indeed!




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