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Showing posts from February, 2012

Evolution of the Horse

The common ancestor of Perissodactyls (horses, rhinos, tapirs) appeared in North American during the Paleocene, about 60 million years ago (MYA). The first known member of the horse lineage was Hyracotherium, formerly known as Eohippus, a small deer-like herbivore of subtropical forests that fed on tender vegetation and fruit. Appearing in the early Eocene, some 55 MYA, this dog-sized mammal evolved through a series of early horse ancestors to Oligocene forms such as Mesohippus (37 MYA) and Epihippus (30 MYA) that began to emerge from the forest to take advantage of newly evolved and nutritious grasslands; in concert, their teeth took on traits vital to grazing and their dominant third toe would evolve toward the modern hoof.

Diversification in the early Miocene led to Parahippus, a pony-sized ancestor, and Meryhippus (17 MYA), the first true grazer and fleet, horse-sized member of the lineage. Meryhippus diverged into at least three groups, one of which, Hipparion, was the first an…

Deadly Romance

No, this is not the title for another TV murder mystery. Rather, it is an acknowledgement that we have entered the peak roadkill season, as the carcasses of raccoons, opossums and skunks litter our scenic byways. Soon to be joined by lovesick groundhogs, these small mammals are roaming about in response to their mating instinct, following trails of pheromones across the late winter landscape. Primarily nocturnal, these determined suitors sometimes look for love in the wrong places, even on our concrete ribbons of death, and too often meet an inglorious demise.

Were it not for our roads and vehicles they might be culled by owls, fox or coyotes; in fact, fresh carcasses may be claimed by natural predators while others provide sustenance for vultures and less conspicuous scavengers. Fortunately, these small mammals are prolific and the highway slaughter has little impact on their populations.

However, it is disturbing to realize that these victims are often lured to their deaths by t…

Flamingos & Grebes

Watching a flamingo navigate the shallows of an ephemeral lake, one would surely conclude that it is closely related to storks, herons and ibis; yet, placing this bird on the tree of avian evolution has long been a subject of controversy. By late in the 20th Century, fossil evidence from across the globe seemed to suggest that flamingos are a hybrid between shorebirds and waterfowl; indeed, they harbor the same feather lice that are found on ducks and geese. The fossil evidence also revealed that, despite their current concentration in tropical and subtropical life zones, flamingo species were widely dispersed throughout temperate regions before the Pleistocene Ice Age.

Then, within the past decade, molecular geneticists discovered that flamingos are, in fact, most closely related to grebes. This finding sent a shock wave through the world of avian biologists, especially given the obvious differences in the appearance and behavior of those bird groups. Nevertheless, morphologic s…

Pleistocene Plant Revival

A recent article in the New York Times reported on the successful revival of a narrow-leafed campion from deposits of the late Pleistocene. Russian paleontologists had discovered seeds and fruits of the plant in river bed sediments of eastern Siberia, apparently buried by a ground squirrel; radiocarbon dating of the seeds indicated that they were first entombed about 32,000 years ago, when humans were displacing Neanderthals in Europe and Denisovans in eastern Asia.

While efforts to germinate the seeds were unsuccessful, the scientists were able to thaw and culture placental cells from the fruit, yielding mature plants that flowered and produced new seed; these descendent seeds were then planted to yield another generation of campions. According to the article, the Russian scientists speculate that the Pleistocene plant material was buried in soil just above the permafrost layer, favoring its prolonged viability; in addition, sugars and phenols within the plant tissue served as an a…

Eastern Sandhill Cranes

Most American birdwatchers associate sandhill cranes with the Great Plains and Western U.S., having seen large flocks at staging areas, such as the Platte River in Nebraska or the San Luis Valley in Colorado, or at wintering grounds in California, New Mexico or Texas. But there is a large and growing eastern population of sandhill cranes, composed primarily of the greater sandhill crane subspecies.

These cranes breed in the vicinity of James Bay, Canada and around the Great Lakes, from Minnesota and Wisconsin to Michigan and northern Ohio. On their migrations to wintering areas from southern Georgia to central Florida, they use two primary staging areas: the Jasper-Pulaski State Fish & Wildlife Area, in northwest Indiana, and the Hiwassee Wildlife Refuge, just NNE of Chattanooga, Tennessee. Of course, migrant flocks may be seen in wetland areas and agricultural fields anywhere between their breeding and wintering areas and the cranes may shorten their travels if mild conditions…

Winter's Comeback

My office at the medical school commands a broad view to the west and, at noon yesterday, I looked out on an idyllic scene; bright sunshine, blue skies and a warm, southwest wind brought the look and feel of mid spring to mid Missouri. However, on closer inspection, I could see a swath of haze across the northwestern horizon and, within a few hours, a wall of clouds had taken its place.

By late afternoon, most of the sky was covered with a thick, gray overcast and a chilly, west wind had replaced the mild southerly breeze; our noontime high of 65 degrees F had dropped into the low fifties. Overnight, as the cold front passed to our east, strong, northwesterly winds rattled the windows and sent a deep, intermittent roar through the barren trees. While the snowfall will remain to our north and east, we won't get out of the forties today and a gusty north wind will make it feel much colder.

The weather gyrations of spring have begun, as winter and summer battle for the Heartland. …

The Armadillo Army

Distantly related to sloths and anteaters, armadillos evolved in South America during the mammal explosion of the early Tertiary Period, some 50-60 million years ago. When the Isthmus of Panama formed, about 3 MYA, some species moved into Central America; today, all but 2 of the 20 modern species of armadillo inhabit South America and the nine-banded armadillo is the only one found in the United States.

Since crossing into Texas in the late 1800s, nine-banded armadillos have rapidly expanded their range; limited by dryness and poorly equipped to survive in prolonged cold, these prolific mammals can be found from western Oklahoma to the Atlantic Seaboard and from southern Kansas, southern Missouri and South Carolina to the Gulf Coast. Favoring streamside habitat, the armadillo army has spread along the Arkansas and Lower Mississippi Valleys and inward from the Gulf and Southern Atlantic Coasts via rivers and streams of the broad Coastal Plain; they have also been transplanted to some…

The Caffeine Pushers

The latest drug craze in the U.S., promoted by numerous television commercials, is the use of high dose caffeine. Offered for consumption, inhalation or absorption on the tongue, these products are marketed as quick and easy solutions to morning or afternoon fatigue.

Of course, caffeine is a stimulant and, like all drugs, has potential side effects that range from mild restlessness to fatal cardiac arrhythmias. It is known to cause tachycardia, hypertension, headaches, muscle cramps, diarrrhea, nausea, stomach irritation, anxiety, tremors, excessive urination, insomnia and tinnitis, all of which vary with the individual; caffeine is also known to exacerbate glaucoma, osteoporosis and irritable bowel syndrome. Many people who regularly use high doses of caffeine develop withdrawal symptoms if the drug is discontinued; these symptoms, however mild, encourage continued use.

Perhaps the most disturbing side effect of this latest drug craze is the social reinforcement that pills, potions…

Sea Eagles

Members of the genus Haliaeetus, sea eagles inhabit all of the continents except South America and Antarctica. Genetic studies indicate that our eight modern species are descendents of an evolutionary line that likely arose in the Oligocene, some 25-30 million years ago.

Northern sea eagles, all of which have yellow beaks, eyes and talons, are represented by the bald eagle of North America, the white-tailed eagle of Greenland, Iceland and northern Eurasia and the massive Steller's sea eagle, which inhabits the eastern coast of Siberia. The African fish eagle is found across sub-Saharan Africa while its endangered cousin, the Madagascar fish eagle, lives along the western coast of that island nation. The dull brown Pallas's fish eagle inhabits central Asia, the white-bellied sea eagle has colonized the coast of southeast Asia and Australia and Sanford's sea eagle lives in the Solomon Islands; the latter two species are thought to have diverged in the late Pleistocene.

Al…

Crocus Days

The crocuses have been blooming in Columbia over the past week, a bit ahead of schedule due to our mild winter. Their appearance, together with that of other early bloomers, such as snowdrops, periwinkle and hyacinths, is always a welcome sight, indicating that the depth of winter has surely passed.

Nevertheless, these precocious flowers signal the onset of an annual period during which the weather is especially challenging across the American Heartland. Here in Missouri, we enter the gray, damp, raw days of late winter and early spring, characterized by wet snow, cold rain and a muddy landscape. And out west, at our Littleton, Colorado, farm, we face the heaviest snowfalls of the year as the upslope storms of March and April descend on the Front Range.

Like the arrival of snow geese and the frenzied calls of chorus frogs, these crocus days are bittersweet, an early sign of spring but a reminder that the sunny, mild, heart of the season is still a month or more away. Until then, w…

The Nature of Conifers

Conifers, represented by 200 species in North America and more than 600 worldwide, evolved in the Pennsylvanian Period, some 300 million years ago; indeed, they have colonized our planet twice as long as flowering plants, which appeared in the Jurassic. Many of our modern conifers have graced the planet for 100 million years or more and now include the tallest (California Redwood), largest (Giant Sequoia) and longest-lived (bristlecone pine) trees on Earth.

Characterized by needle-like or lace-patterned leaves, conifers produce male and female cones which, depending on the species, may occur on the same plant. The male cones release a copious amount of pollen which, carried by the wind, fertilizes the female cones; seeds are born on scales of the female cone and are dispersed by birds, red squirrels, chipmunks or by the cone itself when it falls to the ground; in some species, such as lodgepole pines, the heat of wildfire is a crucial step in releasing the seeds. Though most coni…

Snows at Dusk

As I walked home last evening, the sky was clear and the temperature hinted of spring. University students sauntered about in shorts and T-shirts and the orange glow of sunset only served to augment the festive atmosphere. It may have been February but April was paying a visit.

Bird song had begun to intensify, green shoots adorned the flower beds and the aroma of wet soil scented the evening air. Then, as I neared our home, the unmistakable call of snow geese echoed from the darkening sky and I looked up to see two wavering lines of those vocal migrants. Headed northwest, toward the Missouri Valley, they'll likely spend a few days at Fountain Grove, Squaw Creek or some other refuge along their ancestral highway.

Though flying into the teeth of winter, the snow geese carry the message of spring to earth-bound, winter-weary humans. Our faith will be tested by more ice and snow over the coming weeks but those hardy travelers, unencumbered by calendars and weather forecasts, kno…

Red Crossbill Diversity

Red crossbills are nomadic finches of North America that roam the coniferous forests of southern Alaska, southern Canada, New England, the upper Great Lakes region and the mountain corridors of the West, from British Columbia and Alberta to Mexico. Monogamous, their breeding is prompted by an abundance of food and may occur during any season of the year; in good years, multiple broods are raised. Feeding primarily on the seeds of conifers, their crossed bills have evolved to pry open the cone scales, allowing them to extract the seeds with their tongue; red crossbills also feed on a variety of non-conifer seeds, berries and insects, especially aphids.

Irruptive, red crossbills often wander from their breeding range, especially during the winter months, and may turn up almost anywhere in the Continental U.S.; indeed, they have been discovered nesting as far south as the pine woods of Georgia. In recent decades, ornithologists have identified eight subspecies of red crossbills, which…

Erosional Remnants

Mention erosional remnants and we tend to think of sea stacks, free-standing buttes and other solitary rock formations that have withstood the forces of wind, water and ice. Some of these landforms, especially mesas and buttes, are protected by a resistant cap of basalt or other non-porous rock while others are igneous plutons or laccoliths, uncovered as their encasing sediments have eroded away.

In reality, all natural landforms are erosional remnants, the current product of underlying geology, tectonic forces and erosion, modified by climate and vegetation. Highlands may represent areas of uplift, volcanism or resistant geologic strata but remain subject to the forces of erosion and, eventually, will wear down to a level plain. Stream valleys and canyons, while seemingly stable during our brief lifespan, are continually molded by floods, deposition, landslides, rock falls and periods of drought; depending upon the interaction of these factors, they may deepen, widen, clog with er…

Madagascar's Cyclone Season

Madagascar, the fourth largest island on Earth, lies off the southeast coast of Africa, in the western Indian Ocean. Oriented northeast to southwest, the island is bathed by southeasterly trade winds throughout the year, producing copious precipitation along its eastern coast; indeed, some areas receive up to 150 inches of rain. Since highlands run down the center of the island, the western coast of Madagascar lies in their rain shadow and its climate is much drier.

The wet season in Madagascar runs from November through April, encompassing the warmest months of the year. During the Southern Hemisphere summer, the Intertropical Convergence Zone (ITCZ) drifts south from the Equator and, from December through early March, it crosses the northern half of Madagascar. Along this zone, northeasterly and southeasterly trade winds merge, producing lift and bands of thunderstorms; the colliding winds also produce wind shear at the surface and, if upper level winds are calm, cyclones may de…

The Dark Side of Love

On this annual, commercialized tribute to love, it is appropriate to acknowledge that there is a dark side to this complex human emotion. As most of us come to learn, love is not always a two-way street and unrequited love is one of the more devastating of human experiences.

While the character of romantic love evolves through the course of a prolonged relationship, molded by the trials and tribulations of human intimacy and family responsibilities, the intensity of unrequited love endures, locked away in the safety of our mind. Cleansed of defects by the protective nature of human memory, its glory is sustained and embellished over the years and its loss can become a source of regret and self-indulgence, especially for those whose self-esteem is closely tied to relationships.

Welling up on certain dates or ignited by specific triggers such as songs, movies or places, this unrequited love can become an obsession, menacing our lives and, in some cases, leading to depression. While t…

The Human Swarm

In this era of social networking, facilitated by Facebook, Twitter and those ubiquitous smart phones, a large segment of our society has become a human swarm, communicating via emails, tweets, texting, instant messaging and online comments. Spurred on by friends, journalists, broadcasters, sports commentators and a host of media celebrities, many of us have become accustomed to sharing our lives and thoughts with the internet universe and, unfortunately, often rely on those connections to feed our self esteem.

While social networking surely has its advantages and while many participants are able to balance this activity with their family, educational and employment obligations, others seem to be obsessed with these communication technologies, putting their privacy and personal welfare at risk. Of course, as we often learn or experience firsthand, this obsession may lead to accidents and injuries, the result of constant distractions from the almighty cell phone. In addition, this de…

Frigid Sunshine at Eagle Bluffs

As we arrived at Eagle Bluffs Conservation Area this morning, a large flock of snow geese passed overhead, shimmering in the bright morning sun; it was 12 degrees F. Most of the shallows had frozen over but open pools attracted a mix of wintering ducks, including mallards, gadwalls, coot, green-winged teal, ring-necks and lesser scaup; scattered flocks of Canada geese rested on the ice and a group of pied-billed grebes dove for their breakfast.

Several more flocks of snow geese crossed the refuge during our visit, moving north along the Missouri River Valley, as did a large flock of greater white-fronted geese. Five sandhill cranes had gathered on a wooded island and at least fifty American white pelicans huddled on a sandbar near the south end of the preserve. Ring billed gulls swirled above the open pools, northern harriers zoomed across the dormant crop fields, great blue herons perched in the morning sun and an immature bald eagle soared overhead, oblivious of the frigid air.

S…

From Snow to Snows

As we left the snowy landscape of Metro Denver yesterday morning, a full moon gleamed above the Front Range. Once past the Palmer Divide, the snow cover gradually diminished and, except for residual drifts along the highway, had disappeared by the time we entered Kansas. However, as I discussed on February 6, the snow blanket reappeared near Wakeeney and then steadily vanished as we descended toward Hays.

For the remainder of our journey, a brown landscape and gray sky set the scene; only the aerial ballets of starlings, the agile swoop of harriers and the reliable presence of red-tails broke the monotony. Then, just east of Russell, Kansas, my first glimpse of snow geese during this "spring" migration season erased my boredom as a wavering flock crossed the bleak winter sky, headed toward their Arctic breeding grounds. A second flock appeared near Salina and a third, much larger flock graced the sky in eastern Kansas.

Darkness negated any sightings in Missouri but, over…

Flying with Pterosaurs

Since heavy snow still covers most of the Front Range trails, we opted for a visit to the Denver Museum of Nature & Science today. Long famous for its wildlife dioramas, this magnificent institution has recently received kudos for its recovery of numerous Pleistocene fossils from a lake bed near Snowmass, Colorado; the skeletal remains of mammoths, mastodons, ancestral camels, ancestral bison and numerous other animals were unearthed last summer before the reservoir was refilled.

Today, we arrived just in time to see an IMAX film produced by National Geographic and narrated by the renowned naturalist, David Attenborough. Given the odd title of The Flying Monsters, apparently chosen to attract young visitors, this 3-D film covered the natural history of pterosaurs, from their initial appearance in the Triassic, some 200 million years ago, until their disappearance at the end of the Cretaceous, 65 MYA. Thought to have evolved from lizards that used webbed limbs to glide between t…

Snow on Snow

Leaving a nearly snowless winter in Missouri, we arrived at our Littleton farm and found it adorned with more than 15 inches of white powder; fortunately, my Tacoma pickup was able to navigate the long, uphill driveway and it was just a short trudge to the backdoor.

Out on our property, Townsend's solitaires, robins and bushtits feasted on juniper berries while chickadees, flickers and house finches moved among the bare deciduous trees, undaunted by the heavy snow. Our resident fox and raccoons may den up for a few days but we'll soon see their tracks across the blanket of white. Down on the South Platte, ducks and geese crowded the river, feeding along and beneath the relatively warm, open waters.

Another cold front passed through Colorado overnight and, though only a dusting was expected, five more inches were left behind. Enjoying a snowy winter landscape for a change, my wife and I took a walk through the residual flurries as the clouds began to dissipate and patches …

High Plains Upslope

On my frequent travels between Missouri and Colorado, I have often noticed that, following a snowstorm, the Wakeeney, Kansas, area receives more snow than areas to its west or east on I-70. Assuming this must represent an upslope phenomenon, a reflection of the local topography, I examined a map of the region after yesterday's journey reinforced my past observations.

In fact, Wakeeney sits on the east edge of the High Plains at the west end of a topographic wedge in which the elevation is gradually rising from east to west. A prominent ridge just south of Hays, Kansas, is an erosional remnant of the High Plains, dividing the watersheds of the Smoky Hill River, to its south, from that of Big Creek to its north. In similar fashion, though not as visible from I-70, another eastward extension of the High Plains divides the Big Creek watershed from that of the Saline River, to the north of that ridge. Both of these ridges merge near Wakeeney and the rolling terrain between them cli…

Human Hybridism

While evangelicals will surely stick to their Adam and Eve story, DNA technology has greatly advanced our understanding of evolution and, in recent years, has uncovered the fact that most humans are hybrids. The last (to date) in a long line of hominids to walk the Earth, our species appeared in Africa about 130,000 years ago and began to disperse from that Continent about 80,000 years ago. However, earlier hominids had colonized Eurasia long before we left our homeland.

About 600,000 years ago, the lineage that would lead to humans split from one that would culminate in Neanderthals and their close cousins, the Denisovans. Based on DNA studies, these hominids diverged genetically and geographically about 350,000 years ago as Neanderthals spread into Europe and Western Asia while Denisovans occupied Eastern Asia, from Siberia to Indonesia. The latter group was unknown until a few fossils were discovered in a Siberian cave just two years ago; cool conditions within the cave served …

A Spring Storm in Mid Winter

Here in central Missouri, we awoke to clear skies and temperatures in the low 40s (F), with light southeast winds. But to the west, a wall of dark clouds stretched across the horizon, the leading edge of a massive storm system that is centered over the Southern Plains. Ahead of the storm, Gulf moisture is flowing northward across the Heartland and, as the system approaches, bands of rain will move in from the west, a product of lift, atmospheric moisture and the clash of air masses. Rain should develop in central Missouri by early afternoon and is expected to persist for 24 hours or more, a welcome development for our parched landscape.

On the northwest side of this storm, the Gulf moisture is being whipped toward the Front Range as counterclockwise winds swirl around the central low. These upsloping winds cool as they rise in elevation and heavy snow is falling across Metro Denver, the foothills and the adjacent plains; up to 20 inches are expected in the city with higher amounts…

Natural History of Elephants

Sixty million years ago (MYA), a common ancestor gave rise to three orders: Sirenia (represented today by manatees and dugongs), Hyracoidea (represented by the hyrax) and Proboscidea, which encompasses all extinct and living species of elephants and their close relatives. Moeritherium, a pig-sized mammal that lived in North Africa about 50 MYA, is the earliest known proboscidean and the Deinotherium line diverged 10 million years later; this lineage culminated in a massive elephant-like creature that spread throughout Eurasia and Africa during the Miocene and became extinct by the onset of the Pleistocene (2 MYA).

The Paleomastadon line emerged in North Africa about 34 MYA; Gomphotheriums split from this primary lineage about 25 MYA, giving rise to the Mastadon line about 20 MYA. The main group of Gomphotheriums died out by the end of the Pliocene (2 MYA) but the mastodons lived through the Pleistocene, occupying Africa, Eurasia and North America. Primelephas, the first member of t…

Nature & Government

While I am a social liberal, I am a fiscal conservative and I actually agree with many Republicans that our government is bloated and inefficient. I support simplification of the tax code, elimination of earmarks and enforcement of term limits. Unlike many conservatives, I also favor an end to corporate welfare and strongly support efforts to cut our outrageous defense budget.

On the other hand, history is replete with evidence that the federal government plays a crucial role in the protection of both civil rights and the health of our natural environment. Big business, driven by greed and focused on profits, has not demonstrated the capacity to protect either the consumer or the environment without oversight by federal agencies. From a naturalists point of view, governmental regulations have been vital to the welfare of natural ecosystems throughout this country and across the globe.

Too often, Americans jump on the bandwagon of anti-government rhetoric without giving proper cons…