Scavengers

Charles Dickens
Gaffer Hexam and Lizzie fishing for corpses on the Thames.
Charles Dickens: Our Mutual Friend. Clarendon edition, 1864

“Half savage as the man showed, with no covering on his matted head, with his brown arms bare to between the elbow on his shoulder, with the loose knot of a looser kerchief lying low on his bare breast in a wilderness of beard and whisker, with such dress as he wore seeming to be made out of the mud that begrimed his boat, still there was business-like usage in his steady gaze” (Charles Dickens: Our Mutual Friend).

Scavengers get a bad rap. In Dicken’s story, Gaffer Hexam and his daughter Lizzie made a living from scavenging corpses floating in the Thames. They rummaged pockets for valuables before giving the bodies up to the authorities. But one day he found a body with papers identifying it as John Harmon, a missing man, and Gaffer was accused of his murder. Living in squalor and in thickets of thieves, scavengers soon fall under suspicion of crime.

In Tudor England a skawager was a customs collector (a more honorable occupation today, although it still causes sinking feelings in a traveler waved to their desk). Over time, the word scavenger emerged as the name for any kind of street cleaner. In removing waste and carrion they performed useful services, although it was not realized until mid-Victorian times that they were helping to safeguard the public from epidemic diseases.

I remember scavengers when I was growing up in London. Those so-called “totters” were easily recognized with their horse and cart and hand bells or from their ringing voices,

“Rags and bones! Rags and bones!” We didn’t have much household waste in the 1950s

because post-war austerity still held a vice-grip on domestic budgets. Most of our stuff was collected by “dustmen” (garbage collectors), but some choice items were saved for the rag-and-bone man, like the remains of the Sunday roast joint which we were told would be rendered by some miracle into glue or soap. Children liked to stroke the horse stamping outside their homes while the man loaded his cart, but their parents often called them indoors until the ragamuffin went away.

In the BBC sitcom, Steptoe and Son (1962-74), Harold and his irascible father Albert are in the business together, although not in any other sense together. Harold aspired to a better life, deriding Albert as “a dirty old man,” but his pretensions to middle class respectability in a rag-and-bone yard always let him down, especially with women. We laughed at the show from the comfort of our living room, and the comedy crossed the Atlantic to become Sanford and Son. It is harder for the Millennial Generation to understand the rag-and-bone trade because, after four centuries of keeping our streets cleaner and freer of disease, it had almost vanished by 1980. Its last representative in London, Alf Masterson, died in 2007.

Animal scavengers don’t enjoy any better reputation than rag-and-bone men. Hyenas, raccoons, rats, flies, dung beetles, et cetera are all regarded as vermin. And although birds are more generally loved than most other animals, vultures are regarded with particular loathing.

Riding the thermals, vultures are aerial marvels that catch the slightest uplift even on cold days; and to watch a condor hanging over the Colorado River in the Grand Canyon is a memory to savor long after the vacation. In the eastern and southern USA turkey vultures and black vultures patrol the countryside from several hundred feet scouting for carrion

turkey vulture
Turkey vulture.
Courtesy: Virginia Master Naturalists

with their sharp eyes, although it is often the turkey vulture’s exceptional sense of smell that catches the first savory whiff of a meal. Where it dives its brethren quickly follow. Black vultures are the more sociable of the two species, but both are intelligent like that other carrion-eating family, the crows, but vultures are more reviled. The sight of a venue (the collective noun for a vulture gathering) around a carcass with their naked heads bobbing in and out of the gore looks revolting, although we don’t have the same reaction to the look-alike heads of wild turkeys. Baldness makes hygienic sense for this kind of diner, and it also helps to control body temperature in hot sun. Despite a scuzzy appearance, they are finicky about preening because their lives depend on their plumage.

black vulture swiping windshield blade
Black vulture – windshield wiper swiper.
Courtesy: Virginia Master Naturalists

These “buzzards” have become more common since the Migratory Bird Treaty Act (1918) which protects them from casual shooting, and they have spread north of the Mason-Dixon Line to breed in Canada. Perhaps they are responding to global warming, but certainly to food supplies.

According to the National Highway Traffic Administration the numbers of white-tailed deer have increased from half a million in 1900 to perhaps 15-20 million today, and many of them stalk suburban gardens and public parks close to roads. Every year 1.5 million vehicular accidents with deer are reported, which cause 150 human fatalities on average, 10,000

dumpster
vulture feeding station

injuries, and a billion dollars in costs. Vultures have often cleaned the road-kill before a highway maintenance crew arrives to dispose of the carcass. They are not always so welcome, particularly at landfills and around dumpsters backing onto schools and shopping centers, but they always provide services gratis.

Vultures in India and Pakistan are not faring so well, and some are in crisis. Populations have crashed by 98% from consuming carcasses of livestock treated with the anti-inflammatory diclofenac. Despite bans on the veterinary drug, their numbers have not bounced back and the costs of losing these scavengers are tragic and still being counted. Carrion often carries disease organisms normally destroyed in the guts of vultures but which survive passage through feral dogs and rats, which become carriers and spread rabies, anthrax, brucellosis, plague, and dangerous strains of E. coli. Bites from these animals are now even more serious, and carcasses left to rot contaminate water supplies, adding to human misery and fatalities. The Parsi (Zoroastrians) mourn the vultures that used to consume their dead relatives in funeral rites, and we should grieve the loss for many reasons.

The habits of vultures have barred them from ever becoming symbols of a nation, although the American bald eagle is a part-time scavenger. Sometimes an eagle can be seen crouching over road-kill, and even in vulture company. Benjamin Franklin was unhappy when the bald eagle was chosen for the Great Seal of the USA, and in 1784 wrote his daughter Sally:

Ben Franklin
Benjamin Franklin on $100 bill

“For my own part I wish the bald eagle had not been chosen the representative of our country. He is a bird of bad moral character. He does not get his living honestly…too lazy to fish for himself… (but) the turkey is in comparison a much more respectable bird, and…though a little vain and silly, a bird of courage, and would not hesitate to attack a Grenadier of the British Guards who should presume to invade his farm yard with a red coat on.”

If the ways of bald eagles made them ill-suited to be national symbols the British lion is also a national embarrassment. But many top predators—lions, tigers, white sharks, and even piranhas—will take carrion given an opportunity. And our prehistoric ancestors probably had few qualms about carving left-over flesh from beasts that were preyed on by other animals, which brings me back to our species as the top waste-maker and recycler.

Adam Minter, the son of a Minneapolis scrap dealer, describes how the humble rag-and-bone trade has evolved into a vast and hugely profitable industry (Junkyard Planet: Travels in the Billion-Dollar Trash Trade). Canny businessmen have always known that one man’s trash is another man’s treasure. In Our Mutual Friend, the corpse that Gaffer Hexam recovered from the murky Thames was misidentified as John Harmon, the heir to a fortune made by his estranged father from collecting garbage from London streets. That reminds me of a sage saying I often heard in Yorkshire, “Where there’s muck there’s brass (money).”

Thanks to friends at the Virginia Master Naturalists (Historic Rivers Chapter) for permission to reproduce images.

Next Post: Lovely Lilah

Cold Finger

The last time we had a really cold snap like last week I dug up something unexpected in my backyard. It was not as exciting as a human skeleton, but nonetheless interesting. 

I was digging frozen turf with a sharp spade to prepare a flower bed. It was like cutting ice cream cake into slices. My hands blanched without gloves, but was better working in the cold than waiting for the thaw to turn the ground to mud.

I noticed a strange object after turning over a slice of turf.  It was the size of a hen’s egg, but as hard as a stone. Brushing off ice, it looked buffish with a yellowish stripe, and a long “process” extended from the “body.” When more ice and caked clay were removed I found another long process and two short ones attached to the corners of the body.  A French scientist would have guessed sooner they were frog’s legs.

It was a frozen wood frog, which is well-named Lithobates sylvaticus (meaning a stone that walks in the woods). Tidewater Virginia is as far south as you are likely to encounter this species, whose range extends above the frigid Arctic Circle. How this cold-blooded creature survives freezing is still an enigma, and most animals can’t.

My students in Edinburgh learned about the effects of freezing by some simple experiments with red blood cells. They diluted blood in a test-tube of isotonic salt solution, which turned pink and turbid. After freezing and thawing, the solution became so transparent that print could be read through the tube.  Before freezing, blood cells are still packed with hemoglobin which scatters light and makes the tubes look cloudy. After freezing their membranes have been perforated, which allows hemoglobin to escape and leaves the cells like transparent bags.  To confirm the theory, the tubes were spun in a centrifuge. The unfrozen cells formed a red pellet at the bottom overlaid with colorless liquid showing the cells were still intact, whereas the frozen tube was uniformly pink from dissolved hemoglobin.

Lastly, the students added glycerol at the start of the experiment, which completely prevented freezing damage.

The protective effects of glycerol were discovered by accident in Audrey Smith’s lab over

Audrey Smith (1915-1981)
Audrey Smith (1915-1981)

sixty years ago. It was one of those beautiful errors to warm a scientist’s heart.  Colleagues who remembered working with her told me that Audrey was a delightfully dotty Englishwoman who took her beloved Labradors everywhere, even opening her lab doors so they could join her at work.

Glycerol was the first of a bunch of substances that now preserve a long list of cells and tissues—blood, semen, eggs, embryos, stem cells, heart valves, skin, et cetera. They work in several ways—not simply by lowering the freezing point like car radiator fluid. When they bind water molecules or substitute for water the number and size of ice crystals that do harm inside cells are reduced. Audrey’s research team also showed they reduce the risks of cells pickling in their own brine, because salt reaches harmful concentrations when water starts to freeze.

Unlike amphibians, mammals and birds tightly regulate their body temperature, and those adapted to cold climates are protected with extra insulation and a counter-current blood supply reduces heat loss through cold feet, like penguins. Some species can turn down their internal thermostat—squirrels hibernate and bears become torpid—but none can survive whole body freezing. Hibernators wake up when temperatures fall dangerously low and start to shiver and stoke their metabolic fires.

Nakedness is a great adaptation for hot climates but no good in the Arctic. Humans generate heat by shivering and conserve it by reducing blood circulation in the skin, but for migration to the Far North more clothing and changes in behavior were needed. People with Raynaud’s phenomenon have an exaggerated vasoconstriction to chilling of their fingers and toes (penguin feet).  I do. Their digits blanch and become painful at temperatures that don’t affect others, and turning blue is a frostbite warning.

Raynaud’s can be ameliorated by drugs that reduce vasoconstriction, but in one of my more eccentric projects I tested if a herbal remedy could keep my digits warm. It was a fire water of concentrated ginger and peppers, and barely drinkable. But somehow I managed to gulp it down every day for six weeks followed by six weeks off before repeating the cycles throughout the Scottish winter. I weighed my fingernail clippings at the end of each week to the nearest milligram. If the herbal was improving my cold sensitivity I theorized that my nails would grow faster on treatment from a better blood supply to the nail bed.  There was absolutely no difference, but warming pads for hands and feet worked!

Frozen storage brings to mind episodes of Doctor Who traveling through time and space and coming back from the Planet of the Dead. And that reminds me about Cryonics in which whole bodies of legally-dead people (sometimes just their heads) are frozen in the hope that in the distant future biomedical science will restore them to consciousness. It’s a good business while customers are stiff in liquid nitrogen containers and cannot complain about the service, but I think it’s better to invest in the living.

Frozen frogs are not dead, but almost. In fact they are not completely frozen, even if three-quarters of their body water is iced-up. There is glycerol in the body, but it is not responsible for cold survival. Before hibernating, stores of liver glycogen are converted into glucose, which is another molecule that helps in cryopreservation. More importantly, ice forms in their body cavities rather than inside organs and cells, both of which shrink from partial dehydration and become supercooled. Their hearts slow and finally stop without fibrillating as ours do by only a few degrees of hypothermia.

I can’t be sure if the frog in our backyard really was alive or had frozen to death. Warming it would have given me an answer, but it might not have survived the rest of the winter without a food supply or possibly had insufficient energy reserves for  successful hibernation.  Besides, there is a You Tube video of frogs waking up to satisfy my curiosity. So I quickly returned the stone to frozen ground.

Next Post: Scavengers

Shifting Baselines

Captain John Smith
Monument to Captain John Smith, Jamestown, Virginia

In 1608 Captain John Smith led a crew of fourteen to explore the Chesapeake Bay in a shallop brought over from England in the hold of the Susan Constant.  Leaning over the side of the small craft they could see nearly four fathoms down through clear water. The bed of the estuary was encrusted with oyster reefs, enough to completely filter the bay every week, and some of the shells were large enough to serve a hearty meal. In his journal, Smith recorded, “the oysters lay as thick as stones … (there are) more sturgeon than could be devoured by dog or man … (and plenty of) grampus, porpoise, seals, stingrays, brits (?), mullets, white salmon (striped bass/ rockfish), trouts, soles, and three sorts of perch.”

The sailors must have been in awe of the bald cypress trees lining the shore like a curtain behind which a mysterious forest stretched to the horizon. The canopy was taller than any cathedral they knew in Europe, and was home to unfamiliar birds and game animals. Native people never went hungry where there was so much good fishing and hunting, and they grew corn, beans, and squash in the clearings. Smith noted the country was “very goodly.”

He never found the gold he came for, nor did he realize that the real wealth lay under his boat. It wouldn’t be harvested until the Oyster Rush in the 19th Century, which made shellfish a rarity. When they were still plentiful, their shells accumulated in the sediments leaving a record of when the Bay still teemed with life.

Fishermen and commercial watermen plowing the bay today are content with their normal catch of seafood because its original abundance stretches our imagination, if we think of it at all. We define what is normal not from the deep past, which is barely-known, but from our own experience and stories passed down by elders—“You should have seen the catches in my day, boy!” The pristine state of the Chesapeake Bay and its watershed predate human memory, and explorers like Captain Smith have left scanty records, if any. But does it really matter what the Bay looked like, because in a fast-moving world our attention is fastened on managing a man-made present and future? History is bunk, isn’t it?

Daniel Pauly disagrees. He has a theory that each generation makes its own mental map of what is normal, and consequently it can have lower expectations of richness and diversity in the environment than the previous generation if that has already deteriorated. Progressive generational myopia is called “shifting baselines,” and as a marine biologist Pauly had ocean fisheries in mind, although the concept applies generally in conservation biology and social science. To remind me of the concept I have a list of favorite shifting baselines, starting with shifting waistlines:

  • A Gallup Survey showed that Americans weigh 20 lb more than they did two decades ago, which many people thought was “just right” or normal.
  • House finches can be seen most days in Eastern Virginia, but that would not be normal for previous generations of birders.
  • Thin topsoil in my yard is normal, although I now know that a farm exhausted the land years ago when it was much richer.
  • Since average Americans watch live TV for 34 hours a week I presume they are satisfied with normal programs, though old curmudgeons who remember the hey-days of TV excoriate them.
  • Slow journeys to work in congested cities are not frustrating to everyone as we might expect because new residents accept lengthy commutes as normal.

You will have many more examples of your own, but I must get back to my theme.

There is no doubt that we have been poor stewards by polluting and overfishing the oceans. As consumers we feel the scarcity in our pockets from spiraling prices of tuna, cod, and anchovy, etc. That such a wonderful food is becoming only affordable in the rich world is a tragedy, and governments have been slow to protect collapsing fisheries, perhaps because conservation science has been blinded by the wrong baselines. Maybe a better knowledge of the original state of the environment can help to protect oceanic health and stabilize harvests because everything in a living ecosystem is linked with something else, like a spider’s web which is sensitive to changes in tension anywhere in its orb.

All things are connected.

Whatever befalls the earth

Befalls the sons of earth.

Man did not weave the web of life,

He is merely a strand in it.

Chief Seattle (1780-1866)

Chief Seattle
Chief Seattle

The wisdom of an old Native American chief who lived close to nature chimes with modern ecology. But how can we discover what stable and healthy environments looked like before they were exploited—from poring over the logs of old explorers, fishermen and whalers, or dredging up sub-fossil remains like oyster shells? The baselines that Captain Smith knew have been lost and there are precious few pristine places anymore to serve as models.

It was not however the sea but the land that alerted me to one of my own shifting baselines. I knew that most of our eastern forests are secondary or tertiary growths that have been rapidly regenerating since farming and logging started to decline here. But my error was to assume they were in the process of becoming facsimiles of the virgin forest and would again harbor the same native species with huge tree boles and towering canopies, as if we had never trammeled the land. And I thought the few remaining stands of uncut forest and reforested land protected by the Wilderness Act were pristine.

When President Lyndon Johnson signed the Act into law in 1964 he said something that used to strike a chord in me: “If future generations are to remember us with gratitude rather than contempt, we must leave them a glimpse of the world as it was in the beginning…” (emphasis added). I wish it could true, but regret I have been naïve.

I see many native trees and shrubs on my hikes that have seeded naturally—oaks, maples, hemlocks, et cetera. I fooled myself that the mixture is normal. I thought that wildness guaranteed the forest is the same as it was in the beginning, but in fact it is coming back differently. Some species that used to be dominant are now absent and replaced by foreign species. Suppression of natural wildfires (a well-meaning forestry policy) encourages the succession of fire-resistant species by others, and firebreaks create more edges where different species thrive. A history of logging and poor farming practices has often exhausted or eroded the soil, and dams and mills have altered floodplains and sediments which, in turn, alter the vegetation that grows there.

The American chestnut tree was my biggest blind spot. The tree used to inspire country folk to dub it “king of the forest,” but it is completely eliminated by blight (American Chestnut: the Life, Death, and Rebirth of a Perfect Tree by Susan Freinkel). There is now a host of introduced diseases and insect borers working their way through our pines, oak, hemlock, ash, and dogwood, and they are very hard to control. Sometimes alien species out-compete the native flora because grazing beasts and insects in their new country find them unappetizing.

George Washington
George Washington by Gilbert Stuart

If we could resurrect Captain Smith from his London grave he would tell us tales of a primeval forest he knew that is very different today. We have inklings of it from archives of the colonial era when land surveyors like a young man called George Washington were drawing plats in Virginia’s western frontier for farmers, lumbermen, and land speculators. “Witness” trees that were used as boundary markers on plats give a rare glimpse of species that grew there over two centuries ago.

land plat
A land survey plat by George Washington

And in the North-East and Appalachia sub-fossil records show that giant beech, hemlock, and spruce of the old-growth forests are now substantially replaced by maples in regenerating forests. This difference may not seem unwelcome because maples are ornamental natives, but they are less productive for supporting animal communities and the farm animals that used to run in the forest. The most productive species of all, the oak family, has declined across the range.

Gaudineer
Gaudineer Scenic Area in West Virginia. A tiny fragment of uncut, old-growth Appalachian forest

I know that it is no good fawning over the old forests, whatever they were actually like, because they will never come back. Looking back at their green light is unlikely to make a difference, and it is futile to “beat on, boats against the current, borne back ceaselessly into the past (The Great Gatsby). The land passed a tipping point of no return a long time ago when drivers of change were first released into the environment, and they continue to mold it. These changes may even accelerate with global warming.

But if the land is slipping further away from its original state, we can be more optimistic about oceans according to marine biologists. Some of them say the tide of ocean poverty can still be turned by careful management, and the Chesapeake Bay is improving, if agonizingly slowly. For eons, the Bay danced only to nature’s tune, rolling with the seasons, and generations of Native Americans who had little impact on it therefore shared a mental baseline for what they thought was normal for its waters and in the surrounding forest. Only when European colonists arrived with technologies for rapidly extracting resources was there much change, and after four centuries of exploitation Captain Smith would find the Bay strange and much diminished.

I was musing that we condemn people responsible for war, prejudice, and human bondage but rarely blame those who have spoiled the environment by industrialization, mining, overfishing, clear-cutting, and draining, eroding and poisoning land. I wondered if we excuse the pioneers because they struggled to survive in hostile territory and perhaps felt a God-given right to subdue it? Or was it because as their power of exploitation grew they didn’t realize the sea and land have limited abilities to recover? Or do we forgive them because we have benefited from their excesses. Perhaps it is a bit of all of them, but those who don’t know better can’t be held responsible for error.

I then wondered if the excuse is wearing thin on current generations and if we will be judged more harshly than we judged the past. We are no longer ignorant of our impact and are leaving plenty of evidence of our own stewardship. If future generations live in a more impoverished world than ours they will not be so blinded by shifting baselines and would justly hold us in contempt, just as President Johnson warned.

Next Post: Scavengers and Decomposers