Life Everlasting

by Bernd Heinrich

  More than a half-century ago, the renowned ornithologist Roger Tory Peterson described a similar, though perhaps less satisfying, three days at a road-killed deer carcass that he had put out in New York State:

  I hauled [the deer] to an open slope, put up my burlap blind, camouflaged it with wild grape vines. For two days I stewed in my own sweat while the carcass, thirty feet away, ripened, and flies swarmed. The vultures, at a discreet distance, sat hunched in a tall dead hemlock like undertakers waiting to officiate at a burial. On the third day I dismantled my blind. Less than three hours later a friend chanced by; as he approached, a cloud of vultures flew up. All that remained of the deer were a few scattered bones.

  Vultures are not easy to dupe, and I suspect I would have had even less luck attracting them by lying down and playing possum in the woods or meadow.

  IN COMPARISON TO the body of a mouse or a bird, that of a deer can provide an advantage to scavengers such as maggots; they thrive on the soupy byproduct of bacteria, which multiply faster in warmer temperatures, and a large body that is warm at death stays warm for a long time. In short, bacteria can get a head start. I found that out the hard way, from a lawyer and a pig.

  A lawyer in Boston had called me to offer what I thought was an exorbitant amount of money to serve as an expert witness on a murder case. For quite a long time, I had been researching the energetics of insects, and I often relied on measuring the cooling rate of freshly dead bumblebees in order to calculate the energy that live ones have to expend to keep warm. A bee’s body temperature can drop precipitously in a minute or two, but for a pig-sized carcass, the passive cooling to air temperature, even at external temperatures near freezing, might take days, since most of the heat is deep inside the animal. In the murder case, knowing the victim’s body temperature when found, which was about 98 degrees F, and extrapolating back, one could determine the time of death fairly precisely. I agreed to serve as an expert witness and decided first to collect data on the cooling rate of a human-sized pig, which would serve as an appropriate stand-in for the actual victim.

  I found a pig of the right size and told the farmer I would buy it only if I could get it when freshly killed—still at the same body temperature as a human’s. The limp, warm pig was delivered by truck and placed on the thin layer of snow in back of our house in Vermont. I stuck a thermometer in it and proceeded to record data. After two days the pig had cooled sufficiently for me to learn what I needed to know for the trial. But I was not going to waste all that good pork.

  I butchered the pig, and we cooked some of it, but it didn’t taste right—even though it was late winter and there were no flies in sight. My wife claimed that the off taste came from our chickens, which had walked with dirty feet over the pig while I was cutting it up. But I think the bad taste came as a result of bacteria growing in the long-retained body heat of this large animal, which because of the experiment had not been gutted.

  To make an even longer story shorter, my ravens got to eat some hundred pounds of pork while we ate none, and although I explained my experiment to the attorney, I was not called to the witness stand (nor reimbursed for the pig or my time). That was some expensive pig. But it taught me the hard way that a large animal cools very slowly, and if you don’t want it to go to the bacteria (if not also the maggots), you have to eat it or gut it immediately, because the bacteria have the inside track on their inside start.

  MY PIG STORY, especially the bacteria part, leads me to creatures one step up from bacteria on the carcass food chain. As I’ve mentioned, within a couple of days the deer was covered with a solid layer of writhing white maggots. Given sufficient warmth, a blowfly’s single “clutch” of 150 to 200 eggs hatch in as little as eight hours, achieve their full growth in three days, and complete their life cycle in a week. With their phenomenally fast reproductive and developmental rates, these insects can quickly take command. The blowflies, who had quickly discovered and tasted the carcass and found it good, had assured their colonization and dominance of it.

  The large numbers of maggots and their cumulative high metabolic rates would also have raised the temperature inside the carcass, speeding up their growth rate even beyond that predicted by high air temperature and slow passive cooling. Probably most of the blowflies were the metallic green ones, Lucilia sericata, the preferred species for “maggot therapy.” Maggots have traditionally been used to help heal wounds by eating necrotic tissue, and they are especially effective against Gram-positive bacteria. I suspect L. sericata may have chemical secretions as an offensive weapon against their main competitors for the meat, namely, bacteria. Nevertheless, I am not aware of anyone extracting chemicals from maggots the way we have extracted penicillin from Penicillium molds.

  Maggots may be repulsive, and the stench associated with them does not endear them to us. However, we can appreciate them. They are extensively used in forensics to determine the time of death because (depending on air and body temperature) they are the first insects to colonize a corpse.

  Aside from the medicinal and forensic value of the larvae is the fact that the adults can arguably be described as living jewels. A green blowfly’s exoskeleton is as shiny as a gem. I guarantee that if so inclined, I could sell them by the millions as ear pendants or in necklaces if they were embedded in clear plastic.

  A gem is shapeless, dead, inert matter, but each green blowfly represents exquisite aeronautical engineering; it not only flies, it has a thousand behaviors, most of which we hardly know. Like beetles, flies have no direct attachments from their power-producing muscles to the wings. As the muscles contract for the wings’ downstroke, they compress the thorax and, through lever action, cause the opposite muscles—those that power the wing upstroke—to stretch. That stretching is what causes the muscles to contract and thus stretch the downstroke muscles. This process continues, back and forth, so that the thorax virtually vibrates like a motor and the wings beat at hundreds of times per second. In some insects, like midges, they beat more than a thousand times per second—rates impossible to achieve by direct nerve impulses alone. These flies are beautiful, inside and out.

  Days after the party, more flies were still coming to the deer either despite or because of its increasing putrefaction. Flies smell (with their antennae) and can sense a carcass from about ten miles away. They walked all over the rotten meat, depositing ever more egg masses. Flies have taste receptors on the bottoms of their feet as well as on their “tongues.” As the late, great insect physiologist Vincent Dethier showed, they taste sugar, salt, sour—basically the same tastes we recognize. The flies on the deer carcass were finding and lapping up proteins, which they quickly converted to eggs—proteins are the sole food of their larvae.

  When no more open meat was available, the flies had won and the birds and coyotes had lost, but then there arrived another crew of carcass specialists, namely, beetles. Nicrophorus beetles are presumed to be able to smell a dead mouse from a half-mile away. I suspected that this insect crew might already have been working underneath the carcass, since it is well known from forensic entomological studies using pig carcasses as surrogate human ones that different species feed at different times after death. To find out if my suspicion was correct, I had to turn the deer over. It was difficult to do without gagging. But it was worth it.

  The moment I lifted the deer carcass slightly, I saw dozens of long, black shiny beetles (Necrodes surinamensis), who have parallel ridges etched into their backs. There were also staphylinids: sleek, elongate, fast-running beetles that are commonly thought to be “short-winged” but that actually have very long wings neatly folded up like a parachute under their very short elytra. About 40,000 staphylinid species have been described worldwide, and possibly twice as many are as yet undescribed. They are mostly predacious, so it was no surprise to find them scavenging on meat. They are fast runners and good flyers, and when I lifted the carcass they scattered and buried themselves in the soil debris on the surrounding ground. There were several s
pecies. One was a shiny dark blue, and another had much yellow and brown. A third was grayish with what looked like a white stripe across the back. I noted two species of silphids, flat, broad beetles about the size of a thumbnail and mainly black. One species (Necrophila americana) had yellow on the thorax; the other (Oiceoptoma noveboracense), red.

  I had expected to find many of the nicrophorid burying beetles that had so quickly visited the mouse and shrew carcasses I had set out, but after checking carefully, I found—to my very great surprise—not a one. It was hard for me to believe that they would not be attracted to deer meat. Perhaps none of the burying beetles were near that area at that time. But a road-killed chipmunk that I put out at the same time as the doe attracted two burying beetles in one afternoon. I suspect that the scent of either rot or the maggots had repelled them.

  When I returned to inspect the remains of the doe two weeks later, on August 5, I found only a few tufts of hair and the stained depression where the carcass had lain. Next to that spot, though, were two clues. The trunk of the old yellow Delicious apple tree where the vultures (and crows) had landed had the freshly grooved claw marks of a bear, and several branches of this early-maturing apple were broken. A bear had come, eaten sweet fresh apples, and dragged off the remains of the doe.

  Carcass-scavenging beetles found under a deer carcass. Top: two (of more than 46,000 species identified) rove or staphylinid beetles; bottom right: Necrodes surinamensis; bottom left, Oiceoptoma noveboracense and Necrophila americana.

  THE FOLLOWING LATE April I found a dead bull moose about two kilometers from the site where I had left the doe. A bull moose probably weighs ten times as much as a white-tailed doe. This one looked emaciated; it had apparently died from complications of moose tick disease, a common cause of death in these woods when winter temperatures are not low enough and the snows do not last long enough to suppress these parasites. If wolves had been present, there would not necessarily have been many more moose deaths, but moose weakened by the tick disease would probably have died sooner, because they would have been the predators’ prime prey.

  I found the moose a day or two after it had dropped in thick forest next to a small brook. Coyote tracks surrounded it, and the coyotes had chewed through its thick hide to make a hole in the throat. A raven had already fed there, leaving white droppings on the hide. Other ravens came to feed as the coyotes enlarged the hole. Later at least a dozen turkey vultures monopolized the carcass, and then the maggots “cleaned up” after them. A couple of weeks later, a pair of ravens remained after the coyotes and vultures were done; they came daily to turn the leaves surrounding the carcass, presumably picking up maggots, fly pupae, or other insects.

  When all that was left was a skeleton with dried hide covering part of it, a black bear came and dragged the remains a short way downhill. After two weeks, I found little more than a pile of hair where the animal had fallen and the vertebral column and skull some distance from that. A porcupine was eating the still-fresh bone, gnawing it off in patterns that looked like a magnification of the tooth marks mice might leave on cheese. No vultures remained despite a lingering smell. Why were the vultures no longer attracted? There was no more meat, but how would they know that without checking? Do the maggots emit a scent that repels even vultures, or are they repelled by the scent from bacterial decay?

  IN THE RECYCLING world of nature, there is much redundancy and always backup. The recycling process may start with a car or ticks, then employ scavenging birds, move on to flies, then beetles, and finally bacteria or, in the case of our deer and moose, a bear. Had the bear not taken the deer carcass after the flies were through, it would have been visited by swarms of dermestid beetles. These beetles, of which there are 500 to 700 species worldwide, come to a carcass when the remains are dry and well past the decomposition stage. They eat the remaining wool, feathers, gristle, fur, and skin—everything except bare bone. For this reason they are often used to clean skeletons in museums. In a forest, rodents as well as deer would gnaw on them to get their needed calcium, and the bones become covered by leaves. In my forest I find deer skulls but seldom more; the skulls always last the longest. No animals larger than moose inhabit the Maine woods. Clearly, though, the local undertakers are up to the task of disposing of even a moose in relatively short order.

  But what is the undertaking process, I wondered, for something almost colossal in comparison, such as an elephant?

  The Ultimate Recycler: Remaking the World

  The hand is the cutting edge of the mind . . .

  The most powerful drive in the ascent of man is pleasure in his own skill.

  —Jacob Bronowski, The Ascent of Man

  WE HAVE SEEN THAT MANY SPECIES ARE BOTH HUNTERS AND scavengers—the two roles share the same goals and many of the same tools. This was true for early humans: the more effective we became as scavengers, the more we hunted, and vice versa. Nowhere is that proven more dramatically than with the most challenging of prey: elephants. Humans are the only predators on earth who can consistently prey on them, open them, and also affect their existence. On land we are to the elephants what the sleeper sharks and hagfish are to the whales of the ocean depths: the ultimate recyclers. How we became that is embedded in the history of our species. Our relationship to the elephant defined our path to becoming the earth’s ultimate agent for processing through the maw of our collective metabolism almost everything that grew and much that grows. Once we had learned how to access the live meat of elephants, we were equipped with the brains, the brawn, and the social organization to tackle almost anything that came within our reach. The questions I am leading up to are whether we evolved as hunters or scavengers from the start, what roles we played and still play as undertakers, and how tortoises and elephants hold the answers.

  THE DEBATE ON whether we started as hunters or scavengers after we (and other apes) diverged from a common ancestor has been a heated one, and it predates a half century. My only “data point”/anecdote that bears on it, and that may bias my thinking, occurred in Kenya’s Amboseli National Park around 1970, when I had the privilege of tagging along behind a troupe of human-habituated baboons with a graduate student who was studying them. The baboons were grazing, but after only a couple of hours we saw one flush a hare. It escaped the clutches of the first baboon, only to run into those of another in the large troupe. It was then quickly dispatched and monopolized by a large dominant male, although others got pieces of this prize before it was totally eaten. The “hunt” had seemed haphazard and success almost accidental, due mainly to the largeness of the group. However, another student of baboons near that time and place, Shirley C. Strum, found that baboons regularly hunt for meat.

  Anthropologist Craig B. Stanford has subsequently championed the “hunting hypothesis” for early man in his book The Hunting Apes. He had studied the hunting behavior of chimpanzees, our closest living relatives. Chimps of some troupes regularly and systematically hunt monkeys and other prey. They eat raw meat often and with relish, consuming skin, bones, and all. They have not been observed to scavenge. Stanford points out that the males, who do most of the hunting, engage in a lot of politicking while sharing their meat. The social nature of hunting and sharing, perhaps linked to sexual privileges, may have been pivotal in our branching off from apelike ancestors to become specialized as hunters. Hunting favored social cooperation, the skills and intelligence that became human hallmarks.

  From our present perspective in an industrial civilization, “hunter” is not the first term we would choose to characterize ourselves. But looking back in time only a moment, consider America in the nineteenth century. In John James Audubon’s “Missouri River Journals,” which he wrote between June 4 and October 24, 1843, we see a part of America that was thinly populated by a few frontiersmen and Indian tribes. On June 9 Audubon wrote: “We saw three Elks swimming across it [the Little Missouri], and the number of this fine species of deer that are about us now is almost inconceivable.” On August 11: “
it is impossible to describe or even conceive [his underlining] the vast multitudes of these animals [bison] that exist even now, and feed on these ocean-like prairies.” Hardly a day went by that Audubon and his companions did not shoot several bison, deer, elk, antelope, or wolves.

  It is difficult to believe that within several decades we had almost totally destroyed that world. Weaponry was important; the rifle helped exterminate the buffalo. But hunting ingenuity did not depend on rifles alone. Audubon described how many wolves were caught simply on baited fishhooks. Buffalo were chased onto ice, where they were helpless and could be stabbed. They were also caught in pens, “especially [by] the Gros Ventres, Blackfeet, and Assiniboins,” who made impoundments of logs and brush with funnel-shaped passages leading into them. The bison were lured and then chased in. A young man, “very swift of foot, starts at daylight covered with a Buffalo robe and wearing a Buffalo head-dress,” and he “bellows like a calf, and makes his way slowly towards the constricted part of the funnel, imitating the cry of a calf, at frequent intervals. The Buffaloes advance after the decoy,” and hunters yell and advance behind them. Then all are destroyed.

  The buffalo abundance would perhaps have been vastly reduced even before the Europeans came, if the various tribes—Arikaras, Sioux, Assiniboins, Gros Ventres, Blackfeet, Crow, and Mandans—had not been constantly at war with each other and thus never became as numerous as the Europeans. It might seem that no number of people could eat the vast quantities of meat from the millions of large animals killed, and in fact they didn’t. The frontiersmen often took only the tongue and the warm brains and liver, which they often ate raw. As Audubon described the scene, “Now one breaks in the skull of a bull, and with bloody fingers draws out the brains and swallows them with peculiar zest; another has now reached the liver and is gobbling down enormous pieces of it; whilst, perhaps, a third, who has come to the paunch, is feeding luxuriously on some—to me—disgusting-looking offal.” Audubon wrote of the searing heat, with temperatures often in the 90s and sometimes over 100 degrees. Meat would not keep fresh for hours in such heat, so a nomadic hunter had to kill daily and leave most of the meat to the wolves and the ravens.