Or what do bacteria, beetles, flies, ravens and fungi have in common?
And now, since I have taught that things cannot
Be born from nothing, nor the same, when born,
To nothing be recalled…
Lucretius, On the Nature of Things (50BCE)1
The Roman poet Lucretius writes at great length on a topic that 2,064 years later, still haunts us: what is death—the end or the beginning? If you are a sexton beetle, the death of a mouse is cause for celebration, including a pheromone producing dance, a mate, a house and babies. From bacteria to coyotes, death signals food and reproductive possibilities.
Scavengers are defined as those that live only on dead organisms—predators, on only what they kill. Very few animals are strictly one or the other. Scavengers are nature’s undertakers, providing invaluable natural services by redistributing the material of life. Can you imagine a world where dead bodies piled up without magically disappearing, as they seem to do now?
The size of a dead body determines who the disposers will be and how they will do it. Temperature also plays a huge role in determining the scavenger. At low temperatures, bacteria stop reproducing, insects cannot fly, and vultures, with their naked necks would freeze if they didn’t head south. In winter, meat can stay fresh longer and feed larger animals—coyotes, cats, foxes, ravens, jays, chickadees, woodpeckers, nuthatches. We think of burial as a way of hiding away a body; when nature’s undertakers dispose of a body, it is not to get rid of it, but to keep it safe for later use.3
Beetles of the genus Nicrophorus—roughly translated from Greek as “lover of death,” are also know as sexton or burying beetles; they not only bury small dead animals (never their own species) but they mate on them, and make a home for their young larvae within the decaying carcass.
Soon after an animal dies it begins to decompose, as gut microorganisms are no longer kept in balance by the animal’s defense mechanisms. A faint odor very quickly attracts botflies and beetles looking for food as well as a place to lay eggs. The male sexton beetle has a scenting organ for smelling this odor of death. After locating the bird or rodent he does what looks like a handstand, lifting up his rear, as he emits a scent from a gland near the anus. If a female receives the scent, she will fly to him and mate. If a male arrives first, the two will fight for possession of the carcass.
The mated pair must then move the carcass to soft earth for burying; since they don’t have grasping feet, they lie underneath on their backs and move the body along with their legs. Upon finding a spot that is soft enough to be dug, the two begin digging by scraping out the sides, allowing it to fall into the hole. They cover it with several inches of soil.
The carcass, which has grown soft by now, is rolled into a ball while the pair removes hair or feathers. The beetles spray the body with a powerful antibiotic found in their anal gland—this kills bacteria and fungi and deters botflies. The female lays her eggs in dirt nearby, which will hatch into larvae in a few days. When hatched, they crawl to the carcass and settle into the hollowed out spot on top. The adult beetles make squeaking noises before feeding the grubs bits of meat. Like baby birds, the young raise their heads with open mouths to be fed. After a week or more, the grubs are feeding themselves, although they may still gather together for communal feedings. Now, it is time for the male to crawl above ground to find another carcass and possibly another mate. The female remains behind. The grubs will eventually burrow into surrounding soil and pupate. The mouse has been reduced to bones.
There is much competition for carcasses; sexton beetles have hitchhiker mites that help out. These specialized mites hide under the beetles’ elytra (wing covers) most of the time, but upon landing on a dead animal, the mites disembark and scour the body for fly eggs, which they kill. Before the beetle takes flight again, the mites crawl back on, hiding under the elytra—a mutualistic relationship that benefits both species.
Nicrophorus beetles turn their red and black elytra over when they fly, some showing a yellow band; this adaption enables them to resemble a bumblebee when flying and affords some protection against insectivores. 4
Sometimes it is the green botfly, Lucilia sericata (or one of the other hundreds of species of botflies) who will colonize a carcass before beetles can claim it. Bacteria begin the process of decomposition thriving in the warm carcass. This emits an odor, the chemical of putrefaction, ethanethiol, known as the smelliest substance on earth—the same odor added to propane gas used to alert us to leaks. Flies, who smell with their antennae, can scent a carcass from ten miles away. They have taste receptors on their “tongues” as well as on their feet. They will lap up the proteins of a soupy carcass and turn this energy into eggs. Protein is the sole food of maggots. A botfly clutch of 150 to 200 eggs will hatch in as little as eight hours, become fully grown in three days and finish their life cycle in a week. Flies and maggots have such high metabolisms, they raise the temperature of the carcass, further facilitating maggot growth. Green fly maggots are preferred for “maggot therapy,” used to help heal problem wounds in humans. They eat necrotic (dead) tissue and are especially effective against Gram-positive bacteria (retains purple dye as classified by Gram’s bacterial classification test).
Lucilia sericata is also used in forensics to determine time of death because they are often the first insects to colonize a corpse if air and body temperature are suitable. 5
Ravens once were and may still be the most important carcass consumers in the Northern Hemisphere—the “carcass specialist” of the crow family. The recent northward expansion of the coyote has benefited the return of Corvus corax. Lucky is the raven that comes upon a fresh winter-weakened deer killed by coyotes. Ravens require a carcass to be opened up before they can have access to the meat. They also must start nesting early in order to raise their young to self-sufficiency by the following winter. Social, intelligent, and very playful animals, they may gather together to roost at night, or at a carcass, but rarely eat in front of each other. Trying to haul off as much meat as they can, flying a kilometer or more away, ravens cache away meat in the snow or under leaves. They are notorious for stealing each other’s food, watching for caching places, unburying each other’s stores, even stealing food away on the wing. Smaller mammals find much of this buried food, and so in this way, the raven feeds a whole community.
Scavenger birds were far more common in North America than they are now. In the days before the arrival of man, when mega-fauna grazed throughout the continent, fallen beasts fed an entire web of life. Homo sapiens, the large brained hunter-gatherer arrived as the last glaciers retreated, bringing their Clovis point spears with them. Extinction soon followed for most of the huge beasts. The debate goes on as to weather they suffered from climate change or hunter-gatherer’s hunger. John James Audubon in 1843 wrote about the “vast multitudes of these
animals (bison) that exist even now, and feed on these ocean-like prairies.” Two decades later, they were rare—man with his new tool, the rifle and with an agenda of reducing the Indian’s population, had killed off most of the bison. 6
It was common practice out west for ranchers to lie out poisoned carcasses to kill wolves; birds ate at those carcasses as well and suffered greatly from this practice. Even today we are poisoning scavengers with rodenticides, anti-coagulant (blood thinners) poisons used to control rats. The rat does not always die in the wall, but crawls out to be picked up and eaten by other scavengers.
Today, the beasts that graze our lands are intentionally grown as food for humans and their pets, not scavengers. We consume all of what we raise, using every part of the animal for everything from steaks to dog food, shampoo, bone meal and leather. Fortunately, ravens seem to be making a comeback. Poisoning of wolves out west has been outlawed, although enforcement is sketchy; in the Northeast, large deer populations and a new push north by coyotes are helping with the raven’s return. 7
In Canada, however, mining of Alberta tar sands and the resulting degradation of caribou ecosystems have resulted in a new government policy allowing wolves to be poisoned with Strychnine and shot from helicopters. 12
Some undertaking is so slow one could barely notice. It is not only animals that help clean up dead organisms; fungi play a pivotal role in reducing dying trees to humus and soil, in the mean time providing homes for many. Mycelia, those hairy branching-like hyphae that one sees under a log or inside of a rotting tree, are essential agents of decomposition and dispersing nutrients throughout the ecosystem. Without mushrooms, we wouldn’t survive. Their invasive hyphae and the enzymes they produce (cellulases) are some of the very few agents that are good at breaking down cellulose and lignin fibers, providing energy-rich nutrition for themselves. 8
When a tree begins to die, it may stand for many decades providing nesting holes for birds, food for beetles and grubs, and food for those who eat beetles and grubs. Very few woodpeckers can hammer into solid live wood. Fungus-softened wood is what they need for nesting cavities to raise their young. 9
Tinder polypore (hoof fungus) fomes fomentarius and false tinder mushroom Phellinus igniarius can be seen growing up the sides of old aspen (poplar) trees. Fungi are classified into brown rot or white rot fungi, so named because of the color of the decaying wood. Tinder mushrooms, brown rot fungi, can be used to start fires from sparks; even Ötzi, the Iceman from 3300 BC, was carrying it.
Lawrence Kilham, from Lyme, NH, studied the relationship between yellow-bellied sapsuckers and the fruiting bodies of tinder mushrooms. He found that the birds can hone in on mushrooms growing on trees and are far more likely to excavate nesting holes where they are found. Bernd Heinrich, in his own experiments, confirmed these findings.10
Young sapsuckers are very noisy; possibly ensuring their parents will feed them. This noisiness attracts predators as well; it is important that the nestlings be secure inside their fortress. Heinrich found that aspen nest holes were the safest, made hollow in the inside first by the fungus, then by the bird’s beaks, with a hard shell of sapwood on the outside. Sapsuckers will return to the same aspen trees year after year. They, unlike most woodpeckers do not peck holes looking for ants and grubs; they tap hard surfaces to attract a mate, a sort of sapsucker bird song. For food, they are truly “sap-suckers” making rows of square-like holes in trees, often birches or apples to suck up the sweet sap. Many other animals use sapsucker licks to drink, including hummingbirds, other woodpeckers, nuthatches, kinglets, goldfinch, sparrows, cardinals, squirrels, and many warblers. White-faced hornet queens will also find the licks when first emerging from the spring. 11
Was Lucretius right?
The cycle of life…who are we really? Every living thing on earth and in the air is in a state of being recycled— all the time. Alive or dead, our waste products, dead skin, hair, and feces are recycled into beetles, grass and trees, birds, mammals, and eventually back into us. All bodies are built of carbons linked together; at some point those carbons are disassembled by bacteria, fungi, insects, plants, and animals and released as Co2 into the air. Plants take up carbon dioxide to build their bodies through the help of bacteria and fungi. Who knows where these carbon molecules have come from—a recently dead African elephant, an extinct equisetum from the Carboniferous age, or a dead deer in a nearby field? Carbon dioxide, nitrogen and oxygen (as well as other molecular building blocks of life) are stirred around on the winds and exchanged freely between all of us. Yes, as Lucretius suspected, we truly are one.2
1. Titus Lucretious Carus, 99 BC-55 BC, was a Roman poet and philosopher. His only know work is an epic philosophical poem, De rerum natura written about the philosophy of Epicureanism; it is translated into English as On the Nature of Things.
Translated by William Ellery Leonard
Substance is Eternal
22.214.171.124.7. Heinrich, Bernd. Life Everlasting: the animal way of death. Houghton Mifflin Harcourt, 2012.
6. Audubon, John James. Missouri River Journal 1843
6. Lieberman, Daniel E. The Story of the Human Body: Evolution health and disease. Random House, 2013
6. Flannery, Timothy. The Eternal Frontier: An Ecological History of North America and its Peoples. 2001 Grove Atlantic Press
8. Mooney, Nicholas P. Mushroom. Oxford University Press, 2011.
11. Waltermire, Joan. Holey Alliance. Northern Woodlands. May 26, 2002.
12. National Wildlife Foundation. http://www.nwf.org/news-and-magazines/media-center/news-by-topic/wildlife/2012/02-06-12-tar-sands-development-to-lead-to-poisoning-of-wolves.aspx
Retrieved November 201
- Barred Owl – Micki Colbeck
- Dead deer- Micki Colbeck
- Tinder polypore photos- Micki Colbeck
- Yellow bellied sapsuckers- Mary Holland
- Nicrophorous – en. Wikipedia.org
- Blowfly- flickr.com
- Otzi – http://www.hypertextschool.com
- Yellow-bellied sapsucker and nest hole- Terry Sohl
- Bison- John James Audubon