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Augros & Stanciu's
The New Biology
George Stanciu, PhD, theoretical physics
Robert Augros, PhD, philosophy
Animal and Plant Cooperation
"Nature is not at war, one organism with another. Nature is an alliance founded upon cooperation."
return to "Evolution" main-page
Editor's note: The following is from Augros & Stanciu's The New Biology, chapter four, "Cooperation."
|Robert M. Augros
||George N. Stanciu
Editor's prefatory comment:
One of the marvels of becoming an educated person is to look at an old subject, but now, with new eyes, to see something new; even, a whole new world. What we thought had been settled long ago as irrefutable truth, might suddenly, with more and better information and analysis, be swept away in a moment of profound clarity.
All of our lives, since early science classes in school, we’ve heard that nature is at war with itself; that, there’s blood-stained struggle for existence with only the fittest to survive; that, animals, and plants, too, are locked in a kind of gladiators’ competition, a fight to the bitter death, with only the strongest and most able to win one more day’s existence.
Well, this idea has had a long run. Dear Leaders of world governments, corporations, and churches have adopted this Machiavellian philosophy as the natural way of things, offering them license to prey upon and rule over the weak.
However, there is a problem with the Darwinian paradigm: none of it is true. There is no "dog eat dog," no "law of the jungle." Nature is not at war with itself, all against all; it is not “red in tooth and claw,” as Tennyson so eloquently led us astray.
Below, I’ve offered research data from Augros and Stanciu’s “The New Biology.” It will change the way we look at the world.
After you peruse the following, may I suggest that you survey the “Kairissi and Elenchus” discussion of this topic in the immediately-following article on the “Evolution” main-page.
The paradigm of modern biology depicts nature as a ruthless struggle between opposing forces.
In 1858 Charles Darwin set the tone when, in a paper delivered to the Linnean Society, he made public for the first time his theory of evolution. Darwin opens the paper with a stark image of nature:
“All nature is at war, one organism with another, or with external nature. Seeing the contented face of nature, this may at first be doubted; but reflection will inevitably prove it to be true.”
The co-discoverer of natural selection, Alfred R. Wallace, in a paper presented simultaneously with Darwin’s, employs the same imagery, describing animals and plants as locked in
“a struggle for existence, in which the weakest and least perfectly organized must always succumb.”
Biologist Thomas Huxley, Darwin’s friend and defender, speaks in the same vein:
“The animal world is on about the same level as a gladiator’s show. The strongest, the swiftest and the cunningest live to fight another day… no quarter is given.”
To describe this brutality Tennyson coined the now-famous phrase
“Nature, red in tooth and claw with ravine [violence].”
In The Origin of Species, Darwin maintains that
“all organic beings are exposed to severe competition” and to “the universal struggle for life.”
He argues that this conflict of living things follows inevitably from the tension between limited resources and unlimited population growth.
This paradigm has dominated biology since Darwin’s day. But paradoxically, it does not square with observation.
Ruthless struggle between species can be induced artificially in the laboratory, but it is difficult to point out clear examples of mutual harm between natural species undisturbed by man. Many ecologists and others experienced in field studies of animals candidly admit that the theoretical expectations are not borne out by the observed facts. Daniel Simberloff writes:
“It is rare to see two animals, particularly animals of different species, tugging at the same piece of meat. And even when competition is observed, it often appears inconsequential. Perhaps a fiddler crab scurries into a hole on a beach only to come running out again, expelled by the current inhabitant. But the crab simply moves off to find another hole. Competition between species – interspecific competition – thus appears to be little more than a minor, temporary inconvenience.”
After a three-year study of breeding bird communities in the North American plains and shrubsteppe, John Weins and John Rotenberry discovered that
“variations in the population size of one species in an area are largely independent both of the presence or absence of other species and of variations in habitat features. Coexisting species appear to use resources more or less opportunistically. We find little evidence that they are currently much concerned about competition with one another or that competition in the past has led to an orderly community structure.”
They conclude that
“competition is not the ubiquitous force that many ecologists have believed” it to be.
Weins and Rotenberry began their observations with the conventional assumption that interspecific strife is the central factor in determining how the natural communities are put together. They confess that
“as the research progressed, however, these expectations proved to be naïve.”
Entomologist P.S. Messenger also writes that
“Actual competition is difficult to see in nature.”
Ecologist E.J. Kormondy asserts that competition in natural conditions is rare. And biologists Allee, Emerson, Park, Park, and Schmidt in a collaboratively produced text declare,
“Instances of direct mutual harm between species are not known to us.”
Because of this conflict between the accepted paradigm and what is actually observed in natural communities of species, discussion of competition in biology is fraught with confusion and contradiction.
Evidence that undermines the premises of competitive struggle is presented as the result of competitive struggle. Some claim to see competition operating in the very mechanisms that enable animals to avoid competition. As ecologist Robert Ricklefs says,
“Competition is perhaps the most elusive and controversial of all ecological phenomena.”
The Ways Nature Avoids Competition
A careful review of the many strategies nature employs to prevent competition will bring to light this controversy and help to dispel some of the confusion.
Footnote: Colinvaux points out that “Competition is a word with a clear meaning, valid and hallowed in English usage. There is competition whenever two or more individuals or groups ‘strive together’ (the literal meaning of the Latin roots) for something in short supply. Men compete for prizes, and only one man, or one group of those competing, can win a prize.”
The first and easiest way to prevent two species from harming each other is geographical isolation. Scattered across the globe are many species that could eradicate others in a short time, but this does not happen because they inhabit separate continents… This is why man’s introduction of a species into a region where it does not naturally occur often brings ecological disaster and sometimes the extinction of native species.
But what about organisms in the same habitat? How can similar organisms avoid competing with each other if food and other resources are limited in supply? Similar species avoid competition by dividing the habitat into ecological niches. The presence of one species no more harms another species with a different livelihood than “the practice of a doctor harms the trade of a mechanic living in the same village,” to use a comparison of Lorenz.
Niche means not only the physical space the plant or animal uses, but also how it fits into the community: whether it is a food producer, consumer, or decomposer; how it uses energy sources; what predators and prey it may have; its period of activity; and what changes it makes in the environment.
Among the most thoroughly documented principles in the science of ecology is the dictum that two species never occupy the same niche.
Thousands of examples are known where similar animal species coexist without competing because they eat different foods or are active at different times of otherwise occupy different niches.
Each plant species also occupies a distinct niche: some specialize in sandy soil, others in rich humus; some prefer acid soil, others alkaline; still others require no soil, such as the lichens; some exploit the early growing season, others the late; some get by only because they are tiny, others only because they are huge.
Experiments have shown, for instance, that two species of clover can flourish together in the same field. Of the two species investigated,
“Trifolium repens grows faster and reaches a peak of leaf density sooner. However, Trifolium fragiferum has longer petioles and higher leaves and is able to overtop the faster growing species, especially after T. repens has passed its peak, and thus avoids being shaded out.”
Herbs and grasses have shallow roots to absorb moisture from light rains. Thus they do not compete with trees like oaks that have deep roots to tap more permanent sources deep in the water table. Also, in a deciduous forest many plants bloom and complete their yearly growth before trees have formed enough leaves to shade out the needed sunlight. Other plants require the shade and higher humidity that the forest canopy provides.
Plant physiologist Frits Went writes:
“There is no violent struggle between plants, no warlike mutual killing, but a harmonious development on a share-and-share basis. The cooperative principle is stronger that the competitive one.”
Went exemplifies this principle with the growth of seedlings. Even if several thousand per square yard spring up together they do not kill each other. They simply do not grow to full capacity while sharing the available water, nutrients, and sunlight. He points out that weeds sometimes crowd out desirable garden plants only because the latter have been planted out of season or in the wrong climate. The cooperative principle operates even in harsh environments:
“In the desert, where want and hunger for water are the normal burden of all plants, we find no fierce competition for existence, with the strong crowding out the weak. On the contrary, the available possessions – space, light, water, and food – are shard and shared alike by all. If there is not enough for all to grow tall and strong, then all remain smaller. This factual picture is very different from the time-honored notion that nature’s way is cut-throat competition among individuals.”
The same is true of the jungle:
“The forest giants among the trees do not kill the small fry under them. They hold back their development, and they prevent further germination. In a mountain forest in Java it was observed that the small trees living in the shade of the forest giants had not grown after 40 years, but they were still alive.”
Thus in garden, desert, and forest the paradigm for plants is not competition but peaceful coexistence.
Food specialization is one of the simplest ways that animal species avoid competition. Along the shore of Lake Mweru in Central Africa, three species of yellow weaver birds live side by side without struggle. They do not fight over food since one species eats only hard black seeds, another eats only soft green seeds, and the third only insects.
Many caterpillars will eat only one kind of plant. In some cases the plant’s toxins render it inedible to all but specialist herbivore, as with milkweed and the monarch butterfly larva.
Twenty different insects feed on the North American white pine without competition because five species eat only foliage, three species concentrate on buds, three on twigs, two on wood, two on roots, one on bark, and four on the cambium.
Experiments show that newly hatched, inexperienced garter snakes pursue worm scent by preference over cricket scent. Baby green snakes that live in the same region have just the opposite preference, though clearly both kinds of snake could eat both kinds of prey.
Two species of cormorant found in Britain look very much alike, occupy the same areas of shoreline, and feed and nest in similar ways. The competition paradigm predicts that these animals must be locked in a ruthless struggle, each trying to supplant the other. Close investigation, however, reveals that one eats mostly sand eels and sprats, the other a mixed diet but no sand eels or sprats. One fishes out at sea, the other in shallow estuaries. One nests high on the cliffs or on broad ledges, the other low on the cliffs or on narrow ledges. No struggle. No competition at all. The birds, in fact, occupy different niches.
Size of food is a major factor in determining food preferences. Carnivores, for example, must prey on animals small enough to overpower, but not so small as to be of negligible nourishment for the time and energy invested in the hunt. Man is the only animal not restricted to certain foods by size requirements.
G.D. Carpenter who studied the tsetse fly in the region of Lake Victoria, Africa, found it could suck the blood of mammals and birds whose blood cells vary from 7 to 18 microns in diameter but could not draw blood from the lungfish because its blood cells of 41 microns are too large to pass into the proboscis of the fly.
Sometimes special division of the habitat is sufficient to prevent competition. Five species of cone-shelled, carnivorous snails live segregated from each other in five parallel strips along the shores of Hawaii, where, within each strip, each species attacks with poison darts a unique group of prey.
The niche of many fresh-water fish is circumscribed by their oxygen requirements. Catfish can inhabit the lower, slow-moving regions of a stream where there is little oxygen, but brook trout, which require much more dissolved oxygen, can live only where is aerated by rapids and waterfalls.
[There are also] differing tolerances for salinity in estuarine animals. Thus the clam does not compete with the mussel because it cannot live in the same places.
The space that defines a niche need not be large or far away from others: three different species of mite occupy three different areas of the honey bee’s body as their niches.
Dividing the habitat according to time is another strategy nature uses to prevent competition. Most habitats support two ecological communities, the diurnal and the nocturnal. During the day, bees, butterflies, weasels, most lizards, and most birds are active. At dusk they retire and the night shift takes over, including cockroaches, moths, mice, bats, and owls. Moths feed on white or pale yellow flowers that open only at night, thereby avoiding competition with bees and butterflies.
Ecologist Charles Elton describes the noncompetitive use of the habitat by diurnal and nocturnal animals:
“Not only is one kind of animal replaced by another, but one kind of food-chain is replaced by another, and certain niches which are unused by any animal during the day become occupied at night. The weasel-bank vole industry is changed into a tawny owl-wood mouse industry. The woodpecker-ant connection has no equivalent at night, while the moth-nightjar or bat chain is almost unrepresented by day. In fact, one food-cycle is switched off and another starts up to take its place. With the dawn the whole thing is switched back again.”
Elton offers the unusual example of the gerbille that inhabits the South African veld. This rodent often shares the same underground tunnels with the carnivorous mongoose but is never attacked because
“while the gerbilles come out exclusively at night, leaving their burrows after sunset and returning always before dawn, the mongoose … feed only during the day, and retire to earth at night.”
Biologists Leyhausen and Wolf discovered that with
“domestic cats, living in free open country, several individuals could make use of the same hunting ground without ever coming into conflict, by using it according to a definite timetable … An additional safeguard against undesirable encounters is the scent marks which these animals … deposit at regular intervals wherever they go. These act like railway signals whose aim is to prevent collision between two trains. A cat finding another cat’s signal on it hunting path assesses its age, and if it is very fresh it hesitates, or chooses another path; if it is a few hours old it proceeds calmly on its way.”
Similar species sometimes escape struggling with each other over resources by periodic migration. For example, the white storks and the black storks that winter in Africa spend the rest of the year in Europe. They
“thus have avoided competition with their tropical relatives, not by radiating into unique food niches but by leaving the area,”
says zoologist M. Philip Kahl. Other animals that migrate – some as far as 12,000 miles – include caribou, bats, whales, birds, dragonflies, butterflies, fish, eels, and turtles.
The migration strategy is not open to plants, of course. Flowering plants avoid interspecific competition for pollinators by flowering sequentially, each species in its turn, as commonly occurs in the Arctic, the temperate zones, and in the tropics. To these differences of timing correspond the active periods of pollinators such as bats, hummingbirds, and insects.
Ricklefs points out that of the four species of honey bee that occur in England, Bombus pratorum coexists peacefully with Bombus agrorum because the former is active earlier in the season. The other two species do not fight over the same flowers because they restrict themselves to woods rather than open fields, and B. hororum has a much longer tongue, so it feeds only at flowers with long corollas that the other three short-tongued species do not visit.
In a similar way, miconia trees of several species … fruit at different times, thereby avoiding competition for birds to eat the fruit and scatter the seeds.
But how can different grass species, living blade against blade in the same turf, using the same water and nutrients, avoid competition? There would seem to be no room for a division into different niches. The answer is the cropping principle, described [even] by Darwin:
“If turf which has long been mown, and the case would be the same with turf closely browsed by quadrupeds, be let to grow, the more vigorous plants gradually kill the less vigorous, though fully grown plants; thus out of 20 species growing on a little plot of mown turf (3 feet by 4) 9 species perished, from the other species being allowed to grow up freely.”
Stated the other way around, constant browsing allowed 9 more species of grasses to thrive than would otherwise be possible. Here the browser eating the grasses prevents the competitive elimination of some species from the turf. Herbivores also have their preferences, and this leads to a kind of cooperation. In a mountain meadow, goats will keep down the population of the plants they like best to eat. This gives other plants more chance to grow.
These other species may be preferred by an elk or a big horn sheep, leading to a rich variety of plant species and food for all without competition. Part of a niche of a grass species in a meadow is being inedible or at least unpalatable to all but a particular herbivore; the plant accomplishes this by growing thorns or by producing special toxins such as nicotine, digitalis, or hypercin.
As a general rule, the larger the mammal herbivore, the longer the list of plant species it eats, taking only a little of each one to minimize the effects of toxins and at the same time producing a balanced crop.
The herbivores also have special habits and equipment that preclude fighting over the same foods. Colinvaux explains how three browsers coexist on the African savanna:
“Zebras take the long dry stems of grasses, an action for which their horsy incisor teeth are nicely suited. Wildebeest take the side-shoot of grasses, gathering with their tongues in the bovine way and tearing off the food against their single set of incisors. Thompson’s gazelles graze where others have been before, picking out ground-hugging plants and other tidbits that the feeding methods of the others have both overlooked and left in view. Although these and other big-game animals wander over the same patches of country, they clearly avoid competition by specializing in the kinds of food energy they take.”
The zebra, the wildebeest, and the gazelle in their turn are the common prey of 5 carnivores: the lion, the leopard, the cheetah, the hyena, and the wild dog. These predators can coexist because there are
“5 different ways which do not directly compete to make a living off 3 prey species,”
according to ethologist James Gould. He explains:
“Carnivores avoid competition by hunting primarily in different places at different times, and by using different techniques to capture different segments of the prey population. Cheetahs are unique in their high-speed chase strategy, but as a consequence must specialize in small gazelle. Only the leopard uses an ambush strategy, which seems to play no favorites in the prey it chooses. Hyenas and wild dogs are similar, but hunt at different times. And the lion exploits the brute-force niches, depending alternatively on short, powerful rushes and strong-arm robbery.”
And these 5 predators are far from significantly reducing the 3 prey species…
The elimination of competition by division of the habitat into niches is so universal in the plant and animal kingdoms that it has become a principle of prediction and discovery for field studies.
“Whenever we find rather similar animals living together in the wild, we do not think of competition by tooth and claw, we ask ourselves, instead, how competition is avoided. When we find many animals apparently sharing a food supply, we do not talk of struggles for survival; we watch to see by what trick the animals manage to be peaceful in their coexistence.”
In a classic study, ecologist Robert MacArthur set out to learn how 5 species of warbler, similar in size, shape, and diet, could live together in the same coniferous forest in Maine. What factor was
“preventing all but one from being exterminated by competition”?
After months of painstaking observations, MacArthur discovered that each species had defined a subtle niche for itself based mainly on behavior:
“The birds behave in such a way as to be exposed to different kinds of food. They feed in different positions, indulge in hawking and hovering to different extents, move in different directions through the trees, vary from active to sluggish, and probably have the greatest need for food at different times corresponding to the different nesting dates. All of these differences are statistical, however; any two species show some overlapping in all these activities.”
“Derived from a classic study by ecologist Robert MacArthur, this diagram illustrates how five species of warbler, similar in size and shape, feed on bud worms in the same spruce trees. They avoid competition by occupying subtly different niches. The shaded areas indicate where each species spends more than half its time. The birds also use different methods of hunting. This pattern of noncompetition is typical of naturally coexisting species.”
Colinvaux concludes that
“Nature is arranged so that competitive struggles are avoided,”
and adds that
“peaceful coexistence, not struggle, is the rule.”
Where food and other necessities are abundantly available many species may coexist in the same area without conflict.
Herbert Ross found that 6 species of leafhopper in Illinois thrive side by side on the same trees without competition. Such aggregations of similar species are called guilds. Hundreds of cases are known of large numbers of similar species coexisting without interference. An investigation of 14 species of coexisting hummingbirds revealed that the birds feed differently according to flower density, height of flowers, and the time of nectar renewal, with small overlap between species.
In the same forest log there are diverse niches for 7 species of millipede. Ricklefs reports that
“The shallow waters of Florida’s Gulf Coast can harbor up to 8 species of large predatory snails … Lake Malawi in Africa has more than 200 species of cichlid fish, which appear to have similar ecological characteristics.”
Nature engages all her ingenuity in developing techniques to forestall strife among species.
It is not surprising, then, that even careful and experienced investigators trying to document the paradigm of competition come up with disappointing results. Andrewartha and Birch comment on David Lack’s paper
“Competition for Food by Birds of Prey”: “We have discussed Lack’s studies of birds in some detail because this work is so well documented. But we are forced to conclude that his interesting results do not in any way demonstrate that ‘competition’ between birds in nature is at all commonplace or usual. On the contrary, his results seem to show that it hardly ever occurs. Where he finds species together, there is evidence that their food is ‘superabundant,’ or else they live on different foods. When they are separated, they is no evidence that they do invade one another’s territories.”
Because each species has its own niche and its own task, fights between animals of different species are exceedingly rare, if they occur at all.
Lorenz after many years of studying fish remarks,
“Never have I seen fish of two different species attacking each other, even if both are highly aggressive by nature.”
Lions often steal the kills of cheetahs, but there is never a struggle. The cheetah, much too wise to take on an opponent more than double its weight, abandons its prey without a fight.
The same prudent retreat occurs if a monarch eagle intrudes on a smaller eagle’s meal of carrion, for instance. The smaller bird withdraws without protest and waits until the monarch eats its fill. As mentioned above, Allee and his collaborators did not know of any
“direct mutual harm between species.”
Colinvaux puts it succinctly:
“A fit animal is not [defined as] one that fights well, but one that avoids fighting altogether.”
Predation is best understood not as a struggle but rather as a kind of balanced coexistence. In natural populations predators do not exterminate prey species.
As a particular prey animal becomes more scarce, the predator turns to more abundant substitutes.
The wolf does not compete with the caribou but depends on it. The caribou does not struggle with the lichens it consumes but depends on them for its livelihood. It is in the predator’s interest that the prey thrive. Andrewartha and Birch state flatly,
“There is no competition between the predator and its prey.”
Odum notes that
“where parasites and predators have long been associated with their respective hosts and prey, the effect is moderate, neutral, or even beneficial from the long term view.”
Predation does not benefit the individual that is eaten, but it can benefit the rest of the prey population in several ways. After a three-year study of the wolf population in Isle Royale, an island in Lake Superior, L. David Mech writes:
“The wolves appear to have kept the moose within its food supply, culled out undesirable individuals, and stimulated reproduction. Wolves and moose probably will remain in dynamic equilibrium.”
After a similar study of the wolves of Mount McKinley National Park in Alaska, Adolph Murie states of the Dall’s sheep indigenous to the area:
“Wolf predation probably has a salutary effect on the sheep as a species. At the present time it appears that the sheep and wolves may be in equilibrium.”
One benefit of predation is that in certain cases more diversity in prey species is allowed than would otherwise obtain because competitive exclusion is prevented. The addition of a single predator can increase the number of prey species that can live side by side in a given habitat. For example, David Kirk writes:
“One of the most important effects of predator-prey interactions is the reduction of competition between prey species that share a common predator. For example, the sea star Pisaster is a major predator on sedentary mollusks and barnacles of the intertidal zone. If the sea star is excluded from the community, one or two of the sedentary species soon crowd or starve out the other sedentary species because of their competitive advantage in feeding and reproduction. However, if the sea star is allowed access to the simplified community, it removes many individuals in these successful sedentary populations, leaving space for immigration of individuals of several other species. In other words, the addition of a single predator species can lead to an increase in the total number of prey species.”
L.B. Slobodkin has obtained similar results with different species of hydra in laboratory cultures. In the same way different insects preying on specific seeds and seedlings prevent or reduce tree competition.
The predator is not the enemy of its prey in the sense of hating or being angry with it.
Lorenz clarifies the relation:
“The fight between predator and prey is not a fight in the real sense of the world: the stroke of the paw with which a lion kills his prey may resemble the movements that he makes when he strikes his rival, just as a shotgun and a rifle resemble each other outwardly; but the inner motives of the hunter are basically different from those of the fighter. The buffalo which the lion fells provokes his aggression as little as the appetizing turkey which I have just seen hanging in the larder provokes mine. The differences in these inner drives can clearly be seen in the expression movements of the animal: a dog about to catch a hunted rabbit has the same kind of excitedly happy expression as he has when he greets his master or awaits some longed-for treat. From many excellent photographs it can be seen that the lion, in the dramatic moment before he springs, is in no way angry.”
Even the unavoidable struggle is minimized.
Mech reports that 51 moose kills he examined were composed of the very young, the old, and the diseased. None of the animals killed by the wolves was in its prime. A wolf pack sensibly seeks out prey that will offer the least fight. Murie found the same thing with wolf predation of Dall’s sheep. Finally,
Predators do not practice wanton killing, even the pain seems to be minimized.
Rodents attacked by snakes commonly go into shock before being killed and devoured. A wildebeest surrounded by attacking lions does not even resist but falls into shock.
The same principles hold regarding the parasites found universally among animals and plants. Authorities agree that parasitism is rarely harmful to the host.
“It is the exceptional parasite that is deleterious,”
writes Thomas Cheng. For example,
“The Okapi, which lives in the tropical forests of central Africa, harbours at least 5 kinds of worms simultaneously and some of these may be present in numbers of several hundreds; the host does not seem any the worse for this and can feed itself as well as cater for the fauna it contains,”
according to parasitologist Jean G. Baer. Some parasites have intricate life cycles requiring one or more secondary hosts. The larvae of the brain worm that parasitizes the white-tailed deer live in slugs and snails that the deer inadvertently ingest when grazing. The larvae then penetrate the deer’s stomach and enter the spinal column, eventually migrating to the space surrounding the brain. Here they mate and lay eggs that pass via the bloodstream to the deer’s lungs where they are coughed up, swallowed, and passed out with fecal waste to reinfect another snail. But the damage to the host animal is minimal. Ecologist Robert L. Smith remarks,
“As with most parasites and hosts, the deer and the brain worm have achieved a mutual tolerance, and the deer does not suffer greatly from the infection.”
The host’s continued health and well-being are clearly in the interest of the parasite. This is why, as Cheng observes,
“recent evaluations of the host-parasite relationship have intentionally avoided employing ‘the infliction of harm’ as a criterion in distinguishing parasitism from other categories of symbiosis.”
Harm results only when parasites are present in excessive numbers. In fact, several controlled experiments have proven that certain parasites enhance growth and vigor of the host, either by providing nutrients or by modifying the host’s metabolism.
Competition can be induced between species artificially in the laboratory. But the experiments of Gause and others prove that such competition cannot persist with stability. Either the two species find subtly different niches and thereby avoid competition or one species replaces the other. This confirms the one species, one niche principle found in nature.
Mathematical models, laboratory experiments, and field studies all show that competition between species cannot be sustained.
The competition between paramecia in an aquarium, or between flour beetles in a jar is unnatural since migration, the natural means of avoiding competition, is prevented.
Furthermore, those laboratory experiments imply that
If all nature were at war, one organism with another, then only one species would survive. If life is not to destroy itself, competition must be avoided. Thus competition is not the paradigm.
Competition between Species
A recognition of the peaceful coexistence among animals and plants is only half the story. The Darwinian images of struggle and war have led biologists to seek competition everywhere and to overlook or downplay cooperation.
Biologist William Hamilton writes,
“Cooperation per se has received little attention from biologists.”
Zoologist Robert M. May notes that
“mutualism has remained relatively neglected – in field, laboratory, theory and textbooks.”
And Lynn Margulis writes,
“Although they are often treated in the biological literature as exotic, symbiotic relationships abound; many of them affect entire ecosystem.”
Nature’s manner is not merely peaceful coexistence, but cooperation.
“It is doubtful whether there is an animal alive that does not have a symbiotic relationship with at least one other life form.”
A few examples will give some idea of the magnitude of this mutual interdependence among living things. One organism can be helpful to another in several ways: by providing food, protection from predators, a place to live, or transportation, or by ridding other organism of pests, or by preparing some necessary condition for its life or welfare. The innumerable cooperative associations between different species constitute one of the most intriguing subject areas in all natural science. The variety and subtlety of interdependence is astounding.
The simplest service one organism can offer another is providing a place to stay. The sea worm Urechis caupo is nicknamed “the innkeeper” because it regularly harbors various fish, mollusks, arthropods, and annelids – up to 13 species – in the U-shaped burrow it makes in California’s coastal mudflats. Though able to live independently, the lodgers reside on whatever Urechis brings in but does not consume.
Certain crabs live within the rectum of sea urchins, others within the shells of live oysters. The horseshoe crab is also host to many guests. Clarke notes:
“Anyone who has an opportunity to catch an elderly horseshoe crab (Limulus polyphemus) in the shallow waters off the New England coast is likely to find several species of mollusks, barnacles, and tube worms attached to the shell and a number of more motile commensals living in the ‘book gills’ or anatomical nooks of this strange animal.”
In fact, any sea animal with a shell or available space of any sort will serve as home for other species. Farb adds that
“the porous body of a sponge provides a home for a wide variety of sea creatures. One large specimen found growing off the Florida Keys served as habitation of 13,500 animals – some 12,000 of these were small shrimps, but the other 1,500 included 18 different species of worms, copepods, and even a small fish.”
Plants called epiphytes use other, established plants for a place to live. Tropical orchids, mosses, bromeliads, and vines grow along the horizontal branches of trees or hang down from them. These epiphytes are thus able to find a place in the sun and yet do have to make the enormous investment in growing tall support structures.
It would be impossible to list all the animals that use plants for shelter and breeding. But some animals have formed close mutual relationships with certain plant species. Kirk writes of the Acacia of Central America:
“Ants of the genus Pseudomyrmex live in the swollen thorns of the plant, gain their sugar from nectarines on the leaves, feed their larvae with modified leaflet tips that are rich in proteins and steroids, and have a nearly continuous food supply because these species of Acacia remain green during the dry season … The ants, in turn, drive away plant-eating insects and prune back vines and shrubbery that might crowd out the Acacia. This activity is of immediate benefit to the ants because it keeps the Acacia strong and healthy and ensures a more continuous and abundant food supply. The larger the ant colony, the effective the continuous protection that it provides for the plant; thus, both ants and Acacia can maximize their growth through this close mutualism.”
Many other trees, shrubs, and plants carry on cooperative associations with ants. The aspen sunflower of the Rocky Mountain area secretes extrafloral nectar rich in sugar and containing 18 different amino acids needed for ant nutrition. Ants feed on the nectar and protect the flower’s seeds from devastating parasites…
Many animals use the help of other species to obtain food. The blue jay can open acorns, but the bobwhite cannot. The blue jay is a sloppy eater, however, and leaves much meat uneaten in the opened shells. The bobwhite then feeds on a source it could not exploit itself.
Eating the leavings of others is a widely exploited niche in every ecosystem. Hyenas frequently scavenge from lion kills… The Arctic fox lives largely on the remains of kills made by polar bears…
Another service one species can perform for another is to provide transport, either of the whole organism or of its seeds… The mantle of one fresh-water mussel, Lampsilis ventricosa, is modified to look like a small fish. Clark writes:
“When a real fish, attracted by this mimic, swims over the mussel, casting a shadow, the mussel discharges its glochidial larvae. Some of these larvae reach the gills or fins of the fish to which they attach and live as parasites until they are ready to metamorphose into adults. Certain fishes thus parasitized wander upstream where the young mussels drop off and begin a new life as independent bottom animals. In this way these sessile form are distributed against the current to the upper reaches of the stream.”
Barnacles attached to whales and anemones attached to crabs get free transport and an opportunity to obtain food otherwise unavailable. The anemones also provide the crabs with camouflage and probably prevent predation by octopus.
There are hundreds of insects and worms that use other organisms for transportation and dispersal to more promising habitats. This practice of hitchhiking, called phoresis, has been going on for at least 25 million years, as if proven by amber fossils of various mites and nematodes clinging to beetles and wasps.
Flowering plants use bees, moths, hummingbirds, and bats to achieve cross-fertilization, rewarding the workers with nutritious nectar. Many of these associations have developed into obligatory mutualism between plant and animal, so that they allow prediction…
Fruits are another way plants disperse their seeds with the aid of animals. The animal eats the fruit and, sometime later and some distance away, excretes the undigested seeds, which are thus provided with their own supply of rich fertilizer…
Various algae form symbiotic partnerships with a wide range of animals… Algae form intimate symbiotic relationships with many fungi, producing what amounts to a new organism, the lichen, that can grow under conditions where neither the alga nor the fungus alone could survive…
Another plant-plant partnership is that of the mycorrihizal fungi that lives in association with the roots of most forest trees… Odum explains the relationship:
“Many trees will not grow without the mycorrihazae…”
Another service is provided to certain plants by nitrogen-fixing bacteria. These microbes take up residence within the roots of legumes…
Other bacteria and protozoans have developed a mutualism with hundreds of mammalian herbivore species… The domestic cow, for example, does not have the enzymes necessary to digest cellulose…
A further service one organism renders another is protection…
Many species take warning of danger from other species…
Another service one animal can offer another is cleaning…
In another form of interdependence, certain large animals support whole communities of species. A single hippopotamus … is cleaned by 20 or so labeo fish and stirs up food for other fish as it walks along the water…
The exquisite cooperation between plants and animals … is a marvel in itself. Plants use the carbon dioxide in the air and water from the soil to manufacture sugars, releasing oxygen as a by-product… Without this perfect cycle, life on the earth would have gone out of business long ago… Burkholder writes:
“All organisms are dependent upon the varied activities of other organisms for the supplies of essential stuffs.”
No single species could persist if it were alone on the planet.
Lynn Margulis writes:
“All organisms are dependent on others for the completion of their life cycles. Never, even in spaces as small as a cubic meter, is a living community of organisms restricted to members of only a single species…”
The recognition of such universal, essential cooperation among animals and plants alters the conventional image of nature.
Biologist Lewis Thomas writes:
“One major question needing to be examined is the general attitude of nature. A century ago there was a consensus about this; nature was ‘red in tooth and claw,’ evolution was a record of open warfare among competing species, the fittest were the strongest aggressors, and so forth. Now it begins to look different… The urge to form partnerships, to link up in collaborative arrangements, is perhaps the oldest, strongest, and most fundamental force in nature. There are no solitary, free-living creatures, every form of life is dependent on other forms.”
Cooperation within Species
Cooperation is also the ruling principle among members of the same species, despite Darwin’s assertion that
“The struggle will almost invariably be most severe between the individuals of the same species, for they frequent the same districts, require the same food, and are exposed to the same dangers.”
How can members of the same species avoid competition if they all occupy the same niche? Nature is not at a loss for methods.
One way is to have some technique to separate individuals from each other. This is accomplished in animals and plants by various dispersal techniques. Tinbergen explains:
“These ‘dispersion mechanisms’ reduce competition to a minimum. Perhaps the simplest way to disperse is just to drift aimlessly about for a while, carried and scattered by the wind or water until the time for settling has arrived…”
Every living thing has a dispersal phase at some stage in its life cycle…
[The most prevalent form of ‘dispersion mechanism’ is the use of territories, which is far more common than we’ve known.] Animals that mark off and defend definite areas divide their niche into livable plots. Territories, for mating or feeding, or both, are established by hundreds of species including limpets, lobsters, crabs, spiders, crickets, grasshoppers, many other insects, bony fishes, lizards, perching birds, raptors, oceanic birds, rodents, ruminants, and most other mammals. The power of territorial borders is surprising.
Zoologist Hans Kruuk has seen hyenas break off the chase of a promising prey animal when they reach the border of a neighboring hyena territory, even though no other predators are in sight. His field studies showed that
“Fully 20% of unsuccessful wildebeest hunts could be attributed to hyena respect for one another’s boundaries.”
“Territorial behavior leads to an optimum distribution of limited resources among a maximum number of individual species.”
For example, territory size appears to be regulated by innate factors. Song sparrows never establish territories greater than one acre, no matter how few are present. Nor do they defend territories below half an acre, no matter how many other sparrows are present.
A study of 400 coexisting howler monkeys in Central America revealed 23 different clans with definite territories.
The defense of territory in all species is characterized not by battles to the death, but by highly stereotypical threats, aggressive displays, and appeasement gestures that rarely result in injury.
Lorenz observes that these ritualized sign stimuli are as powerful as the impulses of hunger, sex, and fear in the animal. The encounter is more a ritualized contest than a real fight, with one animal eventually retreating unharmed. Territory boundaries tend to be respected.
Footnote: Intraspecies encounters between rival animals rarely result in injury because they are regulated by instinctual, stylized displays of aggression and by appeasement gestures. A wolf, for example, that feels it is no match for another wolf during an encounter avoids a fight simply by presenting its unprotected throat to the adversary. This stimulus never provokes attack by the other wolf. On the contrary, it causes the dominant animal to turn away, and the tension of the encounter is dissipated.
“Particularly when the territory is well established, the defender is usually successful in driving away an invader irrespective of differences in size, strength, development of specialized structures important in the aggressive display, and so forth. This is most clearly seen in the case of two individuals with adjacent territories. Here, each individual is usually successful in defending its own territory yet unsuccessful in attempts to encroach on its neighbor’s domain. In every interaction each individual appears to be driven by opposing tendencies: fight and flight. The closer to the center of its own territory an individual is, the greater appears to be its motivation to fight. But the farther it is from the center of its home territory, the greater appears to be the tendency for flight.”
This system can hardly be described as a brutal struggle or ruthless warfare if size and strength do not determine the outcome.
Zoologist Norman Owen-Smith notes:
“Territoriality of the white rhinoceros may thus be described as a system for ordering specifically reproductive competition among males. Its primary function within the population seems to be to increase the reproductive efficiency of prime bulls by reducing the incidence of injury-inflicting combat. These statements can probably be broadened in scope to apply, with the exception of the Indian rhino, to all other ungulates in which territoriality has been identified, and perhaps to any species in which territoriality is restricted to adult males.”
Some species maintain non-competitive distribution without even encountering each other. Certain mammals accomplish this by leaving scent marks in their territory that other members of the same species avoid. The male frogs of certain species distribute themselves evenly throughout the habitat by distancing themselves from the croaking of other males.
Plants avoid competition with their own seeds by many dispersal techniques. A single crop spread over acres and acres of land is found only in man’s artificial agriculture, never in nature.
Another means nature uses to prevent competition and fighting among gregarious animals is the dominance hierarchy, which minimizes aggression within the social group.
First studied among pecking orders among birds, the dominance hierarchy prevents animals of the same group from wasting time and energy by constantly fighting over food and mates. Instead of fighting, the individual animal lower in the pecking order immediately concedes to the higher one, without any struggle.
Kirk gives an illustration of what happens without this strategy:
“For the group, dominance assures stability. Once hierarchical order has been established, aggression over resources and mates is kept to a minimum. In one study, the investigator deliberately kept disrupting the dominance relationships in a flock of hens. The outcome was that the hens fought more, ate less, gained less weight, and suffered more serious injuries than the control flock in which the dominance relationship was stable.”
Among Japanese macaques of Koshima Island, dominant males break up quarrels between females that have no dominance hierarchy of their own. Dominance hierarchies, found in many species of birds and mammals, show nature to be not only pacific but sensible. Why should a weaker individual fight a stronger one that would win anyway with probable injury to both?
On rare occasions injury results from territory defense or rival encounters, but the aim of aggression is never the extermination of the fellow members of the same species. If it were, a species would destroy itself in a short time.
Fights to the death and cannibalism do sometimes occur in unnatural circumstances, such as birds in a cage, or fish in an aquarium, where retreat is impossible. But such is not nature’s way. Animals with the most dangerous weapons also have the strongest instincts to prevent their use against a conspecific [“a member of the same species”]. Male giraffes that can dispense a lion with a single kick save their lethal hoofs for predators only, using their stubby, harmless horns for encounters with rival giraffes.
Lorenz points out:
“Those inhibitions which prevent animals from injuring or even killing fellow members of the species have to be strongest and most reliable, first in those species which being hunters of large prey possess lethal weapons which could as easily kill a conspecific; and secondly, in those species which live gregariously.”
After a study of dominance in bison herds, ethologist Dale F. Lott concludes:
“Because fighting is dangerous and demands so much time and energy, substitutes have developed. In animals that establish – and defend – territories … fighting is often avoiding because individuals are separated by distance. But species whose social life is organized by dominance depend heavily upon the ability to predict each other’s behavior from such signals as postures and vocalizations.”
An ecological niche can also be divided by learned behavioral differences within a species. For example, one species of oyster catcher [birds] found along English shores is divided into two behavioral groups, the “stabbers” and the “hammerers,” each of which mates only with its own kind. Stabbers feed on mussels and cockels that remain under water in tidal pools at low tide. Such mussels leave their shells partially open to continue filtering food from the sea water. The bird thrusts its beak into the shell, cuts the abductor muscle, and opens the shell to eat the contents. Hammerers feed on mussels and cockels that remain closed at low tide by persistently beating on a vulnerable spot on the shells until the beak can be inserted to pry the shell open. In this way two groups within the same species live in the same area and eat the same foods, but, because of their different hunting techniques, they do not compete.
Within a species, we take for granted the profound cooperation of the family, the herd, the colony, the flock, and the school.
But these are also founded on strong natural instincts. Lorenz speaks of the powerful inhibitions in male wolves, lizards, hamsters, gold finches, and many other species against biting females. He adds:
“The fact that mothers of brood-tending species do not attack their young is thus in no way a self-evident law, but has to be ensured in every single species by a special inhibition … Every livestock breeder knows that apparently slight disturbances can cause the failure of an inhibition mechanism of this kind. I know of a case where an airplane, flying low over a silver-fox farm, caused all the mother vixens to eat their young.”
There are many advantages of flocking together. Many eyes are better than a simple pair in looking for predators, and a circle of musk oxen is more formidable to a wolf pack than is a single animal.
Moving in schools and flocks also makes it difficult for a predator to single out one individual when dozens of others cross its field of vision… A certain population density is necessary for many animals: muskrats, for example, do not breed successfully below a density of one pair per mile of stream or 86 acres of marshland. Many sea birds hunt in flocks because it is more efficient. All social insects live by cooperation. The individuals in a termite colony depend on each other absolutely, some being unable to feed themselves and other being unable to reproduce. Parental care, feeding, protection, and training of young is simply too extensive to summarize. We may point out, however, that for those species that reproduce sexually, at least some kind of cooperation between the sexes is unavoidable.
After years of studying group life among animals, Allee declares:
“No free animal is solitary through its life history.”
Having reviewed the extent of cooperation between species and within a species, we can now reexamine Darwin’s reason for proposing competition as the paradigm for living things. He maintains that,
“a struggle for existence inevitably follows from the high rate at which all organic beings tend to increase.”
Darwin begins by assuming that each living thing is trying to produce an unlimited number of offspring:
“Every single organic being may be said to be striving to the utmost to increase its numbers.”
“There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair.”
He offers the example of the elephant to illustrate the point:
“The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase; it will be safest to assume that it begins breeding when 30 years old, and goes on breeding till 90 years old, bringing forth 6 young in the interval, and surviving till 100 years old; if this be so, after a period of from 740 to 750 years there would be nearly 19 million elephants alive, descended from the first pair.”
If, in fact, the earth is not swamped with elephants or any other species, there must be some check to their geometric growth rate. So he concludes:
“Each species, even where it most abounds, is constantly suffering enormous destruction at some period of its life.”
Darwin proposes four causes that check a species’ natural tendency to increase without limit: predation, starvation, severities of climate, and disease. In a word – death.
Lacking detailed field studies of natural populations – they were done 100 years later – Darwin buttresses this argument based on “mere theoretical calculations” with examples of domestic animals “run wild,” in other words, from man’s artificial introduction of a species into a habitat where it did not occur before.
Recent field studies of native animals by ecologists have yielded conclusions quite different from Darwin’s.
Elton and Andrewartha and Birch argue that starvation rarely acts as a direct influence on numbers of species. Lack says the same of disease. What, then, are the factors?
Take Darwin’s examples of elephants. Laws reports that a study … of over 3000 elephants … showed that
“the age of sexual maturity in elephants was very plastic and was deferred in unfavorable situations … Individual animals were reaching maturity from 8 to 30 years.”
The same study showed that the females do not continue bearing young until 90, as Darwin thought, but stop becoming pregnant around age 55. Thus the elephant population is regulated not by predation, starvation, or death, but by adjustments in the onset of maturity in females, which lowers the birth rate whenever overcrowding occurs.
Nor are elephants unique in having an internal mechanism for regulating population growth. Evidence from other field studies indicates that the birth rate or the age of first reproduction depends on population density in many large mammals, including white-tailed deer, elk, bison, moose, bighorn sheep, Dall’s sheep, ibex, wildebeest, Himalayan tahr, hippopotamus, lion, bear, dugong, harp seals, southern elephant seal, spotted porpoise, striped dolphin, blue whale, and sperm whale.
Increases in population density alter birth rates in small mammals also. Kirk observes:
“In experiments with rats, mice, and voles, definite psychological changes accompanied increase in population density … [which] led to an increase in the weight of adrenal glands and a decrease in the weight of thymus and reproductive glands. The degree of the effect was inversely related to social rank. Dominant individuals were affected little if at all; subordinates were strongly affected. These changes were accompanied by decreases in reproduction.”
Under crowded conditions, female mice ovulate more slowly or stop ovulation altogether. In some species of birds, failure to gain a territory prevents the onset of sexual maturity.
In many animals, then,
Population growth is regulated by benign internal causes without any need for the periodic devastations Darwin supposed.
Another fault in Darwin’s argument is the assumption that
“amongst animals there are very few which do not annually pair.”
On the contrary, a large nonbreeding portion of the adult population is the norm in many species.
In a five-year study of nearly 200 white rhinoceros … Norman Owen-Smith found that only two-thirds of the adult population maintain territories, allowing subordinate males to graze in their territory but not allowing them to breed.
Many bird species keep a reserve of nonbreeders in the population. This was discovered accidentally in a study of the spruce bud worm and its predators. Experimenters … attempted to [remove] the birds from a 40 acre tract ... The number of territorial males before the [removal] took place was 148. [The experimenters removed] and collected 302 males from the area, however, in less than a month. They write:
“For most species, over twice as many adult males were collected on the area as were present before the collecting started.”
The explanation was a large surplus population of unmated males that quickly filled in vacated territories. The replacement of removed birds does not demonstrate competition but is a safety device to regulate population…
We may infer from these experiments that predation would not significantly affect the population growth rate…
According to Ricklefs,
“Detailed removal-replacement experiments have had similar results, indicating that territorial limitation of breeding population is quite general.”
This includes field studies on blackbirds, red grouse, voles, dragonflies, and pomacentrid fish. Not taking these facts into account, any argument for geometric increase in natural populations is based on “mere theoretical calculation,” which, though mathematically correct, are biologically irrelevant.
It is also erroneous to assume that those adults that do mate produce the same number of offspring each season.
A wide range of animals vary their litter size and clutch size according to the amount of food available. Elton observes:
“The short-eared owl … may have twice as many young in a brood, and twice as many broods as usual, during a vole plague when its food is extremely plentiful.”
Lack points out that nutcrackers normally lay only three eggs but increase the clutch to four eggs when there is a bumper crop of hazelnuts. He also mentions that the arctic fox is known to produce much larger litters when lemmings are abundant, and that lions bear more or fewer cubs per litter according to the availability of food. By contrast, in lean years many species do not breed at all.
In some cases the herbivore population is controlled by the plant. For example, in years following a drought, sagebrush develops high concentrations of phytoestrogens that mimic reproductive hormones in the California quail. These hormones inhibit ovulation in the quail that consume the sagebrush, causing a sharp drop in the size of the quail population. When rainfall becomes more plentiful, the sagebrush has little or no phytoestrogen mimics, and quail populations return to normal. Here the herb imposes birth control on the herbivore. Studies show also that ovarian activity is shut down in the mountain voles in the late summer because of phytoestrogen buildup in the grasses they consume.
Also false is the assumption that animals and plants produce as many eggs and seeds as physiologically possible.
All bird species have a normal clutch size, but if the eggs are removed, the female can be induced to lay many more. The domestic fowl, if left all its eggs, produces a clutch of about 12, but if the eggs are removed daily, it can lay up to 360 per year…
[The normal number of eggs varies from species to species.] The general rule is that the number of eggs is inversely proportional to parental care and protection. The female mackerel, which offers no care to its young, lays 2 to 3 million eggs, 99.9996 percent of which are eaten by predators within 70 days, leaving only 2 or 3 individuals that reach adulthood. The sea catfish, on the other hand, lays only 30 eggs per season; almost all survive because the male protects them in his mouth.
Producing enormous numbers of offspring is not proof of ruthless competition but rather of cooperation since the excess of eggs and seeds support thousands of predators that could not otherwise subsist.
If all species used the high-care, low-fecundity strategy, the vast numbers of and varieties of animals we see in nature would not be possible.
And this is not accomplished at the price of annihilating the prey species. There are still millions of mackerel in the sea every year.
No species strives to increase without limit, any more than an individual tends to grow to infinity. And
Animal populations are limited not by struggle, starvation, and death, but by restricting the number of breeders in various ways and by varying the number of offspring produced at a time by each female.
Biologist V.C. Wynn-Edwards comments on Darwin’s assumption that every living thing strives to increase its numbers geometrically:
“This intuitive assumption of a universal resurgent pressure from within held down by hostile forces from without has dominated the thinking of biologists on matters of population regulation, and on the nature of the struggle for existence, right down to the present day. Setting all preconceptions aside, however, and returning to a detached assessment of the facts revealed by modern observation and experiment, it becomes almost immediately evident that a very large part of the regulation of numbers depends not on Darwin’s hostile forces but on the initiative taken by the animals themselves; that is to say, to an important extent, it is an intrinsic phenomenon.”
That populations are self-regulating fits well with the notion of life as directed self-improvement.
Nature is not at war, one organism with another. Nature is an alliance founded upon cooperation.
Editor's last word:
"Animals fulfill God's will most faithfully: they live to fulfill their Creator's purpose. We do not do this. We meddle with the work of the Creator. But the animals are themselves, and they fulfill the will of God that is within them in a true and faithful manner." Carl Jung