4. The Voyageof the Animals

Green turtles are seagoing monsters weighing up to a quarter of a ton, who boast ancestors that swam, perhaps, in Permian seas 200 million years ago, who survived somehow the fall of the great reptiles nearly 100 million years ago, yet whose heroic qualities until about five years ago had been recognized by none but cooks. Then a few stubborn scientists, heroes themselves as we shall see, began to wonder how green turtles find their way home.

In my last chapter we inspected those mysterious commands of both energy and responsibility which the home-place directs to the possessor. They are commands mediating with impartial calm the affairs of men and other animals. Now, however, we turn to a force equally mysterious, equally, it would seem, beyond our present powers of explanation, which so far as we know does not animate our kind. We human beings may have our nostalgias. My thoughts may wing like the sooty tern toward the place where I was born. But unlike so many of my animal fellows, I lack the innate power to find it. Man is one species brilliantly equipped by nature to get himself hopelessly lost.

We may lack the animal's navigational ingenuities and find consolation in our own ingenuities -- maps, sextants, compasses. Nevertheless, from the moment we grant the possibility that man is a territorial species, then we must begin to wonder about this force called home. What is this thing that I shelter within me and share with citizens of most ancient seas? If I am to know and respect the dedication that is mine, then I must know and respect the green turtle's.

Here and there throughout the tropical world from [110] Borneo to the Caribbean are beaches, usually remote, where the old monsters come out of the sea to lay eggs in sandy nests. Where do they come from? The mature green turtle, like a cow, is herbivorous and must have its pastures of turtle grass in shallow, coastal waters. But such feeding haunts are rarely to be found in the vicinity of those beaches where turtles come to mate in the surf and lay their eggs in the sand. Archie Carr, professor of zoology at the University of Florida, became so intrigued by the question that over a period of years he tagged thousands of turtles on a beach in Costa Rica, and found that when nesting time was over the turtles would reappear at feeding grounds from Venezuela to the Florida keys.

Was it by simple chance and random wanderings that turtles from all over the Caribbean gathered at a particular nesting beach on the Costa Rica shore? It seemed unlikely. No turtle tagged by Carr on Tortuguero Beach ever returned to another nesting beach in the area. For those turtles who came, this beach seemed home. But how did they find it when every two or three years the reproductive urge came their way? Carr's curiosity led him on to make the discovery which we shall inspect here. He published his findings in 1965, and they may be regarded as science's last word -- or dying gasp -- on the homing of animals.

Ascension Island is in mid-Atlantic between Africa and South America. On it is a famous green-turtle nesting colony spread over several beaches. But on Ascension Island there is no least pasture of turtle grass, nor do such water meadows exist closer than the lush Brazilian shore. By tagging, Carr and his student Harold Hirth found that female turtles laying eggs on Ascension's beaches had come from Brazilian pastures 1400 miles away.

We must look at this journey from the green turtle's point of view. It is all open sea without an island or reef or shallows or other landmark. The equatorial current comes from Africa and is of no assistance. Ascension Island is a target just five miles across, with its loftiest point about one mile high. Until the invention of modern navigational aids, the island was difficult for human mariners to find. Yet the green turtle, who can lift her head but a few inches above the water and cannot see the island until she is a few miles offshore, finds it after a voyage of 1400 miles. And she not only finds it, but apparently finds it again and again. Five of the turtles tagged in 1960 have returned to [111] Ascension at a later breeding season, four to the same beaches.

How do they do it? And how did they ever start doing it? The green turtle, of course, is so ancient that its ways may have been determined before the continents assumed their present shape and relationship. But as to how the memory of home can direct innately the journeys of animals, we have no answer. It is a question with which science has struggled manfully. It is a question as profound as any which biology faces today, for within its unknown answer must lie qualities and properties and potentialities of which we have no least knowledge. Yet it is a question which scientists, with the sublime exception of a few like Carr, have largely abandoned.

When I was a young fellow in and out of the New York theater, a giant musical comedy opened at the old New York Hippodrome. It was a circus spectacle, and its name was Jumbo, and its two most spectacular stars were an elephant and that ageless miniature of a demented man, Jimmy Durante. And there came a moment in the show when Durante had a line worth recalling now, as we think of the green turtle, the Alaska fur seal, the sciences, and even of ourselves. The moment came -- a moment which a playwright might be tempted to describe, technically, as the obligatory scene -- when Durante stole the elephant. He entered from the shadows upstage, tiptoeing, making shushing noises at his vast companion. And when all seemed well, he encountered a policeman. Durante shrank. The policeman glowered.

"Where did you get that elephant?" growled the policeman.

Durante looked all about, blank, disturbed.

"What elephant?" he said.

What elephant? is the harried, half-demented reply of the sciences these days, when you ask them how animals find their way home. [112]

The "homing problem," as it is discreetly referred to, did not truly exist fifteen or so years ago. No one had yet related it to territory, and there was a prevailing assumption that those animals, like pigeons, demonstrating a remarkable capacity for finding their way home were guided by nothing more inexplicable than a remarkable memory for landscape. Terms like "homing instinct" and "migrating instinct" were used, but loosely, and were intended to identify creatures relentlessly determined to return to familiar places, rather than to explain how they did it. It was assumed, for example, that in flocks of birds migrating over intercontinental distances to specific breeding grounds, there must be always those experienced older birds who showed the way. The young ones, next year, would be the wise ones. [113]

A few disturbing experiments, it is true, haunted the blue scientific sky like little black distant clouds refusing to abandon a happy, well-organized picnic. As far back as 1931 O. J. and A. Murie, able naturalists, had come back from Wyoming's Grand Teton Mountains with some observations not easily explained. They had spent a summer in the high forests of fir and lodgepole pine trapping and retrapping deer mice. It is a standard technique for determining the range of small mammals. Live traps are set every so far apart, according to a pattern, over a fair-sized area. When a mouse or vole is trapped, he is marked and released. After the same individual has been retrapped enough times, and each location of his forced detention recorded on a chart, the observer gains a reliable notion concerning the limits of his range. The Muries' investigations led to some questions about homing for which there could be no sound answer except, What elephant?

Trapping and retrapping demonstrated that the tiny deer mouse rarely leaves a range fifty yards in diameter, and that one hundred yards is just about his lifetime limit of wandering. This area might be described as the world view of Peromyscus maniculatus. Yet when the Muries turned their attention to homing, some wonders showed up. Five deer mice were able to find their way home from a distance of one mile. Knowledge of the terrain was impossible; nor does the deer-mouse way of life, any more than the green turtle's, make attainable a bird's-eye view of a problem. Also, if you are the size of a deer mouse, then returning one mile is a little like returning from the other side of the world.

The Muries noticed that the best travelers in their collection were usually sub-adult, those with the least experience. And so they selected a young female, one about five weeks old. A deer mouse that age never leaves the immediate vicinity of the nest. This one, transported two miles, reappeared contentedly in her home trap in exactly two days.

Several other early if less spectacular studies went into the literature. C. M. Breder, Jr., later to become director of the New York Aquarium, as far back as 1927 was puzzling over the navigational capacities of frogs and toads. A German investigator demonstrated that when a dog returned eight or ten kilometers to his home, over largely unknown terrain at a certain recorded speed, he could only have come [114] on a beeline without time for scouting around. One student confirmed a general fish rumor by marking steelhead trout. Of 238 caught when they returned to spawn, 233 were in their home stream, only five in a stream four miles away.

Little black cLouds definitely hovered about the horizons of the scientific picnic. Besides deer mice and frogs and steelhead trout there was always, of course, the Eel Story. But the Eel Story was a little like Hitler's Big Lie. Nobody could possibly take it seriously. I have checked into every corner of the Eel Story, and I know that it is true. Nevertheless, were I to be sitting down to eat smoked eel tomorrow, I should still not believe that what I was eating had spent its youth in the Sargasso Sea. I do not even believe that there is such a place as the Sargasso Sea. When I was a boy I saw a film called The Isle of Lost Ships, and its scene was the Sargasso Sea, where all the seaweed in the Atlantic winds up in a warm, enormous eddy. According to the movie, all the lost ships wound up there, too, and there were Spanish galleons and wrecked clipper ships and old Roman galleys, and people lived forever, and there was Lewis Stone in some kind of costume. You went home afterward and could not sleep and lay in bed and listened to switch engines, somewhere, shunting freight cars around in Chicago yards, and you thought what a wonderful, wonderful world it was and how could you ever wait to grow up? But you did not honestly take the Sargasso Sea seriously, just as no sane scientist could ever take the Eel Story seriously. And I do not wonder.

It was a man named Johannes Schmidt who discovered that every eel in the Western World gets hatched in the Sargasso Sea. Eels are an important business in Denmark, and it was the Danish eel industry that supported his work over a period of some sixteeen years, until he published it in 1922. What was known about the eel was that in the autumn all make their way down the rivers of Europe to the Baltic or the North Sea or the Atlantic, and never come back. The following spring a myriad of baby eels -- called elvers, about two or three inches long -- appear off the coast and make their way to fresh water. It was also known that the American eel, a different species with a few less vertebrae in its back, did the same thing. What happened to the old eels? And where did the elvers come from? Nobody knew. A mild puzzler for the biologist, too, was that from Iceland to Cyprus there are no local races of eel. All of the [115] European species are a single variety, and all of the American the same. The biologists would have done well to stay mildly puzzled, and to have stayed away from Schmidt. Because he discovered that a very small, transparent, marine creature, Leptocephalus brevirostris, known from the Sargasso Sea, was in fact the eel larva.

It was, of course, impossible. It meant that all the mature eels in Europe, and America too, set out for the Sargasso Sea in the autumn, breed there in the spring, and die. The European larva takes two years to reach full size, and a third year to metamorphose into an elver, by which time they have sorted themselves out, and all the European elvers have migrated to Europe, where they have never been, and all the American elvers have migrated to America, where they have never been either. But how do they know where they are going? And how does an eel with 115 vertebrae know that he should report off the Dutch coast, and one with 107 vertebrae know that he should go up a river in North Carolina?

No bigger cock-and-bull story had ever hit science. The only trouble was that the Danes even provided Schmidt with a research vessel, and he proved it, and published the results in the Philosophical Transactions of the Royal Society of London, one of the staidest scientific publications in the world. Once in a while as the years went by, attempts would be made to disprove Schmidt's story, but they always failed. Only recently someone published in Nature a good, solid, environmentalist solution showing that in truth there is only one species of eel, that the larvae get caught up in Atlantic currents and deposited at their separate destinations, and that if you develop in cold water like a European elver you will have more vertebrae in your back than if you grow up in warm water like an American elver. In the manner of most good, solid, environmentalist solutions, it combined improbable biology with impossible statistics. Wynne-Edwards has since shown that if it were true that the number of vertebrae depended solely on water temperature, then a good many eels would have to come out of it with an in-between count. Yet there are almost none with 111 vertebrae, and very few with 110 or 112. Also, there are physiological differences between the two species.

Schmidt's conclusions still stand today, in giddy glory. And yet, as I have said, there is something about the Eel Story a little too much for human credulity, and had I [116] attended the scientific picnic, I doubt that I should have considered any such nonsense a threat to my afternoon. That is how it was, I presume, when in 1951 an excellent student named Lester Aronson, of the staff of the American Museum of Natural History, could come to no explanation other than landscape memory for the weird antics of gobie fish in the British West Indies. Since it was the last major study of animal navigation before the thunderstorm broke, let me describe it for its historical worth.

The gobie is a tiny tropical fish, about an inch long. Aronson first heard of its odd capacities from colleagues at the Lemer Marine Laboratory at Bimini. On this little island in the Bahamas, gobies frequent tidal pools, a yard or so in diameter, that pock the coral shore. And the rumor that came to Aronson was that the gobie always knows his way home and is never stranded by the ebbing tide. Aronson set up a study.

The problem of gobie navigation, as things turned out, was far more mystifying than just knowing his way back home. The tiny pools left behind by the fall of the tide are separated, many of them, by ridges of rock some inches higher than the level of the pool. The gobie, considering how small he is, is a stupendous jumper. Isolated in one pool, he leaps unerringly into the next. But he cannot from his position in the water have any means of knowing in which direction the next pool lies. How does he do it? Aronson concluded that trial and error was out of the question, since most errors would strand the gobie on fatal sun-baked rocks. Any kind of solar navigation was likewise out of bounds, since the gobie flips his way about with equal certainty on cloudy or sunny days. Nor could it be a matter of having learned, through one means or another, a tested path home. He takes different paths to or from the home pool, and, for that matter, is thoroughly independent of home. From any pool he leaps on any course always to safety.

Aronson concluded that there could be no answer to explain the gobie's navigational sense except that at high tide, when he is free to swim about over all the pools, he somehow comes to learn the topography. It was a reasonable enough answer in 1951. It was, in fact, the last sane, reasonable explanation to be made at the picnic before the storm broke. [117[

W. H. Thorpe, whose work on the relation of learning to instinct I have already mentioned, is one of the world's ranking authorities on animal behavior; he is also the authority least satisfied with a "What elephant?" approach to the homing problem. He has provided at his department at Cambridge University a safe anchorage for restless, roving spirits bent on torpedoing biological calm. The most restless of these was a man named G. V. T. Matthews, who in 1951 began methodical experiments with homing pigeons. He published his first conclusions in December of that year.

Homing pigeons, as used in races, are trained for the course. On release after release the trainer takes his flock farther and farther from the home loft, always in the direction of the ultimate racing release point. From such experiences had grown up the assumption, when Matthews went to work, that pigeons home through learning the landscape. It had occurred almost to no one, at this date, to experiment with untrained pigeons. But it occurred to Matthews. And he came up with the insane conclusion that inexperienced birds, who can have no knowledge of the point where they are released, orientate themselves better than trained birds who presumably know just what they are doing. We may recall the Muries' observation, twenty years earlier, that the sub-adult deer mice were the best homers.

A trained homing pigeon may know the landscape in the vicinity of his loft better than the inexperienced, and may find it more quickly once he has arrived in home precincts. But Matthews divorced from what might be called a finding capacity, the capacity to orientate, to set a navigational direction when released. He devised quantitative means for rating his birds. Having been thrown straight up at the release point, the bird would circle once or twice before setting out. Matthews kept his bird records on a basis of the angle of deviation from the true course, and the time it took the bird from the instant of release to reach the vanishing point, usually about two miles. In every department, the inexperienced birds made better records than the experienced.

How could one explain it? Only by assuming that the navigational capacity is innate and in some birds may become confused by experience. The genetic basis for homing [118] was further confirmed by Matthews' observation that some individual birds will be superior navigators from their first trial, others poor; and their capacities will change little with experience. So far as success at returning to the home loft was concerned, it mounted rapidly with training. The bird indeed formed a sharp recollection of the landscape in the area of his home, and developed with training a larger and larger geographical target familiar to him. But there was a clean line between this learned ability and the ability to choose a correct course when released in an unfamiliar countryside. Initial orientation seemed an inborn capacity, varying in individuals, and benefiting not at all from experience. ,

About the same time that Matthews was conducting his experiments with homing pigeons at Cambridge, a man on the Continent named Gustav Kramer, of the Max Planck Institute, was conducting comparable experiments with starlings and relating the migratory instinct to the homing capacity. At a station on the East Baltic coast Kramer observed that starlings in an outdoor aviary all attempted in October to escape to the southwest. Southwest is the direction of starling migration at this season. And so Kramer built a round aviary without any view of the horizon or identifiable landmarks. The starlings still tried to escape to the southwest.

Things were beginning to get jittery. To say that the capacity to home, or to fix a migratory direction, is innate is to say approximately nothing. One still must ask, how do animals do it? By demolishing the assumption that animals navigate by memory and experience, Matthews and Kramer upset a scientific applecart. By demonstrating that it must be instinct, they set up a new one. What instinct? How? Kramer disposed of one possibility: that the animal is somehow susceptible to magnetic fields, and harbors-within him a biological compass. Near his East Baltic station were deposits of magnetic iron ore that rendered unreliable the reading of manmade compasses. "The compass here," he observed, "behaves drastically. The starlings do not."

At the same time Matthews was perfecting his own disposal system for the same possibility. To the legs of one group of pigeons he attached small magnets, sufficiently strong to confuse the earth's magnetic field. To a control [119] group he attached similar ballast, but of brass. All were released, all returned with equal success. But at this point in Matthews' investigations I suggest that the reader cease to envy the fascinating life of the experimental animal, and in particular the lives of Cambridge homing pigeons.

A hypothesis had popped up that perhaps good homers do have a remarkable memory, after all, concerning the route taken from the loft to the release point. Their capacity is for retracing a route. It was a hypothesis conceived in a sinking position, but Matthews was prepared to torpedo anything. And.so he devised a demonic bit of machinery which must in some details have resembled a concrete mixer. He installed, the device in a closed truck, and installed his pigeons inside the concrete mixer. The machine turned over four times a minute. And so, while Matthews cheerfully drove his feathered charges the seventy-five miles to the release point, inside the machine pigeons were being dumped on their heads regularly every fifteen seconds. It was not a course that any would be quite likely to remember, let alone choose to retrace. And when released, all flew directly to their loft in profound relief that this newest hypothesis had been disposed of.

Then there was the sun hypothesis. Matthews observed that on cloudy days his pigeons made very poor records. The sun, therefore, at least with pigeons, had something to do with it. (Although we may remember that Aronson's gobie fish did just as well with their leaping on overcast days.) The immediate explanation was that pigeons, normally released about the same time of day, develop a memory for the proper angle of the sun in relation to course. The proposition would not explain why untrained pigeons do so well, but Matthews, as usual, would try anything. He trained two sets of pigeons, both at the same hour of the day. Then he released the control group at the normal hour, the experimental group six hours later, with the sun 90 degrees away from the familiar. All came home, unperturbed.

By now the ghostly outlines of the "What elephant?" question were beginning to develop. Was it possible that a pigeon while it circled once or twice after being released took a moderately accurate sailor's reading of the sun? But this would require not only an inner sextant but an inner chronometer. An animal capacity for sizing up the sun's

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angle might be granted; but the angle is meaningless unless 1 one knows what time it is. And while there are such organic ] realities as the biological clock, the demand on the pigeon | for accuracy seemed a little exorbitant.

We are beginning to know a little about biological clocks. I It is the sort of thing that disturbs you when you fly from 1 Los Angeles to Paris directly and have to take to your bed | in consequence. The eight-hour change of time, accom- 1 plished in a jet in approximately the same number of hours, I puts your biological clock out of order. How primitive is 1 the clock may be judged by Best's observation of his brain- I less, rectumless planarian worms. There is one species, 1 Dugesia tigrina, that preys on another species, Cura fora- 1 mani, but only at night. Best kept his Washington laboratory 1 at a constant temperature of seventy degrees Fahrenheit I under constant fluorescent illumination. There was no way I to tell night from day. He fasted his predators under these conditions for ninety-eight hours, then put them in a tank 1 with their prey. The planarians knew what time it was. Between six a.m. and six p.m. he recorded only two attacks; but when theoretical night came, there were nineteen.

The biological clock is a reality. But does it keep time I sufficiently well to enable a pigeon, circling once or twice after its release, to determine its latitude and longitude? By 1953, growing a little desperate himself, Matthews came to the conclusion that the clock was good enough; that there was no other explanation. Then in 1955 another roof fell in.

Duke University, in North Carolina, has maintained for decades a Parapsychology Laboratory dedicated chiefly to the investigation of that scientific shady lady, extrasensory perception. There a man named J. G. Pratt investigated Matthews' investigations. Basic to Matthews' conclusions had been that the pigeons needed a little time to circle for the purpose of taking solar observations, reading their biological clocks, and putting their computers in order. Pratt suspected that the pigeons circled simply to gain altitude. And so he took his pigeons seventy-five miles from their loft to a town where there was a fire tower one hundred feet tall. Half of his pigeons he released from the base of the tower, half from the top. The half released from the ground circled, and took about five minutes to reach the vanishing point two miles away. The pigeons

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released from the top of the tower set straight out and reached the vanishing point in three minutes.

The shock waves reached back to Cambridge. R. H. Thouless was sent out to check on the experiment. The United States Navy, probably wondering by now whether all the money being spent on sextants and chronometers was really necessary, put up part of the funds. A new, more complex experiment was set up. The birds were released from forestry towers sixty to one hundred feet tall. Some of the.birds were in covered crates which made it impossible to glimpse the sun until the instant of release. And Pratt and Thouless agreed that these averaged ten seconds to set their course.

Since homing pigeons become confused on a cloudy day, there can be no doubt but that the sun, by some means or another, enters into their capacity to navigate. Thorpe himself, however, has published the estimate that for a pigeon to make such a determination of position in ten seconds, his biological clock would require an accuracy of plus or minus two minutes in twenty-four hours. And in fact, by 1955, biology was getting into such an uproar over homing that the prejudice of the pigeon in favor of sunny days was beginning to mark it as a backward, insensitive, relatively unenlightened species.

Somebody looked into Scottish brown trout, which spend their first two years in streams, then migrate to a loch in October when the adults come upstream to spawn. The following spring the maturing trout return. Of 3000 trout marked in five tributaries of a Scottish loch, only one made a mistake in the spring. Somebody showed that black-headed gulls, taken from their nests and put in cages in a windowless shed with no external clues as to direction, will concentrate their escape reactions on the direction of the nest. Somebody wondered about sky polarization, which seems to help bees. Somebody else showed that birds, unlike bees, have the wrong kind of eyes. Somebody wondered about ultra-shortwave radiation. Somebody else showed that birds have no reaction to it. Somebody even wondered about the Coriolis effect, produced by the earth's rotation, which is rumored to make the departing water in your bathtub swirl in one direction in the northern hemisphere and the opposite in the southern. This seemed a most penetrating suggestion, since no one understands it anyway; but

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somebody else put the Coriolis effect down the drain.

These were trying times. Gustav Kramer, impatient with concerns about the sun, pointed out that barred warblers migrate only at night. What about the moon? An unhelpful professor named R. Drost pointed out that migratory birds have no difficulty whatsoever in finding the minuscule island of Helgoland on moonless nights. A desperate German scientist turned a flock of birds loose in a planetarium; they homed.

Somebody even brought up territory.

Homing and territory are related concepts. For the layman, freshly approaching the materials of the new biology, the relationship must stand forth as clearly as the silhouette of poplar trees standing beside a favorite grandmother's house. Yet in the scientific literature one can find few mentions of it.

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When W. C. Allee and his associates in 1949 published their classic textbook Principles of Animal Ecology, they seem to have taken the relationship for granted. "Territoriality includes homing or the defense of a given area, or both." As I have already mentioned, however, Allee's great field of authority did not include territory. His judgment was ignored. When some years later J. D. Carthy published Animal Navigation, the only book we have presenting a general review of the subject, territory went unmentioned. This was\ in 1956, probably just a bit early for the more unreasonable dimensions of the problem to have homed to the book's able author. So far as I know, the first clean-cut statement of the relationship had been made only the year before by the English ornithologist James Fisher at a meeting of the International Ornithologists' Union at Basle: "Just as seabirds home to the colony of their birth, so do passerines home to the territory of their birth."

Fisher's statement was a challenge to science. Just what do we deal with when we consider this force called territory? We have seen that it may act against the interests of the individual, that it may restrain his freedom of action and tie him to those responsibilities which he might otherwise avoid. We have seen that in some as yet inexplicable fashion it contributes to his resolution and his energies, even as it inhibits the energy and the confidence of those who would intrude. And we speculate that in fair probability what is true of lower animals is true also of man. What, then, is this force that acts on us? What are its farthest dimensions? Is it possible that, as Fisher implied, territory is the magnet directing the animal compass?

A series of experiments and observations gave strong indication that Fisher might be right. Green sunflsh attracted the attention of investigators in the University of Wisconsin's zoology department. It had been determined earlier that the tiny sunfish are intensely territorial, that females are as aggressive as males, and that all defend properties when still so immature that neither sex nor breeding can have anything to do with it. Now the Wisconsin team became attracted by the activity of the little belligerents in country ponds. Tagged fish, trapped in the autumn, were unable to return to their home areas through the four winter months when the pond was

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frozen. Yet nine out of ten would so return when spring brought its thaw.

Such an attachment to the homeplace seemed worth looking into. How did they find their way back? By random hunting or by true, direct-course homing? To trace the navigation of small fish in large ponds offers a problem, but it was solved by an idea as ingenious as it was inexpensive. Ping-pong ball floats were attached to captured sunfish at the ends of threads. Fish were released in the center of the pond. The ping-pong balls bobbed, then like a fleet of tiny patrol boats under orders from central command headed each on its way home. No random hunting or zigzag uncertainties marred the voyages. Sunfish truly home, and home to territories.

Another observation, this one in the Aleutian Islands, confirmed Fisher's thesis. Karl Kenyon is a biologist, today with the American Wildlife Service, who has done as much as any man to render presently insoluble the problem of animal navigation. The first of his contributions was a study of the Alaska fur seal, which, because of its commercial importance and long-threatened extinction, has been an object of scientific attention for many decades. Tagging has demonstrated that as green turtles converge on their nesting beach, seals return again and again to the same rookery when calving time approaches. The bulls

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come first, to joust for territories in the island rookery; the cows come later, having completed their long passages from all over the northern Pacific shores. She arrives pregnant, and so chooses not only the birthplace of her present burden but the genetic future of her next-born. What will be the criterion of her choice?

I recorded earlier the results of Bartholomew's brooding about seals: the cow could not be less concerned with which bull will become her lord and master; what attracts her to a territory is the sociability of other cows. But Kenyon, through remarkable luck, found evidence that, whatever bull may attain mastery over a property, the cow tends to return to the territory where she was born.

Kenyon made his study at Polovina Rookery on St. Paul's Island in 1954. His luck was to find a photograph of the rookery made in 1896. The photograph showed virtually the same distribution of harems, large and small, as almost sixty years later. The distribution was quite unrelated to topography, despite a significant change which had come about. In 1898, out of concern for the welfare and number of baby seals, what might be called a slum-clearance project had been inaugurated. Earth had been filled in and areas leveled to extend the rookery's space. But in 1954 the improvements of 1898 were yet unoccupied by harems. Nothing, evidently, could induce a cow to choose a birthplace for her calf other than that of her ancestors.

The female seal homes to that territory where she was born. But let us look also at salmon, another species long studied because of its commercial importance. There is no more famous or inexplicable animal migration than the upriver spawning run of the salmon. Even by the 1920's it was established that salmon return not just to the general area of their origins but to the same stream and even portion of stream. How do they find it? How, after two to six years at sea, does the salmon find its proper river mouth and then trace its way through perhaps a thousand miles of dividing tributaries on a course that will lead it home?

We do not know. There has been the memory explanation, as in homing pigeons. But, as Thorpe has pointed out, if a salmon is to memorize all the twists and turns and junctions on his way downstream, then he must unreel it all backwards on his return perhaps six years later. A. D.

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Hasler and W. J. Wisby, who gave us the green sunfish and their ping-pong balls, have advanced the taste hypothesis, the reasonable suggestion that if you are a salmon then all streams taste differently. Fish entering the Columbia River mouth, for example, simply keep going whichever way the water tastes more like home until at last they arrive at the unadulterated, undiluted memory of youth. But there is a problem. Evidence indicates that, wherever he is in the broad blue sea when the spawning urge strikes, a salmon lays a direct course for his home river. How can the taste of home waters guide him through the generalized flavor of sea water?

The navigation of salmon remains as closed a secret as does the navigation of homing pigeons. But in 1962 the authoritative Dutch journal Behavior published a heavily documented study of the territorial activities of juvenile Atlantic salmon, and the Fisher hypothesis again flashed forth. Are the fish returning to definite territories?

The observations were made in Canada, partly in the field, partly in the laboratory, by M. H. A. Keenleyside and F. T. Yamamoto. The study related not at all to homing, but rather to the previously unknown behavior of immature fish before they set out to sea. Reaching that stage is a tediously long process, a year or two in the warmer streams, as much as seven in the colder. Yet from his earliest, newly hatched, free-swimming moments until at last physiological development makes possible the wider life at sea, each young salmon has his defended territory. Normally he lingers near the bottom of the stream, feeding or chasing intruders; after every chase, however, he will return to his precise station. Even in the fastest river currents he will swim upstream at a rate which maintains without variation his relation to a fixed spot in the stream bed below. And he will do this for the entire period of his immaturity, be it two years or seven.

Why? When asking such a question in biology, of course, what one means is, What is the selective benefit to the species of maintaining territories under such difficult conditions for periods so long? No answer which we have encountered thus far can, I believe, explain it. The investigators favored the food theory -- that the division of available space between an appropriate number of young salmon assured food supply for each. This could be true

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in a still pond, but in a rapidly flowing stream bringing continually fresh supplies, the answer seems dubious. Besides, many fish species travel in dense schools without creating a food shortage. The Canadian observers, however, faced a severe problem, for if it was not division of food giving survival value to such extreme behavior, then what was it? Neither sexual rivalry nor protection of offspring could have anything to do with it. Security from predators seemed unlikely. Why would natural selection demand of a baby fish that from his first swimming days he define a small area of stream bottom, defend it as his alone, and against a rapid current swim without an instant's variation of pace for a term of years, keeping himself in absolute relationship to a few pebbles on the bottom?

To me, of course, there can be no answer but homing. Those who succeed in their youth at playing this natural, infinitely demanding game of territory will return to spawn. Those who fail, on the other hand, will in some fashion lack sufficient motivation to return and so will fail to reproduce. How the sexually mature salmon finds his way back remains as great a mystery as ever, but why he returns, what environmental consummation he seeks before he can reproduce his kind, becomes a bit less obscure. Homing is another extension of the territorial power.

That natural selection should encourage in certain species such extraordinary capacities could have made no sense to orthodox biology. It is population genetics -- the foundation of modern biology and its chief revolutionary agent -- that furnishes us with our explanations and makes probable the Tightness of James Fisher's thesis. Yet population genetics is a science so new, and so forbidding in its theoretical complexities, that we tend to label it "Unfit for Human Consumption." It would be unwise, certainly, for you and me at this stage of our inquiry to enter its mathematical labyrinth; we might never come out. Nevertheless, if we are to grasp the profound link offered by animal navigation to territory and reproduction, then we should knock around at the doors of population genetics even if we do not go inside.

In the year 1930 the work of three of the world's most eminent geneticists was coming to a conclusive crisis. Two were English, R. A. Fisher and J. B. S. Haldane, and the third was an American, Sewall Wright. All were mathe-

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maticians, and all, in the course of two years, published books or papers setting the theory of evolution on a new course. Th"Ough their collective mathemat'cal genius they drew on the principles of heredity as discovered by Mendel to establish the precise structure of mutation and selection in relation to evolutionary change. It was something that had always eluded Darwin, and the consequent renovation of Darwinian thought made possible the new biology.

Population genetics, raw food that it is, may be best assimilated in such digested form as is offered by Julian Huxley in Evolution: The Modern Synthesis or by George Gaylord Simpson in Major Features of Evolution. Its prime principle, however, is simple enough: the basic evolutionary unit is not the individual but the population of which he is a part. I have used the term again and again, and it will be just as well if we now define it. A population, in biology, is a reproductive community. More sharply stated, it is any group of individuals who have a modest probability, within any generation, of meeting and mating. Where high improbability takes over, there lies the border of the population.

We have seen the kob divided invisibly into breeding populations through the attraction of the stamping ground. We have seen it in ruffs, and in Wyoming's sage grouse. We shall see that in almost all species there are barriers -- what biologists call "reproductive isolating mechanisms" -- separating individuals into these reproductive communities. While in theory any two members of a species may meet, mate, and produce fertile offspring, in fact it does not happen. Even in the human species such barriers as language and religion, geography, provinces, nations, tribes, classes, occupations divide us into a visible or invisible mosaic of reproductive communities. Our increasingly fluid societies of the twentieth century, our increasing ease of travel and communication and of geographical migration in search of work or education, tend all to break down these barriers and provide wider mating choice. But if we view the human species in terms of its teeming billions, we must see that this widening of choice, as of our day, remains statistically insignificant.

It was Sewall Wright who explored most deeply the relation of the population to evolution, and demonstrated mathematically its necessity as a reproductive unit. Let us say that an animal population is subjected to a change in

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climate making advantageous any genetic change in the direction of heavier fur, resistance to new diseases, or capacity to live off novel foods. Natural selection will direct that those individuals with superior endowment will be more likely to survive to maturity, reproduce, and so in a given number of generations spread their fortunate endowment through the whole population. What was at first the genetic equipment of a few individuals has become a portion of the population's "gene pool."

Now, let us suppose that the population is fairly small, say a thousand individuals; then it will not take too many generations to spread the advanced genetic equipment through the entire interbreeding community. But what if there were no isolating mechanisms? What if the entire species interbred with equal probability? The local group, facing local environmental demands, would be unable to conserve genetic advantage within its number and would see with every generation the dilution of its environmental answers in the broad sea of species interbreeding. Sooner or later the population would face extinction.

The American geneticist Theodosius Dobzhansky has written, "The biological function of all reproductive isolating mechanisms is essentially the same -- inhibition and eventual stoppage of the gene exchange between populations. . . . Without reproductive isolation, species would disappear, submerged in a mass of genetical debris."

We have most of us grown up with the older notion that inbreeding is harmful, and such statements from the population geneticists may bring us unease. It was Sewall Wright, in a triumph of theory, who synthesized the two views. Long before we possessed observations of natural animal populations which might have checked or contributed to his conclusions, Wright through purest mathematics calculated that to attain an ideal evolutionary balance there must always be those two or three males, out of every population of a thousand, who go astray and deposit their genes in the next population's pool. Observation has almost perfectly confirmed it. Buechner found that five males, in two years, reappeared in other populations of Uganda kob. There will always be that odd roebuck who does not return in the autumn but stays on in another forest. Of homing fish there will be always a few that return to the wrong stream yet manage to breed. Accident and adventure, forgetfulness and rebellious disposition

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all combine to realize a natural design which our genetic necessity imposes.

However complex may be the equations of population genetics, simple words tell their story: the material of the evolutionary process is not the individual but the population; not my genes or yours, but that more enduring, more immortal entity, the pool of genes from which I was conceived and my possibilities determined, and to which I shall contribute through my children and my children's children. Here is the vital entity which must continue, through an infinity of years, to meet the exigencies of daily need and the contingencies which the world sets up on it. You and I are the accidents of a night's union. You and I, in evolutionary terms, are expendable. If you or I fail in our ambitions and our purposes, evolution shrugs. But if you and I and too many others through our failures bring damage to the sum of a population's genetic potential, then that is another matter. It is the population which will be here when you and I are gone; it is the population which holds membership in life's immortal club and must adjust itself to new rules, new regulations; it is the population, as a biological reality in evolutionary space and time, which must meet the full rigor of natural selection.

It is the population, in other words, which is evolution's intermediary between the individual and an unborn posterity. And, viewed from such a perspective, many an observation of the new biology begins to make sense. That an animal may through innate compulsion act against his personal interest; that creatures of the arena may through their losing be subjected to psychological castration; that the male of a pair through his attachment for territory may be held responsible for offspring: all such phenomena, which I call expressions of a biological morality and see enforced by the territorial imperative, exist as commands of the population. It is not enough to seek explanations for behavior in terms of individual interest. If the welfare of the population is the final value of natural selection, then it must be assumed that selection will have favored those innate behavioral patterns and capacities in the individual, however extraordinary, which in turn favor the population's good.

So it is with homing. If the integrity of the reproductive unit is to be preserved, then any animal species which for reasons of food supply or physiological development or

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getting away from a hard winter must disperse its populations far from their breeding grounds will develop, as a selective necessity, means of finding the way home. Two factors must as a rule exist: a territory or cluster of territories commanding the loyalty of a population and serving to isolate it from all others; and an innate navigational mechanism, whatever it may be, that with unfailing accuracy will direct the return of the population's most far-ranging citizens to their ancestral acres when breeding time draws near.

There are exceptions. I can hear a derisive voice in the back of the hall crying out, "Very good. And how are the eel territories doing these days, down in the Sargasso Sea?" And I can recognize in myself the half-demented posture of science and the impulse to look in all directions and reply, blankly, "What eel?" The preposterous animal most definitely homes to a seagoing swamp southeast off Bermuda where no likelihood at all can exist that he possesses or ever possessed a home of his own. Neither does there seem much likelihood that eels there sort themselves out into populations; they interbreed, we believe, as a species. But we must recall that the eel is a creature even more ancient than the green turtle and may have perfected his ways before innovation took the course of evolution in other directions. If this is the answer, then it is also worth recalling that, despite his antiquity, the eel is no less susceptible to the powers of animal nostalgia which invest his sunset days in some comfortable, brackish, northern European pond and direct him to return across the comfortless Atlantic to breed and die where his life began.

We do not, of course, understand the eel any more than we understand the primitive nostalgia that brings assurance to a brainless planarian worm and permits it to feed more quickly and freely in familiar places. We may speculate that it is this ancient nostalgia which natural selection has organized into the territorial power, the capacity to navigate, and the evolutionary device of the isolated breeding community. But we do not know. And the pity of it is that the sciences have all but surrendered in their efforts to find out. A few hardy souls like Archie Carr may still persist, and may contemplate the fixing of radio transmitters to green-turtle backs and observation from whirling satellites. But biology as a whole, despite the theoretical aid which population genetics has brought to the subject,

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has been tempted to sweep the homing problem under the rug.

I cannot wonder that biologists tend to shy away from a challenge so mighty. When neither sun, moon, stars, magnetism, polarized light, the flavor of rivers, or the swirl of water around a bathtub drain offers sufficient mechanistic explanation for a form of behavior so observable, so measurable, then anyone must be tempted to change the subject. But as we inspect a few more examples of these farther shores of animal capacity, and we keep in mind its linkage with the territorial power shared even by man, we may ourselves be tempted to hope that science will soon gain its second wind.

4

The man named G. V. T. Matthews, who made everyone so much trouble with his Cambridge homing pigeons, came down with another catastrophic idea. It was to investigate the capacity of sea birds to navigate over land. Having afflicted the peace-loving occupants of his Cambridge lofts with every device from magnetic ballasts to out-voyage concrete mixers, he retired to an island named Skokholm, off the coast of Wales, to make a nuisance of himself with the local shearwaters.

The Manx shearwater is one of some 200 species of sea bird who nest in dense colonies in unlikely places. He is a bird with a belligerently proletarian look, mostly dull gray and white, and a turned-over beak like an old-fashioned socialist determined to stir up an argument. His life experience includes only the sea and the breeding colony where he nests in a burrow with his mate. Matthews subtracted from several hundred burrows one parent each and distributed them to various British release points, all of which demanded a return flight over land. Only a few found the novel navigation a problem. The general success was to be expected at this stage of disintegration of old assumptions concerning homing. But what impelled Matthews to send off two birds to Boston -- whether curiosity or simply a sense of mischief -- I do not know.

The Boston birds were sent off by transatlantic airliner, and one died of injury. The other, however, with the name tag AX 6587, was released at Harvard University by a

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group of zoologists all suffering, we may assume, from the suspicion that this was going a bit far with dumb animals. That was on a June 3. On June 16, twelve and one-half days later, AX 6587 was back with his mate in the burrow on Skokholm Island. He had covered 3050 miles at an average speed of 244 miles a day.

While AX 6587 was a bad blow to science's prospects, he did not quite finish off the efforts to find a reasonable explanation for homing. There were to be two more major encounters between man's capacity to explain and the animal's capacity to confuse. And these, one voluntary, one involuntary, were enough, it seems, to finish man off.

The voluntary encounter occurred when the International Geophysical Year met the Antarctic skua. There

were few bird watchers among the many scientists who adjourned to Antarctica in that year, but there was an abundance of boredom and at most stations no creatures to relieve that boredom but the skua and the penguin. Sympathies were quickly joined, since all adored the penguins and hated the skuas who preyed on the penguin young. And so, as a by-product of the physical sciences' immense project, there came about one of the widest bird studies ever made. Teams from the Soviet Union, the United Kingdom, the United States, and many other countries cooperated to band and keep track of 6000 specimens of the world's most disreputable bird.

The Antarctic skua, like the great-crested grebe, is a bird of old origins, descended probably from the common stock of plovers and gulls and terns and guillemots. He is

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a giant, with a wingspread of almost five feet. Like the albatross, he takes a long time to grow up -- five years -- pairs for life, is monogamous, and returns again and again to the same breeding colony where he was hatched. So far as I know, he has but one charming way. When the polar winter closes down and the breeding season ends, the skuas disperse all about the rim of the Antarctic continent to follow the icepack and live off marine life. Pairs break up, and he may feed in McMurdo Sound, she a continent away. But when October comes, and the Antarctic springtime, both return to the area of the colony. If both have survived, then he finds her or she finds him, and domestic life is resumed just where they left it when the great dark fell.

I can think of nothing further of an attractive nature to record about the skua. They return when they do because the Weddell seals are pupping in October, and he and she have an insatiable appetite for seal placenta. About then the Adelie penguins are beginning their inland march to the breeding grounds. The skuas follow, preying on the weakest. When the penguins settle down and build their nests, the skuas establish their traditional breeding ground on the outskirts of the penguin colony, thus making egg-stealing as convenient an entertainment as possible. Penguin tradition demands that Adelie females, having laid their eggs, return to the sea for a few weeks, leaving the males to guard and incubate them. This is a time of total warfare between skuas and penguins. Then the females return, freeing the males to go off to sea, there to feed and put a little fat onto their emaciated frames. At the colony the eggs are hatched and females now battle to protect the chicks. It is a hard life, in the Antarctic; and it takes a hardhearted scientist, far from wife and children, to resist a passionate alliance with the beleaguered penguins against the diving, devouring skuas. In all fairness to the skua, however, we must keep in mind that the penguin chick does not receive his exclusive attention. He preys on and devours chicks of his own kind with an appetite just as hearty. The Antarctic skua is one of the few cannibals among nonhuman species.

Carl Eklund, who was an ornithologist with Admiral Byrd's earlier expeditions to the Antarctic as well as with the American team during the International Geophysical Year, believes that the cannibal tendency in the skua may

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have increased the selective value of a tight territorial defense. His territory is large, about fifty feet in diameter, and he defends it against anything that moves by every means at his disposal. And his means are considerable.

Readers of African Genesis will recall the experiences of C. R. Carpenter with the howling monkey in Panama. Tradition had it that the howler would defend his arboreal territory by the lowest of means, even urinating and defecating on intruders below. Carpenter found through many an unpleasant experience that tradition was quite correct. Similar experiences have confronted the scientific observer in the Antarctic since the earliest explorations, for the skua is the howling monkey of the world of birds. And skua tradition is correct as well.

Herbert George Ponting was photographer with Commander Scott's tragic expedition to the South Pole in 1911. Ponting recorded in his notes, concerning the skua: "By outward and visible signs, the skua-gull is a gentleman, and his mate a dainty, well-dressed lady -- appearances being thus deceptive, for, except for their looks and cleanliness, there is nothing refined about either male or female; both are scamps and malefactors. . . . They would fly towards us from the rear and, carefully making allowance for speed and distance, discharge a nauseating shower of filth. I was more than once the victim of this revolting habit."

Eklund confirms it. The skua has two noteworthy means of territorial defense. One is to dive from a height and slam the intruder on the head with its claws. Eklund outwitted the birds by wearing a tall feather on his cap; the birds slammed the feather. But a feather is a poor defense against the alternative attack, a shower of well-directed fecal matter let loose with the most careful calculation, as Ponting had recorded, of speed, angle, and distance.

I do not believe that the inspiration to dump a few skuas at the South Pole was motivated by any simple desire to get rid of them. Such justification existed, and I can conceive of no more satisfactory disposal of a few of my own less-loved acquaintances than flying them to the South Pole, extending them a cordial farewell, and leaving them there. It seems, however, that when Robert Wood, of Johns Hopkins University, supervised the arrangements, he did so with higher scientific motives.

It was a most extraordinary test of animal navigation.

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Wood took six skuas from their nests on Ross Island, near McMurdo Sound on the fringe of the continent, and shipped them by plane the 825 miles to the South Pole. A distance like that may sound like the immediate vicinity as compared with Matthews' Boston shearwater. But we must think things over with care. The Antarctic continent, even in midsummer, is not the North Atlantic. At the South Pole the ice is two miles deep. Not for hundreds upon hundreds of miles will the least landmark puncture the flat white plain. There is even the matter of altitude, over 9000 feet, a considerable thin-air problem for a heavy sea bird who has never known anything but sea level. And there is the problem of north.

As one stands at the South Pole -- and may I assure my readers that I have never stood there, I am simply fulfilling my creative commitment -- one faces, in every direction, north. There is no choice. To the front, to the back, to the left, to the right, all is rtorth. The sun circles above an expressionless horizon. It does not set. It does not rise. The j sun offers no indication. Shall we grope in desperation for the Coriolis effect and the earth's rotation? Twenty feet from the South Pole a fixed point in the ice will move, with j the earth's rotation, 62.8 feet in twenty-four hours, and if I one can find a bathtub the water will go straight down j the drain without swirl or hesitation. What, then, shall j we do? Look to the stars? It is summer, friend, and they j will not return till fall.

One skua came back. What happened to the others, we j do not know. But in a matter of ten days one had re- 1 turned to his nest and his territory on Ross Island. How did he get home? It is possible that, despite the thin air, J despite the lack of landmarks, despite a circling deceptive I sun, he flew a dead straight course north -- which would i be in any direction -- until after a thousand miles he ar-fl rived at the continent's rim; then, doggedly following it 'i perhaps half the world around, he at last arrived home. It 1 is possible; but in ten days, and in the light of what we 1 know about other homing creatures, it is most improbable. 1

The encounter with the skua, which began with the j International Geophysical Year, was of a voluntary nature I and finished off with the accomplishments of a single bird. | The encounter between the United States Navy and the | Laysan albatross involved 100,000 breeding pairs, was wholly involuntary, and came to a conclusion as statistically

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convincing as it was embarrassing for both the Navy and science.

Midway Island became famous for the sea battle which took place in its vicinity at a major moment in World War II. It is a lonely atoll 1300 miles west of Honolulu, and until 1903 was nothing but a range of sandspits inhabited by neither man nor albatross. Then a cable station was established there, and its operators planted gardens, trees, shrubs. They were unaware that by making the island more attractive for man they were making it even more attractive for the nesting albatross. A breeding colony established itself. It flourished. And when Pan-American Airways established an airbase on the island in the 1930's, albatross enthusiasm seems to have known no end. Word must have been spread around all the mid-Pacific that Midway was more fun than anywhere; by the end of the pre-war decade there were 10,000 breeding pairs on Sand Island, the only spit large enough to accommodate a flying strip.

The albatross is a bird both unique and unfathomable of nature. He is not only unafraid of man but seems to enjoy our beastly companionship. It was because of this strange character that he became known to all the American fleet as the gooney bird. And it was his fearlessness, along with an uncompromising attachment to his bit of island soil, that was to prove the undoing of the United States Navy.

With the war, Midway emerged as an irreplaceable link in the chain of American air communications between Pearl Harbor and the Pacific's far-flung scenes of battle. The activity was sufficient, one would think, to discourage breeding activity in the hardiest of species. And it did so discourage the black-footed albatross, who declined in numbers. But the racket of aircraft and the jostling of men seemed only to stimulate the Laysan to more formidable nesting activity. By 1945 there were 30,000 nesting pairs sharing the sandspit with the United States Navy. And ten years later accurate counts placed the number at 60,-000, with 40,000 more on neighboring Eastern Island. By then jet aircraft had become standard equipment in the American defense establishment. And we need only recall, to visualize the problem of the Navy, that the albatross is a very large bird. It takes just one, sucked into a jet engine on take-off, to wreck a plane.

The reader, whether callous or thoroughly objective, may say, "But where's the problem? If it's human life or albatross life, then slaughter the birds." But this is to ignore the delicate sentiments of the American taxpayer, who would rise in outrage if he knew that his Navy was slaughtering innocent gooney birds in the middle of the Pacific Ocean. It is also to ignore the annual necessity facing the United States Navy to pry monumental appropriations out of the American Congress, an institution which would like nothing better than to take advantage of any popular outrage to denounce the Navy and cut its money. If the reader cannot take the situation seriously, he must accept it that the United States Navy did. .

By the middle of the 1950's a vast comic plot was taking shape on a stage as large as the Pacific Ocean. In the middle sat the United States Navy, sweating it out. On one side ranged the American people, the American Congress, and the nightmare of a public scandal. And on the other sat the gooney birds, fearless, trusting, immovable, breeding insanely, 100,000 pairs on tiny, irreplaceable Midway. The Navy decided to call in science. Two biologists from the United States Wildlife Service reported for duty. One was Dale Rice, the other Karl Kenyon, whose observations of the fur seal I have already reported. They were given all facilities, all most urgent encouragement. But their consequent study of the behavior of the Laysan

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albatross could have brought encouragement to none. One wonders how the United States Navy had the stamina to remain in business.

The Laysan albatross pairs for life -- a very long life -- and is as loyal to his mate as to his territory. In many ways it is a classic example of the pair territory as reinforcement for the pair bond. Pairs who twenty years earlier had been banded in the neighborhood of the old Pan-American hotel, Gooneyville Lodge, were still mated, still breeding. Attachment for the nest site went beyond explanation. Like all sea birds, the colonies disperse at the end of the breeding season to gather again the following year. While the birds are away at sea, as I have already mentioned, storms may erase all landmarks in the breeding area. Yet when Rice and Kenyon mapped the territories of 100 pairs, they found that only five in the succeeding season built their nests more than thirteen feet from the site of the previous season's nests. The average distance was little more than a yard. How did the birds know where last year's site had been?

It is the kind of question which cannot be answered but can at least be approached through the principles of population genetics. It is to the interest of the population that the propinquity of a breeding community be preserved. If we cannot yet understand the mechanics of natural selection's devices, we can at least understand what natural selection is up to. And just how far evolution is concerned with the population, to what lengths evolution may shrug at the fate of the individual, finds no more gruesome illustration than in the behavior of the Laysan albatross. Human sympathies may recoil, the United States Navy may have shuddered, but Rice and Kenyon recorded all.

The observers noticed first that if a nest with a chick should be moved more than six feet from a site, the parents would attend it for a day or two, then return to the site and leave the offspring uncared for. Then in February, 1957, the fundamental devotions of albatross life were exposed in grotesque severity. A new installation at the Navy base was being constructed. Crews went in to bulldoze the area. Under strict instructions to go easy on albatrosses, they moved 100 nests together with chicks distances of up to 100 yards from the site. The chicks huddled in the nests or dug new little nests of their own in the sand. The parents ignored them. Day after day they

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sat on the sidelines, watched the construction work, and waited for day to be done. With the five-o'clock whistle the crews would leave the gouged area and the parents would return to where their homes had once been. There they would spend the night until the morning whistle drove them away. All chicks died.

Shortly after Rice and Kenyon made their ultimate observation concerning albatross site attachment, the United States Navy made its ultimate decision that, whatever the cost, Midway Island's gooney birds must be transported so far away around the world that none would ever return. How far need it be? Kenyon took charge of the ultimate experiment, and Navy bombers were assigned to the project. Eighteen birds were captured, banded, and their plumage marked with distinctive dyes. They were crated, loaded into the waiting planes, dispatched. Four went off to Puget Sound on the northwestern coast of the continental United States. Others were deposited in Japan, in the Philippines, in the Marshall and Mariana Islands, on the island of Oahu in Hawaii.

If there was a sense of finality in the Navy's action, then it failed to impress Midway's eighteen expatriates. The fate of four remains unknown. But fourteen returned. It is true that a bird abandoned in the Philippines, far outside the range of the species, took a very long while returning -- thirty-two days. But he had 4120 statute miles to cover. The birds sent to Puget Sound, on the other hand, did very well. Two vanished. But the other two returned in ten days and twelve, having traversed 3120 miles of Pacific Ocean lacking a single island or other landmark between the mainland and Hawaii. Weather reports revealed that during the time of the journey a low-pressure area had prevailed. There had probably been advers winds and, for much of the journey, overcast skies pr: hibiting solar observation.

Hand in hand, science and the United States Navy surrendered. "We suggest that existing theories of bird navigation do not fully explain their homing behavior," wrote Kenyon and Rice at the end of their report.

5

Our failure to penetrate the wilderness of the homing problem must rest, one suspects, on some larger failure to

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comprehend the powers of animal perception. We have scored some conspicuous successes along this frontier. It has become common knowledge, for example, that a porpoise "sees" by means of echoes. Otherwise it- should be a secret as inscrutable as animal navigation itself how a porpoise, in water so muddy that he cannot see to the end of his own snout, can still find food in your hand and with all delicacy take it from you. It is less than common knowledge, perhaps, that a fish called Gymnarchus in an equally muddy African river like the Niger will stake out a territory around his nest and recognize and expel all intruders. How does he "see" them? Gymnarchus generates an electric field, swims in the middle of it, and has means of sensing any object intruding on the field. How he discriminates between legitimate enemies and his mate, whom he never attacks, remains a little obscure.

These, of course, are the kinds of sensory powers for which students of animal navigation have made such exhaustive searches to no end but the exhaustion of science. And so one must suspect that the homing power, like other inexplicable territorial powers, may rest on perceptions of a quite different order, and that until science accomplishes some major penetration into areas of perception at present unknown, we shall continue to grope through our own muddy waters. Whether perceptions of an extrasensory order exist, no layman can judge. Hints, not evidence, are all we have. Accidental encounters, not systematic investigations, have characterized the scientific approach to perceptions lying beyond the normal range of explicable senses. A few of those encounters, however, have given us hints of a sort.

In late 1965 the American journal Science published a short account of an unexplained relation between certain identical twins. The electroencephalogram is a commonly used device for measuring activity in the brain. A recognizable activity is known as an alpha rhythm, a peculiar wave set up in the absence of visual stimuli, as when one closes one's eyes. The twins tested in a Philadelphia laboratory were separated and placed in different rooms. In most cases nothing happened. But in two out of fifteen sets of twins a remarkable event left its record on the apparatus. Again and again, if one twin closed his eyes, thus setting up the alpha wave, the same wave would instantly appear in the brain of his twin in the next room.

142 THE TERRITORIAL IMPERATIVE

Protest is the normal posture of science when confronted by such observations, and the editors of Science received the predictable and perhaps justifiable bagful of protests to the alpha-wave report. But one must recall the strange and thoroughly inexplicable behavior of tilapia made by the Dutch ethologist G.-P. Baerends many years ago. These are the fish among which the intruder must be twice as big as the proprietor if the intruder is to succeed. When tilapia are young, however, they have not yet established territories and live in schools. At this age the fish are gray with dark horizontal stripes. And if a strange fish, no matter how small, is introduced to a tank of young tilapia, there will be the strangest of responses. All will instantly and simultaneously show vertical bars of marking. Baerends interpreted the response as anxiety, perhaps one of selective value providing camouflage in weedy waters. But all members respond at once, whether or not threatened by the invader, whether or not even within sight of it. How is the anxiety communicated within the school?

Neither the arguable alpha wave nor the inarguable vertical bars of the tilapia tell us anything about the homing of the Laysan albatross or the stimulation of energy in a man defending his hearth and home. But all suggest much about that vast green continent of knowledge, wild and almost untouched, which the new biology today faces. Population genetics informs us as to why natural selection, through a billion or two of developing years, may have encouraged the most subtle powers of alliance between the individual and the evolutionary unit of which he is a part. It now becomes the business of the scientist, in the interest of his species, to discover just what evolution has accomplished, and how it has done it. And let no layman rest content if a scientist here or there gives the great green continent a puzzled frown, and says, "What elephant?"

The territorial imperative shapes your way and mine to patterns larger and more immortal than ourselves. As we move on to explore the social territory, so significant in human life, we shall see that the patterns of value to man are of a different sort than those of value to homing animals. The adaptability of man and protoman has made unnecessary a periodic dispersal of our numbers about the seas or continents, and consigned to selective neglect any mechanism beyond homesickness to aid us on our return.

THE VOYAGE OF THE ANIMALS 143

Even so, we may glimpse in our nostalgias a shadow of that force compelling the voyages of animals.

The individual, whoever he may be, is not quite free to mate with whom he pleases. And so the homing creature, wherever he may be when the season comes around, finds nostalgia enfolding him. The seal will abandon her growing pup in warm California waters though she must swim across all the northern Pacific to reach the place where she was born. Gravid salmon, bulging with eggs, must navigate a thousand miles of blue water to reach the mouth of a certain river, must surmount rapids and waterfalls and pass the forks of a hundred streams, and must at last reach that certain stretch of fast-flowing brook, the only place on the watery earth where nature will permit her eggs to be fertilized.

So it is with the skua, treading the air of a stormy continent. So it is with the1 barred warbler, deserting an African feeding ground to die, perhaps, in some late northern blizzard. So it is with geese as we see them tall in a springtime sky traveling in their imperishable Vs toward a faraway, finite tract of marsh, remarkable only to the eyes of a goose, in a featureless Canadian plain. Devotion to home-place commands the sorting of animate beings, of gulls and shearwaters and returning soldiers, so that species shall not vanish in a chaos of genetical debris.

The portrait of life being painted by the new biology bears small resemblance to that natural world of anarchistic instinct and relentless self-interest which depressed a Tennyson, inspired a Freud, perturbed a Darwin, and confused a century. It is a world of order and ordained self-sacrifice to greater and longer goods; it is an ordered world in which territory, I maintain, exerts a prime moral force; and it is a world -- we must remind ourselves again and again -- to which we belong. Should all this be so, and should a little piece of sovereign earth or air or water provide indeed such a key to the locks of animate necessity, then I myself can little wonder that evolution has equipped us with not only the key but an almighty urge to defend it.