offspring is chiefly the mechanical tangling of the young animal’s
tiny claws in the long maternal fur. I have taken away a young sloth
and hooked it to a branch five feet away. Being hungry it began at
once to utter its high, penetrating penny whistle. To no other sound,
high or low, with even a half tone’s difference does the sloth pay any
heed, but its dim hearing is attuned to just this vibration. Slowly the
mother starts off in what she thinks is the direction of the sound. It
is the moment of moments in the life of the young animal. Yet I have
seen her again and again on different occasions pass within two feet
of the little chap, and never look to right or left, but keep straight
on, stolidly and unvaryingly to the high jungle, while her baby, a few
inches out of her path, called in vain. No kidnapped child hidden in
mountain fastness or urban underworld was ever more completely lost
to its parent than this infant, in full view and separated by only a
sloth’s length of space.
A gun fired close to the ear of a sloth will usually arouse not the
slightest tremor; no scent of flower or acid or carrion causes any
reaction; a sleeping sloth may be shaken violently without awakening,
the waving of a scarlet rag, or a climbing serpent a few feet away
brings no gleam of curiosity or fear to the dull eyes; an astonishingly
long immersion in water produces discomfort but not death. When we
think what a constant struggle life is to most creatures, even when
they are equipped with the keenest of senses and powerful means of
offense, it seems incredible that a sloth can hold its own in this
overcrowded tropical jungle.
From birth to death it climbs slowly about the great trees, leisurely
feeding, languidly loving, and almost mechanically caring for its
young. On the ground a host of enemies await it, but among the higher
branches it fears chiefly occasional great boas, climbing jaguars and,
worst of all, the mighty talons of harpy eagles. Its means of offense
is a joke--a slow, ineffective reaching forward with open jaws, a
lethargic stroke of arm and claws which anything but another sloth can
avoid. Yet the race of sloths persists and thrives, and in past years I
have had as many as eighteen under observation at one time.
A sloth makes no nest or shelter; it even disdains the protection
of dense foliage. But for all its apparent helplessness it has
a _cheval-de-frise_ of protection which many animals far above
it in intelligence might well envy. Its outer line of defense is
invisibility--and there is none better, for until you have seen your
intended prey you can neither attack nor devour him. No hedgehog
or armadillo ever rolled a more perfect ball of itself than does a
sloth, sitting in a lofty, swaying crotch with head and feet and
legs all gathered close together inside. This posture, to an
onlooker, destroys all thought of a living animal, but presents a very
satisfactory white ants’ nest or bunch of dead leaves. If we look at
the hair of a sloth we will see small, grey patches along the length of
the hairs--at first sight bits of bark and débris of wood. But these
minute, scattered particles are of the utmost aid to this invisibility.
They are a peculiar species of alga or lichen-like growth which is
found only in this peculiar haunt, and when the rains begin and all the
jungle turns a deep, glowing emerald, these tiny plants also react to
the welcome moisture and become verdant--thus throwing over the sloth a
protecting, misty veil of green.
Even we dull-sensed humans require neither sight nor hearing to detect
the presence of an animal like the skunk; in the absolute quiet and
blackness of midnight we can tell when a porcupine has crossed our
path, or when there are mice in the bureau drawers. But a dozen sloths
may be hanging to the trees near at hand and never the slightest whiff
of odor comes from them. A baby sloth has not even a baby smell, and
all this is part of the cloak of invisibility. The voice, raised
so very seldom, is so ventriloquil, and possesses such a strange,
unanimal-like quality that it can never be a guide to the location much
less to the identity of the author. Here we have three senses, sight,
hearing, smell, all operating at a distance, two of them by vibrations,
and all leagued together to shelter the sloth from attack.
But in spite of this dramatic guard of invisibility the keen eyes of
an eagle, the lapping tongue of a giant boa, and the amazing delicacy
of a jaguar’s sense of smell break through at times. The jaguar scents
sign under the tree of the sloth, climbs eagerly as far as he dares
and finds ready to his paw the ball of animal unconsciousness; a harpy
eagle half a mile above the jungle sees a bunch of leaves reach out
a sleepy arm and scratch itself--something clumps of leaves should
not do. Down spirals the great bird, slowly, majestically, knowing
there is no need of haste, and alights close by the mammalian sphere.
Still the sloth does not move, apparently waiting for what fate may
bring--waiting with that patience and resignation which comes only
to those of our fellow creatures who cannot say, “I am I!” It seems
as if Nature had deserted her jungle changeling, stripped now of its
protecting cloak.
The sloth however has never been given credit for its powers of passive
resistance, and now, with its enemy within striking distance, its
death or even injury is far from a certainty. The crotch which the
sloth chooses for its favorite outdoor sport, sleep, is unusually
high up or far out among the lesser branches, where the eight claws
of the eagle or the eighteen of a jaguar find but precarious hold. In
order to strike at the quiescent animal the bird has to relinquish
half of its foothold, the cat nearly one quarter. If the victim were
a feathery bush turkey or a soft-bodied squirrel, one stroke would be
sufficient, but this strange creature is something far different. In
the first place it is only to be plucked from its perch by the exertion
of enormous strength. No man can seize a sloth by the long hair of the
back and pull it off. So strong are its muscles, so vise-like the grip
of its dozen talons that either the crotch must be cut or broken off or
the long claws unfastened one by one. Neither of these alternatives is
possible to the attacking cat or eagle. They must depend upon crushing
or penetrating power of stroke or grasp.
Here is where the sloth’s second line of defense becomes operative.
First, as I have mentioned, the swaying branch and dizzy height is in
his favor, as well as his immovable grip. To begin with the innermost
defenses, while his jungle fellows, the ring-tailed and red howling
monkeys, have thirteen ribs, the sloth may have as many as twenty; in
the latter animal they are, in addition, unusually broad and flat,
slats rather than rods. Next comes the skin which is so thick and tough
that many an Indian’s arrow falls back without even scratching the
hide. The skin of the unborn sloth is as tough and strong as that of
a full-grown monkey. Finally we have the fur--two distinct coats, the
under one fine, short and matted, the outer long, harsh and coarse. Is
it any wonder that, teetering on a swaying branch, many a jaguar has
had to give up after frantic attempts to strike his claws through the
felted hair, the tough skin and the bony lattice-work which protect the
vitals of this Edentate bur!
Having rescued our sloth from his most immediate peril let us watch
him solve some of the very few problems which life presents to
him. Although the cecropia tree, on the leaves of which he feeds,
is scattered far and wide through the jungle, yet sloths are found
almost exclusively along river banks, and, most amazingly, they
not infrequently take to the water. I have caught a dozen sloths
swimming rivers a mile or more in width. Judging from the speed of
short distances, a sloth can swim a mile in three hours and twenty
minutes. Their thick skin and fur must be a protection against
crocodiles, electric eels and perai fish as well as jaguars. Why they
should ever wish to swim across these wide expanses of water is as
inexplicable as the migration of butterflies. One side of the river
has as many comfortable crotches, as many millions of cecropia leaves
and as many eligible lady sloths as the other! In this unreasonable
desire for anything which is out of reach sloths come very close to a
characteristic of human beings.
Even in the jungle sloths are not always the static creatures which
their vegetable-like life would lead us to believe, as I was able to
prove many years ago. A young male was brought in by Indians and after
keeping it a few days I shaved off two patches of hair from the center
of the back, and labelling it with a metal tag I turned it loose.
Forty-eight days later it was captured near a small settlement of
bovianders several miles farther up and across the river. During this
time it must have traversed four miles of jungle and one of river.
The principal difference between the male and female three-toed
sloths is the presence on the back of the male of a large, oval spot
of orange-colored fur. To any creature of more active mentality such
a minor distinction must often be embarrassing. In an approaching
sloth, walking upside-down as usual, this mark is quite invisible,
and hence every meeting of two sloths must contain much of delightful
uncertainty, of ignorance whether the encounter presages courtship or
merely gossip. But color or markings have no meaning in the dull eyes
of these animals. Until they have sniffed and almost touched noses they
show no recognition or reaction whatever.
I once invented a sloth island--a large circle of ground surrounded by
a deep ditch, where sloths climbed about some saplings and ate, but
principally slept, and lived for months at a time. This was within
sight of my laboratory table, so I could watch what was taking place by
merely raising my head. Some of the occurrences were almost too strange
for creatures of this earth. I watched two courtships, each resulting
in nothing more serious than my own amusement. A female was asleep
in a low crotch, curled up into a perfect ball deep within which was
ensconced a month-old baby. Two yards overhead was a male who had slept
for nine hours without interruption. Moved by what, to a sloth, must
have been a burst of uncontrollable emotion, he slowly unwound himself
and clambered downward. When close to the sleeping beauty he reached
out a claw and tentatively touched a shoulder. Even more deliberately
she excavated her head and long neck and peered in every direction but
the right one. At last she perceived her suitor and looked away as if
the sight was too much for her. Again he touched her post-like neck,
and now there arose all the flaming fury of a mother at the flirtatious
advances of this stranger. With incredible slowness and effort she
freed an arm, deliberately drew it back and then began a slow forward
stroke with arm and claws. Meanwhile her gentleman friend had changed
his position so the blow swept, or, more correctly passed, through
empty air, the lack of impact almost throwing her out of the crotch.
The disdained one left with slowness and dignity--or had he already
forgotten why he had descended?--and returned to his perch and slumber,
where I am sure, not even such active things as dreams came to disturb
his peace.
The second courtship advanced to the stage where the Gallant actually
got his claws tangled in the lady’s back hair before she awoke. When
she grasped the situation she left at once and clambered to the highest
branch tip followed by the male. Then she turned and climbed down and
across her annoyer, leaving him stranded on the lofty branch looking
eagerly about and reaching out hopefully toward a big, green iguana
asleep on the next limb in mistake for his fair companion. For an hour
he wandered languidly after her, then gave it up and went to sleep.
Throughout these and other emotional crises no sound is ever uttered,
no feature altered from its stolid repose. The head moves mechanically
and the dull eyes blink slowly, as if striving to pierce the opaque
veil which ever hangs between the brain of a sloth and the sights,
sounds and odors of this tropical world. If the orange back spot was
ever of any use in courtship, in arousing any emotion æsthetic or
otherwise, it must have been in ages long past when the ancestors of
sloths, contemporaries of their gigantic relatives the Mylodons, had
better eyesight for escaping from sabre-toothed tigers, than there is
need today.
The climax of a sloth’s emotion has nothing to do with the opposite sex
or with the young, but is exhibited when two females are confined in a
cage together. The result is wholly unexpected. After sniffing at one
another for a moment, they engage in a slowed-up moving-picture battle.
Before any harm is done one or the other gives utterance to the usual
piercing whistle and surrenders. She lies flat on the cage floor and
offers no defense while the second female proceeds to claw her, now and
then attempting, usually vainly, to bite. It is so unpleasant that I
have always separated them at this stage, but there is no doubt that
in every case the unnatural affray would go on until the victim was
killed. In fact I have heard of several instances where this actually
took place.
A far pleasanter sight is the young sloth, one of the most adorable
balls of fuzzy fur imaginable. While the sense of play is all but
lacking his trustfulness and helplessness are most infantile. Every
person who takes him up is an accepted substitute for his mother and
he will clamber slowly about one’s clothing for hours in supreme
contentment. One thing I can never explain is that on the ground the
baby is even more helpless than his parents. While they can hitch
themselves along, body dragging, limbs outspread, until they reach the
nearest tree, a young sloth is wholly without power to move. Placed on
a flat bit of ground it rolls and tumbles about, occasionally greatly
encouraged by seizing hold of its own foot or leg under the impression
that at last it has encountered a branch.
Sloths sleep about twice as much as other mammals and a baby sloth
often gets tired of being confined in the heart of its mother’s
sleeping sphere, and creeping out under her arm will go on an exploring
expedition around and around her. When over two weeks old it has
strength to rise on its hind legs and sway back and forth like nothing
else in the world. Its eyes are only a little keener than those of the
parent and it peers up at the foliage overhead with the most pitiful
interest. It is slowly weaned from a milk diet to the leaves of the
cecropia which the mother at first chews up for her offspring.
I once watched a young sloth about a month old and saw it leave its
mother for the first time. As the old one moved slowly back and forth,
pulling down cecropia leaves and feeding on them, the youngster took
firm grip on a leaf stem, mumbling at it with no success whatever.
When finally it stretched around and found no soft fur within reach it
set up a wail which drew the attention of the mother at once. Still
clinging to her perch, she reached out a forearm to an unbelievable
distance and gently hooked the great claws about the huddled infant,
which at once climbed down the long bridge and tumbled headlong into
the hollow awaiting it.
When a very young sloth is gently disentangled from its mother and
hooked on to a branch something of the greatest interest happens.
Instead of walking forward, one foot after the other, and upside-down
as all adult sloths do, it reaches up and tries to get first one
arm then the other _over_ the support, and to pull itself into an
upright position. This would seem to be a reversion to a time--perhaps
millions of years ago--when the ancestors of sloths had not yet
begun to hang inverted from the branches. After an interval of clumsy
reaching and wriggling about, the baby by accident grasps its own body
or limb, and, in this case, convinced that it is at last anchored
safely again to its mother, it confidently lets go with all its other
claws and tumbles ignominiously to the ground.
The moment a baby sloth dies and slips from its grip on the mother’s
fur, it ceases to exist for her. If it could call out she would reach
down an arm and hook it toward her, but simply dropping silently means
no more than if a disentangled bur had fallen from her coat. I have
watched such a sloth carefully and have never seen any search of her
own body or of the surrounding branches, or a moment’s distraction from
sleep or food. An imitation of the cry of the dead baby will attract
her attention, but if not repeated she forgets it at once.
It is interesting to know of the lives of such beings as this--chronic
pacifists, normal morons, the superlative of negative natures, yet
holding their own amidst the struggle for existence. Nothing else
desires to feed on such coarse fodder, no other creature disputes
with it the domain of the under side of branches, hence there is no
competition. From our human point of view sloths are degenerate;
from another angle they are among the most exquisitely adapted of
living beings. If we humans, together with our brains, fitted as well
into the possibilities of our own lives we should be infinitely finer
and happier,--and, besides, I should then be able to interpret more
intelligently the life and the philosophy of sloths!
VI
MANGROVE MYSTERY
One day I found a hammock-form of roots, a maze of gentle curves
which gave and braced, and, taking paper, looked to see if a mangrove
had anything of interest to offer. At the end of three hours I slid
painfully down into the rising tide, my unpenciled sheet fluttered off,
and I went away with my mind in a whirl.
I rejoiced in Barnum’s Circus long before I learned to write, but, if
the first time thereafter, my mother had given me pencil and notebook
with instructions to describe everything that took place in all
three rings and on the stage, as well as the freaks, side shows and
menagerie, my ideas would have been of equal clarity and inclusiveness
as at my first mangrove séance. Above, around, beneath were interlacing
trapezes, flying rings and rope ladders, liana nets and gaily painted
poles, waving banners of emerald strung along the rafters, and high
over all the canvas of the sky. And everywhere the performers--acrobats
and leapers--worked mighty feats of balance and of strength; whiffs
arose of strange and unknown creatures; thrilling, tuning-up squeaks
and umpahs came from hidden orchestras which surely soon must burst
forth in full fanfare of breath-shortening music. Now and then a being
would creep slowly past, (doubtless on his weary way to a long parade
about some invisible arena), of such sight and form, that if raised to
man’s height would be a side show in himself.
But even at the first confusing survey, the mangrove stood out vivid
and clear-cut. It had the aspect of a god, an Atlas, with feet firm
planted upon earth, regardless whether currents of water or winds of
air swirled about its knees, and with wide arms out--upward spread
to the sky, upon which thousands of weaker beings found sanctuary.
Some alighted for temporary rest of weary wings, others for longer
periods, day boarders who came for meals or season residents who built
their houses and reared their families upon the vibrant roots. And
finally were those who knew no other world or scene, but, born or
hatched upon the mangroves, clung to them until loosed by death. By
their little body dropping to the water, they paid their final debt
to Gravitation, returning to his implacable coffers this small meed
of elevation-energy, which by grip of tendrils or of fingers they had
possessed throughout their lives.
[Illustration: “In the sunshine and warmth of the mangrove tangle”]
These were all kindly, or at most indifferent folk, who if they gave
nothing of value, did no harm. In a circus, the smiling faces of two
acrobats who catch one another in midair may mask bitter hatred, a
desire to swing short, or grip loosely; the story writers are fond of
showing us the tragic sorrow obverse of the clown’s grinning visage.
In the sunshine and warmth of the mangrove tangle, behind the swaying
leaves and bee-beckoning blossoms’ fragrance is terrible strife and
slow death. The splendid plant gives shelter and support upon its
sturdy uplifted arms, not only to the fairy homes of humming-birds,
but to parasites whose gratitude is never to cease strangling with
inflexible coils, or, more insidiously, gently to insert living threads
of death into the very heart of their supporter. Out of all this,
how futile it seems to try to give any real idea of the marvel of
mangrove life. At most we can hope only to arouse a worthy discontent,
a disquieting desire also to go and see. For here are living tales,
complete but as yet unworded, worthy to fill volumes of Carroll or
Dunsany or Barrie or Blackwood; here are scenes needing only paper
tracing to equal the best of Rackham or Sime, to touch the emotional
gamut of Böcklin and Heath Robinson.
About ten thousand years before I filled this fountain pen, some
ancestor of yours and mine--our “touch of nature”--discovered that
by building a house of piles out in a lake, he could thwart the wild
animals which ever threatened him, and lessen the danger of a surprise
attack from equally-to-be-dreaded envious or hasty-tempered neighbors.
Few carnivores care to swim after their prey, and war canoes had hardly
been invented. Such sanctuaries gave to families and to small tribes
time to think, to invent new weapons, to seize new opportunities and to
take better care of their babies.
Today, while pushing a canoe through the roots of the mangrove jungle,
I thought enthusiastically of my pile-dwelling ancestors as I noted
many exciting similes, and then paddled hastily back to the laboratory
to see what botanists had thought about it. I found much of interest,
but my mind was sobered, my imagination quieted. There was nothing of
Swiss lake dwellings, but a very definite title of _Rhizophora Mangle_,
and a casual remark of branches being supported by simple, vertical
roots; it was put down that the petals were lacerate-woolly on the
margin, exceeded by the calyx limb; but their delicate odor was passed
by without comment; the living shifts of greens on the foliage, with
the veins carrying shafts of parrot color over the background of pale
chrysolite--this was ignored; to the botanist the leaves were leathery,
quite entire, obovate-lanceolate and blunt--a statement unquestionably
to the point. Finally I learned that the astringent bark is employed
for tanning, and I returned to my living mangroves, alias R. Mangle,
wondering if too constant pondering upon astringent, unadulterated
facts is not often efficacious in a sort of mental tanning. Our
mangrove might yield a new harvest to us if we could choose a different
contact of thought, clothing the fruit with the vital interest hidden
in “one-seeded by abortion,” and yet avoiding sentimental pleonasms.
However we decide to think of this plant, it is sure to be with
admiration, for it stands out as a pioneer. Among earthly vegetation
the mangrove is an aristocrat, a true dicotyledon, but it has dared
to seek again the watery habitat of the lowlier growths, indeed of
the very green algæ from which land plants originally developed. Like
the penguin which has relinquished the ærial wing for an aquatic
fin, or the seal which has encased its five fingers and five toes in
flipper mittens, so the mangrove, while retaining all its badges of
aristocracy, has returned to the haunts of the ancestors of all plants,
from whence it can look calmly shoreward at the terrible struggle for
life a few feet away, where every inch of soil is battled for, where
the vigorous monopolize air and sunlight.
Such a radical change cannot be achieved without far-reaching
adaptations and readjustments; the banker does not become a farmer
merely by moving to the country, and every part of a mangrove shows
delicate modes of meeting the strange new conditions as cunningly as
the shift of muscles of a jiu-jitsu wrestler encountering an unknown
opponent.