DWELLINGS.
ANIMALS NATURALLY PROVIDED WITH DWELLINGS--ANIMALS WHO
INCREASE THEIR NATURAL PROTECTION BY THE ADDITION OF FOREIGN
BODIES--ANIMALS WHO ESTABLISH THEIR HOME IN THE NATURAL OR
ARTIFICIAL DWELLINGS OF OTHERS--CLASSIFICATION OF ARTIFICIAL
SHELTERS--HOLLOWED DWELLINGS--RUDIMENTARY
BURROWS--CAREFULLY-DISPOSED BURROWS--BURROWS WITH BARNS
ADJOINED--DWELLINGS HOLLOWED OUT IN WOOD--WOVEN
DWELLINGS--RUDIMENTS OF THIS INDUSTRY--DWELLINGS FORMED OF
COARSELY-ENTANGLED MATERIALS--DWELLINGS WOVEN OF FLEXIBLE
SUBSTANCES--DWELLINGS WOVEN WITH GREATER ART--THE ART OF
SEWING AMONG BIRDS--MODIFICATIONS OF DWELLINGS ACCORDING TO
SEASON AND CLIMATE--BUILT DWELLINGS--PAPER NESTS--GELATINE
NESTS--CONSTRUCTIONS BUILT OF EARTH--SOLITARY MASONS--MASONS
WORKING IN ASSOCIATION--INDIVIDUAL SKILL AND
REFLECTION--DWELLINGS BUILT OF HARD MATERIALS UNITED BY
MORTAR--THE DAMS OF BEAVERS.
Animals construct dwellings either to protect themselves from the
cold, heat, rain, and other chances of the weather, or to retire to at
moments when the search for food does not compel them to be outside
and exposed to the attacks of enemies. Some inhabit these refuges
permanently; others only remain there during the winter; others,
again, who live during the rest of the year in the open air set up
dwellings to bring forth their young, or to lay their eggs and rear
the offspring. Whatever the object may be for which these retreats are
built, they constitute altogether various manifestations of the same
industry, and I will class them, not according to the uses which they
are to serve, but according to the amount of art displayed by the
architect.
In this series, as in those which we have already studied, we shall
find every stage from that of beings provided for by nature, and
endowed with a special organ which secretes for them a shelter, up to
those who are constrained by necessity to seek in their own
intelligence an expedient to repair the forgetfulness of nature. These
productions, so different in their origin, can only be compared from
the point of view of the part they play; there are analogies between
them but not the least homology.
_Animals naturally provided with dwellings._--Nearly all the Mollusca
are enveloped by a very hard calcareous case, secreted by their
mantle: this shell, which is a movable house, they bear about with
them and retire into at the slightest warning.
Caterpillars which are about to be transformed into chrysalides weave
a cocoon, a very close dwelling in which they can go through their
metamorphosis far from exterior troubles. It is an organic form of
dwelling, or produced by an organ. It is not necessary to multiply
examples of this kind; they are extremely numerous. In the same
category must be ranged the cells issuing from the wax-glands which
supply Bees with materials for their combs in which they enclose the
eggs of the queen with a provision of honey.
I do not wish to insist on creations of this kind which are
independent of the animal's will and reflection. Near these facts must
be placed those in which animals, still using a natural secretion, yet
endeavour to obtain ingenious advantages from it unknown by related
species.
[Illustration: FIG. 18.]
There is, for example, the _Macropus viridi-auratus_, or
Paradise-fish, which blows air bubbles in the mucus produced from its
mouth. This mucus becomes fairly resistant, and all the bubbles
imprisoned and sticking aside by side at last form a floor. It is
beneath this floating shelter that the fish suspends its eggs for its
little ones to undergo their early development.
_Animals who increase their natural protection by the addition of
foreign bodies._--Certain tubicolar Annelids, whose skin furnishes
abundant mucus which does not become sufficiently hard to form an
efficacious protection, utilise it to weld together and unite around
them neighbouring substances, grains of sand, fragments of shell, etc.
They thus construct a case which both resembles formations by special
organs and manufacture by the aid of foreign materials. The larvae of
_Phryganea_, who lead an aquatic life, use this method to separate
themselves from the world and prepare tubes in which to dwell. (Fig.
18.) All the fragments carried down by the stream are good for their
labours on condition only that they are denser than the water. They
take possession of fragments of aquatic leaves, and little fragments
of wood which have been sufficiently long in the water to have
thoroughly imbibed it and so become heavy enough to keep themselves at
the bottom, or at least to prevent them from floating to the surface.
It is the larva of _Phryganea striata_ which has been best studied;
those of neighbouring species evidently act much in the same way, with
differences only in detail. The little carpenter stops a fragment
rather longer than his own body, lies on it and brings it in contact
with other pieces along his own sides. He thus obtains the skeleton of
a cylinder. The largest holes are filled up with detritus of all
kinds. Then these materials are agglutinated by a special secretion.
The larva overlays the interior of its tube with a covering of soft
silk which renders the cylinder watertight and consolidates the
earlier labours. The insect is thus in possession of a safe retreat.
Resembling some piece of rubbish, it completes its metamorphosis in
peace, undisturbed by the carnivora of the stream. There is here
already a tendency towards the dwellings of which I shall speak later
on, and which are entirely formed of the external environment.
_Animals who establish their home in the natural or artificial
dwellings of others._--Between the beings whom nature has endowed with
a shelter and those who construct it by their own industry, we may
intercept those who, deprived of a natural asylum and not having the
inclination or the power to make one, utilise the dwellings of others,
either when the latter still inhabit them, or when they are empty on
account of the death or departure of the owner. In the natural
sciences there is no group of facts around which may be traced a clear
boundary; each of them is more or less closely related to a group
which appears at first of an entirely different nature. Thus it does
not enter into our plan to speak of parasites. Yet, if among these
some turn to a host to demand of him both food and shelter, if even
they can come to be so modified and so marked by parasitism that they
can live in no other way, there are others who ask for lodging only
from an animal better protected than they are themselves. It is these
whose customs we are called upon to consider. In the interior of the
branchial chamber of many bivalvular Mollusca, and especially the
Mussel, there lives a little crustaceous commensal called the Pea-crab
(_Pinnoteres pisum_). He goes, comes, hunts, and retires at the least
alarm within his host's shell. The mussel, as the price of its
hospitality, no doubt profits by the prizes which fall to the little
crab's claws. It is even said that the crab in recognition of the
benefits bestowed by his indolent friend keeps him acquainted with
what is passing on around, and as he is much more active and alert
than his companion he sees danger much farther away, and gives notice
of it, asking for the door to be shut by lightly pinching the mussel's
gill. But this gratitude of the Crustacean towards a sympathetic
bivalve is merely a hypothesis; we do not exactly know what passes in
the intimacy of these two widely-differing natures.
For birds like the Cuckoo and the _Molothrus_ it is not possible to
plead attenuating circumstances. They occupy a place in an inhabited
house without paying any sort of rent. Every one knows the Cuckoo's
audacity. The female lays her eggs in different nests and troubles
herself no further about their fate. She seeks for her offspring a
shelter which she does not take the trouble to construct, and moreover
at the same time assures for them the cares of a stranger in place of
her own.
In North America a kind of Starling, the _Molothrus pecoris_, commonly
called the Cow-bird, acts in the same careless fashion. It lives in
the midst of herds, and owes its specific name to this custom; it
feeds on the parasites on the skin of cattle. This bird constructs no
nest. At the moment of laying the female seeks out an inhabited
dwelling, and when the owner is absent she furtively lays an egg
there. The young intruder breaks his shell after four days'
incubation, that is to say, usually much before the legitimate
children; and the parents, in order to silence the beak of the
stranger who, without shame, claims his share with loud cries, neglect
their own brood which have not yet appeared, and which they abandon.
Their foster children repay them, however, with the blackest
ingratitude. As soon as the little _Molothrus_ feels his body covered
with feathers and his little wings strong enough to sustain him he
quits his adopted parents without consideration. These birds show a
love of independence very rare among animals, with whom conjugal
fidelity has become proverbial; they do not unite in couples; unions
are free, and the mother hastens to deliver herself from the cares of
bringing up her young in the manner we have seen. Two other species of
_Molothrus_ have the same habit, as have the American Cuckoo and the
Golden Cuckoo of South Africa.
The habits of the _Molothrus bovariensis_, a closely allied Argentine
Cow-bird, have been carefully studied by Mr. W. H. Hudson, who has
also some interesting remarks as to the vestiges of the nesting
instinct in this interesting parasitical bird, which now is constantly
dropping eggs in all sorts of places, even on the ground, most of them
being lost. "Before and during the breeding-season the females,
sometimes accompanied by the males, are seen continually haunting and
examining the domed nests of the _Dendrocolaptidae_. This does not seem
like a mere freak of curiosity, but their persistence in their
investigations is precisely like that of birds that habitually make
choice of such breeding-places. It is surprising that they never do
actually lay in such nests, except when the side or dome has been
accidentally broken enough to admit the light into the interior.
Whenever I set boxes up in my trees, the female Cow-birds were the
first to visit them. Sometimes one will spend half a day loitering
about and inspecting a box, repeatedly climbing round and over it, and
always ending at the entrance, into which she peers curiously, and
when about to enter starting back, as if scared at the obscurity
within. But after retiring a little space she will return again and
again, as if fascinated by the comfort and security of such an abode.
It is amusing to see how pertinaciously they hang about the ovens of
the Oven-birds, apparently determined to take possession of them,
flying back after a hundred repulses, and yet not entering them even
when they have the opportunity. Sometimes one is seen following a Wren
or a Swallow to its nest beneath the eaves, and then clinging to the
wall beneath the hole into which it disappeared. That it is a
recurrence to a long-disused habit I can scarcely doubt. I may mention
that twice I have seen birds of this species attempting to build
nests, and that on both occasions they failed to complete the work. So
universal is the nest-making instinct that one might safely say the
_M. bovariensis_ had once possessed it, and that in the cases I have
mentioned it was a recurrence, too weak to be efficient, to the
ancestral habit." Mr. Hudson suggests that this bird lost the
nest-making instinct by acquiring the semi-parasitical habit, common
to many South American birds, of breeding in the large covered nests
of the _Dendrocolaptidae_, although, owing to increased severity in the
struggle for the possession of such nests, this habit was
defeated.[81]
[81] P. L. Sclater and W. H. Hudson, _Argentine
Ornithology_, 1888, vol. i. pp. 72-86. A brief summary of
the facts regarding parasitism among birds will be found in
Girod's _Les Societes chez les Animaux_, 1891, pp.
287-294.
The _Rhodius anarus_, a fish of European rivers, also ensures a quiet
retreat for his offspring by a method which is not less indiscreet. At
the period of spawning, a male chooses a female companion and with
great vigilance keeps off all those who wish to approach her. When the
laying becomes imminent, the _Rhodius_, swimming up and down at the
bottom of the stream, at length discovers a _Unio_. The bivalve is
asleep with his shell ajar, not suspecting the plot which is being
formed against him. It is a question of nothing less than of
transforming him into furnished lodgings. The female fish bears
underneath her tail a prolongation of the oviduct; she introduces it
delicately between the Mollusc's valves and allows an egg to fall
between his branchial folds. In his turn the male approaches, shakes
himself over it, and fertilises it. Then the couple depart in search
of another _Unio_, to whom to confide another representative of the
race. The egg, well sheltered against dangers from without, undergoes
development, and one fine day the little fish emerges and frisks away
from his peaceful retreat.
Other animals, more respectful of property, avoid using another's
dwelling until it is abandoned by its proprietor, and no reproach of
indelicacy can be addressed to the _Gobius minutus_, a fish which
lives on our coasts at the mouth of rivers. The female lays beneath
overturned shells, remains of Oysters, or Cardium shells. The valve is
buried beneath several centimetres of sand, which supports it like a
vault. It forms a solid roof, beneath which the eggs undergo their
evolution. Sometimes the male remains by the little chamber to watch
over their fate. It is possible to distinguish the two holes of
entrance and exit which mark his habitual passage.
[Illustration: FIG. 19.]
The Hermit-crab perhaps knows best how to take advantage of old
clothes. (Fig. 19.) He collects shells of Gasteropods, abandoned
flotsam, the first inhabitant of which has died. The Hermit-crab
(_Pagurus Bernhardus_) is a Decapod Crustacean--that is to say, he
resembles a very small Crab. But his inveterate habit during so many
generations of sheltering his abdomen in a shell prevents this part
from being encrusted with lime and becoming hard. The legs and the
head remain in the ordinary condition outside the house, and the
animal moves bearing it everywhere with him; on the least warning he
retires into it entirely. But the Crustacean grows. When young he had
chosen a small shell. A Mollusc, in growing, makes his house grow with
him. The Hermit-crab cannot do this, and when his dwelling has become
too narrow he abandons it for one that is more comfortable. At first
enclosed in the remains of a _Trochus_, he changes into that of a
_Purpura_; a little later he seeks asylum in a Whelk. Beside the
shelter which these shells assure to the Crustacean, they serve to
mask his ferocity, and the prey which approaches confidently what it
takes to be an inoffensive Mollusc, becomes his victim.
The Great Horned Owl likewise does not construct a nest; but takes
possession of the dwellings abandoned by others. These birds utilise
for laying their eggs sometimes the nest of a Crow or a Dove,
sometimes the lair which a Squirrel had considered too dilapidated.
The female, without troubling about the bad state of these ruins, or
taking pains to repair them, lays her eggs here and sits on them.
_Classification of artificial shelters._--It is time to turn to
animals who have more regard for comfort, and who erect dwellings for
themselves or their offspring. These dwellings may be divided into
three groups: (1) Those which are hollowed in earth or in wood; (2)
those which in the simplest form result from the division of material
of any kind; then, as a complication, of materials bound together;
then, as a last refinement, of delicate materials, such as blades of
grass or threads of wool woven together; such are the nests of certain
birds and the tents of nomads; (3) those which are built of moist
earth which becomes hard on drying; the perfection of this method
consists of piling up hard fragments, pieces of wood or ashlar, the
moist earth being only a mortar which unites the hard parts together.
Animals exercise with varying success these different methods, all of
which Man still practises.
_Hollowed dwellings--Rudimentary burrows._--We will first occupy
ourselves with the dwelling hollowed in the earth. It is the least
complicated form. The number of creatures who purely and simply bury
themselves thus to obtain shelter is incalculable; I will only mention
a few examples, and pass on from simple combinations to the more
perfected industries, of which they present the first sketch.
It is known that at a certain epoch of the year Crabs abandon their
hard carapaces. This phenomenon is known by the name of the moult;
they remain in this condition for some time; it is the period during
which they grow; then their integuments are encrusted anew with lime
and again become resistant. While they are thus deprived of their
ordinary protection they are exposed to a crowd of dangers, and they
are so well aware of this that they remain hidden beneath rocks and
pebbles. A crab of Guadeloupe, called _Gecarinus ruricola_, escapes
the perils of this situation, thanks to its kind of life and its habit
of hollowing out a burrow to live in while it is deprived of its
habitual defence. This Crustacean lives on the earth, at a distance of
about ten or twelve kilometres from the sea-shore, and nourishes
itself on animal and vegetable remains. It approaches the water only
at the period of laying eggs, turning towards the coast in the months
of February and March. This migration does not take place, like some
others, in compact bands; each follows the road in independence, and
preserves a certain amount of liberty with regard to the path and the
epoch of the journey. They lead an aquatic life till May or June; then
the female abandons her little ones, who had begun their development
attached to her claws, and they return to land. The moult takes place
in August. At the approach of this dreaded crisis each hollows a hole
between two roots, supplies it with green leaves, and carefully stops
up the entrance. These labours accomplished, the crab is entirely
sheltered; it undergoes the moult in safety, and does not emerge from
its retreat until it is again capable of facing enemies, and of
seizing food with its claws, which have become hard again. This
seclusion appears to last a month. Here is, then, an example of a
temporary dwelling rendered necessary by special conditions of defect
for external life. We are here still in the infancy of the art.
Speaking generally, birds are accomplished architects. Certain of them
are, however, content with a rudimentary cavern. There is no question
here of those who retire to clefts in the rock or in trunks of trees,
for in these cases the cavity is only the support of the true house,
and it is in the construction of this that the artist reveals his
talent. I wish to speak of animals which remain in a burrow without
making a nest there. A Parroquet of New Zealand called the _Kakapo_
(_Strigops habroptilus_) thus dwells in natural or hollowed
excavations. It is only found in a restricted portion of the island
and leads a miserable life there, habitually staying in the earth and
pursued by numerous enemies, especially half-wild dogs. It tries to
hold its own, but its wings and beak do not suffice to protect it, and
the race would have completely disappeared if these birds were not
able to resist, owing to the prudence with which they stay within
their dwellings. They profit by a natural retreat, or one constructed
in rocks or beneath roots of trees; they only come out when impelled
by hunger, and return as soon as they can in case of danger.
A large number of animals also hollow out shelters for their eggs,
with the double object of maintaining them at a constant temperature
and of concealing them. Most reptiles act in this manner. The way in
which a Tortoise, the _Cistudo lunaria_, prepares its nest is
extremely curious. When the time for this labour arrives, the tortoise
chooses a site. It commences by boring in the earth with the end of
its tail, the muscles of which are held firmly contracted; it turns
the tail like a gimlet and succeeds in making a conical hole.
Gradually the depth of the hole becomes equal to the length of the
tail, and the tool then becomes useless. The _Cistudo_ enlarges the
cavity with the help of its posterior legs. Using them alternately it
withdraws the earth and kicks it away, then piles up this rubbish on
the edge of the hole, arranging it so as to form a circular rampart.
Soon the posterior members can take nothing more from the too distant
bottom. The moment for laying has now come. As soon as the egg arrives
at the cloaca one of the feet seizes it and lowers it gently into the
nest, while the second foot seizes another egg, which during this time
had appeared at the orifice. This manipulation lasts until the end of
the operation, when the tortoise buries all its family, and to flatten
the prominence which results she strikes it repeatedly with her
plastron, raising herself on her legs.
It is not only land animals which adopt this custom of living in the
earth, and there sheltering their offspring. Fish also make retreats
on the bank or at the bottom. To mention only one case, the Bullhead
(_Cottus gobio_) of our rivers, which spawns in the Seine in May,
June, and July, acts in this manner. Beneath a rock in the sand it
prepares a cavity; then seeks females and brings them to lay eggs in
its little lodging. During the four or five weeks before they come out
it watches the eggs, keeping away as far as possible every danger
which threatens them. It only leaves its position when pressed by
hunger, and as soon as the hunt is concluded, returns to the post of
duty.
Other animals when digging have a double object; they wish to shelter
themselves, and at the same time to find the water which they need for
themselves or for the development of their young.
It is well known that Frogs and Toads generally go in the spring to
lay their eggs in streams and ponds. A Batrachian of Brazil and the
hot regions of South America, the _Cystignathus ocellatus_, no doubt
fearing too many dangers for the spawn if deposited in the open water,
employs the artifice of hollowing, not far from the bank, a hole the
bottom of which is filled by infiltration. It there places its eggs,
and the little ones on their birth can lead an aquatic life while
being guaranteed against its risks.
A terrestrial Crab, the _Cardisoma carnifex_, found in Bengal and the
Antilles, acts in the same manner; but in this case it has in view its
own convenience and not care for its offspring. Its habitat is
especially in low-lying spots near the shore, where water may be found
at a trifling depth beneath the soil. To establish its dwelling, the
Crustacean first buries itself until it reaches the liquid level.
Arrived at this point, it makes a large lair in the soft soil, and
effects communication with the outside by various openings. It can
thus easily come and go and retire into its cave, where it finds
security and a humidity favourable for branchial respiration. From
time to time it cleans out the dirt and rubbish which accumulate in
the hole. It makes a little pile of all the refuse which it finds,
and, seizing it between its claws and abdomen, carries it outside.
Executing several journeys very rapidly, it soon clears out its
dwelling.
The dipnoid _Protopterus_, which inhabits the marshes of Senegal and
Gambia, is curious in more than one respect. Firstly, it can breathe
oxygen, whether, like other fish, it finds it dissolved in water or in
the atmospheric air. When during the summer the marshes in which it
lives dry up, it takes refuge in the mud at the bottom, which hardens
and imprisons it, and it thus remains curled up until the time when
the water after the rainy season has softened the earth which
surrounds it. This fact had been known for some time; travellers had
brought back lumps of dried earth of varied size, the largest about as
big as two fists. On opening them the same fish was always found
within, and the chamber in which it is contained was lined with a sort
of cocoon, having the appearance of dry gelatine. Dumeril was able to
observe one of these animals in captivity. At the period corresponding
to the dry period of its own country, the _Protopterus_ buried itself
in the mud which had been placed at the bottom of the aquarium. In
order to realise the conditions found in nature, the water which
covered it was gradually withdrawn. The earth hardened in drying, and
when broken the recluse was seen surrounded by hardened mucus, exactly
like those which came from Senegal.
_Carefully-disposed burrows._--All the cases which we have considered
show us the industry of the hollowed dwelling in its primitive state;
but other animals know how to furnish it with greater luxury. I will
continue in the same order of increasing complication. Many beings
live permanently in a burrow; Reptiles--Snakes or Lizards--are to be
placed among these. Among others, the _Lacerta stirpium_ arranges a
narrow and deep hole, well hidden beneath a thicket, and retires into
it for the winter, when cold renders it incapable of movement and at
the mercy of its enemies. Before giving itself up to its hybernal
sleep, it is careful to close hermetically the opening of the dwelling
with a little earth and dried leaves. When spring returns and the heat
awakens the reptile, it comes out to warm itself and to hunt, but
never abandons its dwelling, always retiring into it in case of alarm
and to pass there cold days and nights.
Darwin has observed and described[82] how a little Lacertilian, the
_Conolophus subcristatus_, conducts its work of mining and digging. It
establishes its burrow in a soft tufa, and directs it almost
horizontally, hollowing it out in such a way that the axis of the hole
makes a very small angle with the soil. This reptile does not
foolishly expend its strength in this troublesome labour. It only
works with one side of its body at a time, allowing the other side to
rest. For instance, the right anterior leg sets to work digging, while
the posterior leg on the same side throws out the earth. When
fatigued, the left legs come into play, allowing the others to repose.
[82] _Voyage of the Beagle_.
Other animals, without building their cavern with remarkable skill,
show much sagacity in the choice of a site calculated to obtain
certain determined advantages. In Egypt there are dogs which have
become wild. Having shaken off the yoke of man, which in the East
affords them little or no support, they lead an independent life.
During the day they remain quiescent in desert spots or ruins, and at
night they prowl about like jackals, hunting living prey or feeding on
abandoned carcasses. There are hills which have in a manner become the
property of these animals. They have founded villages there, and allow
no one to approach. These hills have an orientation from north to
south, so that one slope is exposed to the sun from morning to mid-day
and the other from mid-day to evening. Now, dogs have a great horror
of heat. They fear the torrid heat of the south as much as in our
climate they like to lie warmed by gentle rays; there is no shadow too
deep for their siesta. Therefore, on these Egyptian hills every dog
hollows out a lair on both slopes. One of these dwellings is thus
turned towards the east, the other towards the west. In the morning,
when he returns from his nocturnal expeditions, the animal takes
refuge in the second, and remains there until mid-day, sunk in
refreshing sleep. At that hour the sun begins to reach him, and to
escape it he passes over to the opposite slope; it is a curious sight
to see them all, with pendent heads and sleepy air, advance with
trailing steps to their eastern retreat, settle down in it, and
continue their dream and their digestion till evening, when they again
set forth to prowl. We never grow tired of admiring the intelligence
of their domesticated fellows, but this trait seems to me worthy of
remark; it proves a very developed power of observation and
reflection.
[Illustration: FIG. 20.]
[Illustration: FIG. 21.]
The Trap-door Spiders of the south of Europe construct burrows which
have been studied with great care and in much detail by Moggridge.[83]
He found that there were four chief types of burrow, shown in the
accompanying illustration (Fig. 20) at about one-third the actual size
(except C1 and D1, which are of natural size). While A and B have only
one door, C and D, besides the surface door, have another a short way
under ground. The whole burrow as well as the door are lined with
silk, which also forms the hinge. The great art of the Trap-door
Spider lies in her skilful forming of the door, which fits tightly,
although it opens widely when she emerges, and which she frequently
holds down when an intruder strives to enter, and in the manner with
which the presence of the door is concealed, so as to harmonise with
surrounding objects. Perhaps in no case is the concealment more
complete than when dead leaves are employed to cover the door. In some
cases a single withered olive leaf is selected, and it serves to cover
the entrance; in other cases several are woven together with bits of
wood or roots, as in the accompanying illustration, which represents
such a door when open and when shut. (Fig. 21.)
[83] J. T. Moggridge, _Harvesting Ants and Trap-door
Spiders_, contained in two elaborately illustrated volumes,
London, 1873-74.
The Trap-door Spider (_Mygale henzii_, Girard), which is widely
diffused in California, forms a simple shaft-like burrow, but, like
the European Trap-door Spider, it is very skilful in forming an entrance
and in concealing its presence. Its habits have lately been described
by D. Cleveland of San Diego.[84] In the adobe land hillocks are
numerous; they are about a foot in height, and some three or four feet
in diameter. These hillocks are selected by the spiders--apparently
because they afford excellent drainage, and cannot be washed away by
the winter rains--and their stony summits are often full of spiders'
nests. These subterranean dwellings are shafts sunk vertically in the
earth, except where some stony obstruction compels the miner to
deflect from a downward course. The shafts are from five to twelve
inches in depth, and from one-half to one and a half inches in
diameter, depending largely upon the age and size of the spider.
[84] _Science_, 20th January 1893.
When the spider has decided upon a location, which is always in clay,
adobe or stiff soil, he excavates the shaft by means of the sharp
horns at the end of his mandibles, which are his pick and shovel and
mining tools. The earth is held between the mandibles and carried to
the surface. When the shaft is of the required size, the spider
smoothes and glazes the wall with a fluid which is secreted by itself.
Then the whole shaft is covered with a silken paper lining, spun from
the animal's spinnerets.
The door at the top of the shaft is made of several alternate layers
of silk and earth, and is supplied with an elastic and ingenious
hinge, and fits closely in a groove around the rim of the tube. This
door simulates the surface on which it lies, and is distinguishable
from it only by a careful scrutiny. The clever spider even glues earth
and bits of small plants on the upper side of his trap-door, thus
making it closely resemble the surrounding surface.
The spider generally stations itself at the bottom of the tube. When,
by tapping on the door, or by other means, a gentle vibration is
caused, the spider runs to the top of his nest, raises the lid, looks
out and reconnoitres. If a small creature is seen, it is seized and
devoured. If the invader is more formidable, the door is quickly
closed, seized and held down by the spider, so that much force is
required to lever it open. Then, with the intruder looking down upon
him, the spider drops to the bottom of his shaft.
It has been found by many experiments that when the door of his nest
is removed, the spider can renew it five times--never more than that.
Within these limitations, the door torn off in the evening was found
replaced by a new one in the morning. Each successive renewal showed,
however, a greater proportion of earth, and a smaller proportion of
silk, until finally the fifth door had barely enough silk to hold the
earth together. The sixth attempt, if made, was a failure, because the
spinnerets had exhausted their supply of the web fluid. When the poor
persecuted spider finds his domicile thus open and defenceless, he is
compelled to leave it, and wait until his stock of web fluid is
renewed.[85]
[85] The Trap-door Spiders of various parts of the world
have been carefully studied, and the gradual development of
their skill traced through various species, by Eugene
Simon; see, for example, _Actes de la Soc. Lin. de
Bordeaux_, 1888.
Skilful diggers prepare burrows with several entrances; some even
arrange several rooms, each for a special object. The Otter seeks its
food in the water, and actively hunts fish in ponds and rivers. But
when fishing is over, it likes to keep dry and at the same time
sheltered from terrestrial enemies. Its dwelling must also present an
easy opening into the water. In order to fulfil all these conditions,
its house consists first of a large room hollowed in the bank at a
level sufficiently high to be beyond reach of floods. From the bottom
of this keep a passage starts which sinks and opens about fifty
centimetres beneath the surface of the water. It is through here that
the Otter noiselessly glides to find himself in the midst of his
hunting domain without having been seen or been obliged to make a
noisy plunge which would put the game to flight. If this were all, the
hermetically-closed dwelling would soon become uninhabitable, as there
would be no provision for renewing the air, so the Otter proceeds to
form a second passage from the ceiling of the room to the ground, thus
forming a ventilation tube. In order that this may not prove a cause
of danger, it is always made to open up in the midst of brushwood or
in a tuft of rushes and reeds.
Marmots also are not afraid of the work which will assure them a warm
and safe refuge in the regions they inhabit, where the climate is
rough. In summer they ascend the Alps to a height of 2,500 to 3,000
metres and rapidly hollow a burrow like that for winter time, which I
am about to describe, but smaller and less comfortable. They retire
into it during bad weather or to pass the night. When the snow chases
them away and causes them to descend to a lower zone, they think about
constructing a genuine house in which to shut themselves during the
winter and to sleep. Twelve or fifteen of these little animals unite
their efforts to make first a horizontal passage, which may reach the
length of three or four metres. They enlarge the extremity of it into
a vaulted and circular room more than two metres in diameter. They
make there a good pile of very dry hay on which they all install
themselves, after having carefully protected themselves against the
external cold by closing up the passage with stones and calking the
interstices with grass and moss.
In solitary woods or roads the Badger (_Meles_), who does not like
noise, prepares for himself a peaceful retreat, clean and well
ventilated, composed of a vast chamber situated about a metre and a
half beneath the surface. He spares no pains over it, and makes it
communicate with the external world by seven or eight very long
passages, so that the points where they open are about thirty paces
distant from one another. In this way, if an enemy discovers one of
them and introduces himself into the Badger's home, the Badger can
still take flight through one of the other passages. In ordinary times
they serve for the aeration of the central room. The animal attaches
considerable importance to this. He is also very clean in his habits,
and every day may be seen coming out for little walks, having an
object of an opposite nature to the search for food. This praiseworthy
habit is, as we shall see, exploited by the Fox in an unworthy manner.
The Fox has many misdeeds on his conscience, but his conduct towards
the Badger is peculiarly indelicate. The Fox is a skilful digger, and
when he cannot avoid it, he can hollow out a house with several rooms.
The dwelling has numerous openings, both as a measure of prudence and
of hygiene, for this arrangement enables the air to be renewed. He
prepares several chambers side by side; one of which he uses for
observation and to take his siesta in; a second as a sort of larder in
which he piles up what he cannot devour at once; a third, in which the
female brings forth and rears her young. But he does not hesitate to
avoid this labour when possible. If he finds a rabbit warren he tries
first to eat the inhabitants, and then, his mind cleared from this
anxiety, arranges their domicile to his own taste, and comfortably
installs himself in it. In South America, again, the Argentine Fox
frequently takes up permanent residence in a vizcachera, ejecting the
rightful owners; he is so quiet and unassuming in his manners that the
vizcachas become indifferent to his presence, but in spring the female
fox will seize on the young vizcachas to feed her own young, and if
she has eight or nine, the young of the whole village of vizcachas may
be exterminated.
The Badger's dwelling appears to the Fox particularly enviable. In
order to dislodge the proprietor he adopts the following plan. Knowing
that the latter can tolerate no ordure near his home, he chooses as a
place of retirement one of the passages which lead to the chamber of
the peaceful recluse. He insists repeatedly, until at last the Badger,
insulted by this grossness, and suffocated by the odour, decides to
move elsewhere and hollow a fresh palace. The Fox is only waiting for
this, and installs himself without ceremony.
The Vizcacha (_Lagostomus trichodactylus_) is a large Rodent
inhabiting a vast extent of country in the pampas of La Plata,
Patagonia, etc. Unlike most other burrowing species, the Vizcacha
prefers to work on open level spots. On the great grassy plains it is
even able to make its own conditions, like the Beaver, and is in this
respect, and in its highly-developed social instinct, among the two or
three Mammals which approach Man, although only a Rodent, and even in
this order, according to Waterhouse, coming very low down by reason of
its marsupial affinities.
The Vizcacha lives in small communities of from twenty to thirty
members, in a village of deep-chambered burrows, some twelve or
fifteen in number, with large pit-like entrances closely grouped
together, and as the Vizcachera, as this village is called, endures
for an indefinitely long period, the earth which is constantly brought
up forms an irregular mound thirty or forty feet in diameter, and from
fifteen to thirty inches above the level of the road; this mound
serves to protect the dwelling from floods on low ground. A clearing
is made all round the abode and all rubbish thrown on the mound; the
Vizcachas thus have a smooth turf on which to disport themselves, and
are freed from the danger of lurking enemies.
The entire village occupies an area of one hundred to two hundred
square feet of ground. The burrows vary greatly in extent; usually in
a Vizcachera there are several that, at a distance of from four to six
feet from the entrance, open into large circular chambers. From these
chambers other burrows diverge in all directions, some running
horizontally, others obliquely downwards to a maximum depth of six
feet from the surface; some of these galleries communicate with those
of other burrows.
On viewing a Vizcachera closely, the first thing that strikes the
observer is the enormous size of the entrances to the central burrows
in the mound; there are usually several smaller outside burrows. The
entrance to some of the principal burrows is sometimes four to six
feet across the mouth, and sometimes it is deep enough for a tall man
to stand in up to the waist.
It is not easy to tell what induces a Vizcacha to found a new
community, for they increase very slowly, and are very fond of each
other's society. It is invariably one individual alone who founds the
new village. If it were for the sake of better pasture he would remove
to a considerable distance, but he merely goes from forty to sixty
yards off to begin operations. Sooner or later, perhaps after many
months, other individuals join the solitary Vizcacha, and they become
the parents of innumerable generations in the same village: old men,
who have lived all their lives in one district, remember that many of
the Vizcacheras around them existed when they were children.
It is always a male who begins the new village. Although he does not
always adopt the same method, he usually works very straight into the
earth, digging a hole twelve or fourteen inches wide, but not so deep,
at an angle of about 25 deg. with the surface. After he has progressed
inwards for a few feet, the animal is no longer content merely to
scatter the loose earth; he cleans it away in a straight line from the
entrance, and scratches so much on this line, apparently to make the
slope gentler, that he soon forms a trench a foot or more in depth,
and often three or four feet in length. This facilitates the
conveyance of the loose earth as far as possible from the entrance of
the burrow. But after a while the animal is unwilling that earth
should accumulate even at the end of this long passage, and proceeds
to form two additional trenches, making an acute or right angle
converging into the first trench, so that the whole when completed
takes a Y shape. These trenches are continually deepened and
lengthened in this manner, the angular segment of earth between them
being scratched away, until by degrees it gives place to one large
deep irregular mouth. The burrows are made best in the black and red
moulds of the pampas; but even in such soils the entrances may be
varied. In some the central trench is wanting, or so short that there
appear to be but two passages converging directly into the burrow, or
these two trenches may be so curved inwards as to form the segment of
a circle. Usually, however, the varieties are only modifications of
the Y-shaped system.
On the pampas a wide-mouthed burrow possesses a distinct advantage
over the more usual shape. The two outer trenches diverge so widely
from the mouth that half the earth brought out is cast behind instead
of before it, thus creating a mound of equal height about the
entrance, by which it is secured from water during great rainfalls,
while cattle avoid treading over the great pit-like entrances, though
they soon tread and break in the burrows of the Armadillo and other
species when these make their homes on perfectly level ground.
The Vizcachas do not usually leave their burrows until dark, but in
summer they come out before sunset. Usually one of the old males first
appears, and sits on some prominent place on the mound, apparently in
no haste to begin his evening meal. Other Vizcachas soon begin to
appear, each quietly taking up his position at the burrow's mouth. The
females, known by their smaller size and lighter colour, sit upright
on their haunches, as if to command a better view; they are always
wilder and sprightlier in their gestures than the males. They view a
human stranger with a mixture of fear and curiosity, sometimes
allowing him to come within five or six paces of them; in desert
regions, however, where enemies are numerous, the Vizcacha is very
timid and wary.
These animals are very sociable, and their sociability extends beyond
their own vizcachera. On approaching a vizcachera at night, usually
some of the Vizcachas on it scamper off to distant burrows. These are
neighbours merely come to pay a friendly visit. The intercourse is so
frequent that little straight paths are formed from one village to
another. Their social instinct leads members of one village to assist
those of another when in trouble. Thus, if a vizcachera is covered
over with earth in order to destroy the animals within, Vizcachas from
distant burrows will subsequently be found zealously digging out their
friends. The hospitality of the Vizcacha does not, however, extend to
his burrow; he has a very strong feeling with regard to the sanctity
of the burrow. A Vizcacha never enters another's burrow, and if by
chance driven into one by dogs will emerge speedily, apparently
finding that the danger within is greater than the danger without. In
connection with the sociability of the Vizcacha, we must take into
consideration the fact that Vizcachas possess a wonderfully varied and
expressive language, and are engaged in perpetual discussion all night
long.[86]
[86] The Vizcacha has been carefully studied by Mr. W. H.
Hudson, whose account has here been closely followed,
_Proceedings of the Zoological Society_, 1872, and
_Naturalist in La Plata_, 1892, pp. 289-313.
_Burrows with barns adjoined._--Certain Rodents have carried hollow
dwellings to great perfection. Among these the Hamster of Germany
(_Cricetus frumentarius_) is not the least ingenious. To his
dwelling-room he adds three or four storehouses for the amassed
provisions of which I have already had occasion to speak. The burrow
possesses two openings: one, which the animal prefers to use, which
sinks vertically into the soil; the other, the passage of exit with a
gentle and very winding slope. The bottom of the central room is
carpeted with moss and straw, which make it a warm and pleasant home.
A third tunnel starts from this sleeping chamber, soon forking and
leading to the wheat barns. Thus during the winter the Hamster has no
pressing need to go out except on fine days for a little fresh air. He
has everything within his reach, and can remain shut up with nothing
to fear from the severity of the season.
_Dwellings hollowed out in wood._--It is not only the soil which may
serve for retreat; wood serves as an asylum for numerous animals, who
bore it, and find in it both food and shelter. In this class must be
placed a large number of Worms, Insects, and Crustaceans. One of these
last, the _Chelura terebrans_, a little Amphipod, constitutes a great
danger for the works of man. It attacks piles sunken to support
structures, and undermines them to such a degree that they eventually
fall. Wood is formed of concentric layers alternately composed of
large vessels formed during the summer, and smaller vessels formed
during the winter. The latter zones are more resistant, the former are
softer. When one of these Crustaceans attacks a pile, it first bores a
little horizontal passage, stopping at a layer of summer-growth. It
there hollows a large grotto, leaving here and there pillars of
support. It lays in this space. The new generation working around the
parents increases the space and feeds on the wood removed. A second
generation is produced, and the inhabitants become pressed for space.
The new-born pierce numerous passages and penetrate towards the
interior of the pile as far as the next summer layer. There they
spread themselves, always boring; they construct new rooms like the
first, and arrange pillars here and there. Their descendants gain the
subjacent zone, and so the process goes on. During this time the early
ancestors who hollowed the surface dwellings have died, and the holes
which they made are no longer habitable; but they have all contributed
to diminish the resistance of the wood, and this continues as long as
the race which they produced makes its way towards the centre of the
stake.
[Illustration: FIG. 22.]
An insect, the _Xylocopa violacea_ (Fig. 22), related to our
Humble-bee, from which it differs in several anatomical characters,
and by the dark violet tint of its wings, brings an improvement to the
formation of the shelter which it makes in wood for its larvae. Instead
of hollowing a mere retreat to place there all its eggs
indiscriminately, it divides them into compartments, separated by
horizontal partitions. It is the female alone who accomplishes this
task, connected with the function of perpetuating the race. She
chooses an old tree-trunk, a pole, or the post of a fence, exposed to
the sun and already worm-eaten, so that her labour may be lightened.
She first attacks the wood perpendicularly to the surface, then
suddenly turns and directs downwards the passage, the diameter of
which is about equal to the size of the insect's body. The _Xylocopa_
thus forms a tube about thirty centimetres in length. Quite at the
bottom she places the first egg, leaving beside it a provision of
honey necessary to nourish the larva during its evolution; she then
closes it with a partition. This partition is made with fragments of
the powder of wood glued together with saliva. A first horizontal ring
is applied round the circumference of the tube; then in the interior
of this first ring a second is formed, and so on continuously, until
the central opening, more and more reduced, is at last entirely closed
up. This ceiling forms the floor for the next chamber, in which the
female deposits a new egg, provided, like the other, with abundant
provisions. The same acts are repeated until the retreat becomes
transformed into a series of isolated cells in which the larvae can
effect their development, and from which they will emerge either by
themselves perforating a thin wall which separates them from daylight,
or by an opening which the careful mother has left to allow them to
attain liberty without trouble.[87]
[87] Reaumur, _Memoires pour servir a l'histoire des
Insectes_, pp. 97 _et seq._
_Woven dwellings._--The second class of habitation, which I have
called the woven dwelling, proceeds at first from the parcelling up of
substances, then of objects capable of being entangled like wisps of
wood or straw, then of fine and supple materials which the artisan can
work together in a regular manner, that is to say by felting or
weaving. Facts will show us the successive stages of improvement which
have been introduced into this industry. I will begin with the more
rudimentary.
_Rudiments of this industry._--There are, first, cases in which the
will of the animal does not intervene, or at least is very slightly
manifested. The creature is found covered and protected by foreign
bodies which are often living beings. Spider-crabs (_Maia_), for
example, have their carapaces covered with algae and hydroids of all
sorts. Thus garnished, the Crustaceans have the advantage of not being
recognised from afar when they go hunting, since beneath this fleece
they resemble some rock. H. Fol has observed at Villefranche-sur-Mer a
_Maia_ so buried beneath this vegetation that it was impossible at
first sight to distinguish it from the stones around. Under these
conditions the animal submits to a shelter rather than creates it. Yet
it is not so passive as one might at first be led to suppose. When the
algae which flourish on its back become too long and impede or delay
its progress, it tears them off with its claws and thoroughly cleans
itself. The carapace being quite clean, the animal finds itself too
smooth and too easy to distinguish from surrounding objects; it
therefore takes up again fragments of algae and replaces them where
they do not delay to take root like cuttings and to flourish anew.
This culture is therefore intentional; the crab directs it and arrests
its exuberance; it is no more the victim of it than the gardener is
the slave of the vegetables which he waters day by day. From
generation to generation this crab has acquired the habit, the
instinct if one prefers, of thus covering itself so that it may be
confused with neighbouring objects. Naturally it is ignorant of
botany, and knows nothing of cuttings. If placed in an aquarium with
little fragments of paper it will seize them and place them on its
back, as it would have done with algae, without troubling as to whether
they become fixed or not. In spite of this lack of judgment, we cannot
fail to recognise in this _Maia_ a certain ingenuity in
self-concealment.
[Illustration: FIG. 23.]
The Sponge-crab (_Dromia vulgaris_) also practises this method of
shelter. It seizes a large sponge and maintains it firmly over its
carapace with the help of the posterior pair of limbs. The sponge
continues to prosper and to spread over the Crustacean who has adopted
it. (Fig. 23.) The two beings do not seem to be definitely fixed to
each other; the contact of a sudden wave will separate them. When the
divorce is effected, the _Dromia_ immediately throws itself on its
cherished covering and replaces it. M. Kuenckel d'Herculais tells of
one of these curious crustaceans which delighted the workers in the
laboratory of Concarneau. The need for covering themselves experienced
by these Crabs is so strong that in aquariums when their sponge is
taken away they will apply to the back a fragment of wrack or of
anything which comes to hand. A little white cloak with the arms of
Brittany was manufactured for one of these captives, and it was very
amusing to see him put on his overcoat when he had nothing else
wherewith to cover himself.[88]
[88] Brehm, edition Francaise, _Crustaces_, p. 738.
In these two cases which I have brought forward to exhibit the
rudiments of this industry, the animals' reflection and will play but
a small part; even in the _Dromia_ custom is so inveterate in the race
that it has reacted on the animal's organisation, and its four
posterior legs are profoundly modified for the purpose of firmly
holding the sheltering sponge; they no longer serve for swimming or
walking. The animals of which I have now to speak possess more
initiative; although all do not act with the same success, or show
themselves equally skilful. Let us turn first to the least
experienced.
An Australian bird, the _Catheturus Lathami_, as described by Gould,
is still in the rudiments, and limits itself to preparing an enormous
pile of leaves. It begins its work some weeks before laying its eggs;
with its claws it pushes behind it all the dead leaves which fall on
the earth and brings them into a heap. The bird throws new material on
the summit until the hole is of suitable height. This detritus
ferments when left to itself, and a gentle heat is developed in the
centre of the edifice. The _Catheturus_ returns to lay near this
coarse shelter; it then takes each egg and buries it in the heap, the
larger end uppermost. It places a new layer above, and quits its
labour for good. Incubation takes place favoured by the uniform heat
of this decomposing mass, hatching is produced, and the young emerge
from their primitive nest.
[Illustration: FIG. 24.]
Birds are not alone in constructing temporary dwellings in which to
lay their eggs; some Fish are equally artistic in this kind of
industry, and even certain Reptiles. The Alligator of the Mississippi
would not perhaps at first be regarded as a model of maternal
foresight. Yet the female constructs a genuine nest. She seeks a very
inaccessible spot in the midst of brushwood and thickets of reeds.
With her jaw she carries thither boughs which she arranges on the soil
and covers with leaves. She lays her eggs and conceals them with care
beneath vegetable remains. Not yet considering her work completed, she
stays in the neighbourhood watching with jealous eye the thicket which
shelters the dear deposit, and never ceases to mount guard
threateningly until the day when her young ones can follow her into
the stream.
A hymenopterous relative of the Bees, the _Megachile_, cuts out in
rose-leaves fragments of appropriate form which it bears away to a
small hole in a tree, an abandoned mouse nest or some similar cavity.
There it rolls them, works them up, and arranges them with much art,
so as to manufacture what resemble thimbles, which it fills with honey
and in which it lays.[89] (Fig. 24.)
[89] Reaumur, _Memoires pour servir a l'histoire des
Insectes_, pp. 97 _et seq._
The _Anthocopa_ acts in a similar manner, carpeting the holes of which
it takes possession with the delicate petals of the corn poppy.
The retreats of nocturnal birds of prey do not differ in method of
construction from these two kinds of nests. They are holes in trees,
in ruins, in old walls, and are lined with soft and warm material.
These dwellings are related, not to the type of the hollowed cave, but
to that of the habitation manufactured from mingled materials. They
constitute an inferior form in which the pieces are not firmly bound
together but need support throughout. The cavity is the support which
sustains the real house.
_Dwellings formed of coarsely-entangled materials._--Diurnal birds of
prey are the first animals who practise skilfully the twining of
materials. Their nests, which have received the name of eyries, are
not yet masterpieces of architecture, and reveal the beginning of the
industry which is pushed so far by other birds. Usually situated in
wild and inaccessible spots, the young are there in safety when their
parents are away on distant expeditions. The abrupt summits of cliffs
and the tops of the highest forest trees are the favourite spots
chosen by the great birds of prey. The eyrie generally consists of a
mass of dry branches which cross and mutually support one another,
constituting a whole which is fairly resistant.
Even these primitive nests are not, however, without more complicated
details of interest. Thus Mr. Denis Gale wrote to Bendire concerning
the Golden Eagle in America: "Here in Colorado, in the numerous glades
running from the valleys into the foothills, high inaccessible ledges
are quite frequently met with which afford the Eagles secure sites for
their enormous nests. I know of one nest that must contain two
waggon-loads of material. It is over seven feet high, and quite six
feet wide on its upper surface. In most cases the cliff above
overhangs the site. At the end of February or the beginning of March,
the needful repairs to the nest are attended to, and the universal
branch of evergreen is laid upon the nest, seemingly for any purpose
save that of utility. This feature has been present in all the nests I
have examined myself, or have had examined by others; it would seem to
be employed as a badge of occupancy."[90] This curious feature is also
found in the nests of the Bald or American Eagle. Thus Dr. W. L. Ralph
furnished Bendire with the following observations made in Florida on
the dwellings of this, the national bird of the United States:--"The
nests are immense structures, from five to six feet in diameter, and
about the same in depth, and so strong that a man can walk around in
one without danger of breaking through; in fact, my assistant would
always get in the nest before letting the eggs down to me. They are
composed of sticks, some of which are two or three inches thick, and
are lined with marsh grass or some similar material. There is usually
a slight depression in the centre, where the eggs are placed, but the
edge of the nest extends so far beyond this that it is almost
impossible to see the bird from below, unless it has its head well up.
I have frequently found foreign substances in their nests, usually
placed on the edges of it, the object of which I cannot account for.
Often it would be a ball of grass, wet or dry, sometimes a green
branch from a pine tree, and again a piece of wood, bark, or other
material. It seemed as if they were placed in the nests as if to mark
them. From its frequent occurrence, at least, it seemed to me as if
designedly done."[91]
[90] _Life Histories of North American Birds_, 1892, p. 265.
[91] _Life Histories of American Birds_, p. 275.
The abodes of Squirrels, though exhibiting more art, are constructions
of the same nature; that is to say, they are formed of interlaced
sticks. This animal builds its home to shelter itself there in the bad
season, to pass the night in it, and to rear its young. Very agile,
and not afraid of climbing, it places its domicile near the tops of
our highest forest trees. Rather capricious also, and desiring change
of residence from time to time, it builds several of them; at least
three or four, sometimes more. The materials which it needs are
collected on the earth among fallen dead branches, or are torn away
from the old abandoned nest of a crow or some other bird. The Squirrel
firsts builds a rather hollow floor by intermingling the fragments of
wood which it has brought. In this state its dwelling resembles a
magpie's nest. But the fastidious little animal wishes to be better
protected and not thus to sleep in the open air. Over this foundation
he raises a conical roof; the sticks which form it are very skilfully
disposed, and so well interlaced that the whole is impenetrable to
rain. The house must still be furnished, and this is done with
oriental luxury; that is to say, the entire furniture consists of a
carpet, a carpet of very dry moss, which the Squirrel tears from the
trunks of trees, and which it piles up so as to have a soft and warm
couch. An entrance situated at the lower part gives access to the
aerial castle; it is usually directed towards the east. On the
opposite side there is another orifice by which the animal can escape
if an enemy should invade the principal entrance. In ordinary times
also it serves to ventilate the chamber by setting up a slight current
of air. The Squirrel greatly fears storms and rain, and during bad
weather hastens to take refuge in his dwelling. If the wind blows in
the direction of the openings, the little beast at once closes them
with two stoppers of moss, and keeps well shut in as long as the storm
rages.
The great Anthropoid Apes have found nothing better for shelter than
the Squirrels' method. It must, however, be taken into account that
they have much more difficulty in arranging and maintaining much
heavier rooms, and in building up a shelter with larger surface.
The Orang-outang, which lives in the virgin forests of the Sunda
Archipelago, does not feel the need of constructing a roof against the
rain. He is content with a floor established in the midst of a tree,
and made of broken and interlaced branches. He piles up on this
support a considerable mass of leaves and moss; for the Orang does not
sleep seated like the other great apes, but lies down in the manner of
Man, as has often been observed when he is in captivity. When he feels
the cold he is ingenious enough to cover himself with the leaves of
his couch.
In Upper and Lower Guinea the Chimpanzee (_Troglodytes niger_) also
establishes his dwelling on trees. He first makes choice of a large
horizontal branch, which constitutes a sufficient floor for the agile
animal. Above this branch he bends the neighbouring boughs, crosses
them, and interlaces them so as to obtain a sort of framework. When
this preliminary labour is accomplished, he collects dead wood or
breaks up branches and adds them to the first. Before commencing he
had taken care when choosing the site that the whole was so arranged
that a fork was within reach to sustain the roof. He thus constructs a
very sufficient shelter. These apes are sociable and prefer to live in
each other's neighbourhood. They even go on excursions in rather large
bands. Notwithstanding this, more than one or two cabins are never
seen on the same tree; perhaps this is because the complicated
conditions required for the construction are not likely to be realised
several times on the same tree; perhaps also it is a desire for
independence which impels the Chimpanzees not to live too near to each
other.[92]
[92] Savage, "Observations on the External Characters and
Habits of the _Troglodytes niger_," _Boston Journal Nat.
Hist._, 1843, pp. 362-376.
The _Troglodytes calvus_, a relative of the preceding, inhabiting the
same regions, as described by Du Chaillu, shows still more skill in
raising his roof. A tree is always chosen for support. He breaks off
boughs and fastens them by one end to the trunk, by the other to a
large branch. To fix all these pieces he employs very strong creepers,
which grow in abundance in his forests. Above this framework, which
indicates remarkable ingenuity, the animal piles up large leaves,
forming in layers well pressed down and quite impenetrable to the
rain. The whole has the appearance of an open parasol. The ape sits on
a branch beneath his handiwork, supporting himself against the trunk
with one arm. He has thus an excellent shelter against the mid-day sun
as well as against tropical showers. Male and female each possess a
dwelling on two neighbouring trees, the principle of conjugal
cohabitation not being admitted in this species. As to the child, it
appears that it sleeps near its mother, until it is of age to lead an
independent life.
There exists in Australia, the country of zoological singularities, a
bird with very curious customs. This is the Satin Bower-bird. The art
displayed in this bird's constructions is not less interesting than
the sociability he gives evidence of, and his desire to have for his
hours of leisure a shelter adorned to his taste. The bowers which he
constructs, and which present on a small scale the appearance of the
arbours in our old gardens, are places for re-union and for warbling
and courtship, in which the birds stay during the day, when no anxiety
leads them to disperse. They are not, properly speaking, nests built
for the purpose of rearing young; for at the epoch of love each couple
separates and constructs a special retreat in the neighbourhood of the
bower. These shelters are always situated in the most retired parts of
the forest, and are placed on the earth at the foot of trees. Several
couples work together to raise the edifice, the males performing the
chief part of the work. At first they establish a slightly convex
floor, made with interlaced sticks, intended to keep the place
sheltered from the moisture of the soil. The arbour rises in the
centre of this first platform. Boughs vertically arranged are
interlaced at the base with those of the floor. The birds arrange them
in two rows facing each other; they then curve together the upper
extremities of these sticks, and fix them so as to obtain a vault. All
the prominences in the materials employed are turned towards the
outside, so that the interior of the room may be smooth and the birds
may not catch their plumage in it. This done, the little architects,
to embellish their retreat, transport to it a number of conspicuous
objects, such as very white stones from a neighbouring stream, shells,
the bright feathers of the parroquet, whatever comes to their beak.
All these treasures are arranged on the earth, before the two entries
to the bower, so as to form on each side a carpet, which is not
smooth, but the varied colours of which rejoice the eye. The prettiest
treasures are fixed into the wall of the hut. These houses of
pleasure, with all their adornments, form a dwelling very much to the
taste of this winged folk, and the birds pass there the greater part
of the day, preening their feathers and narrating the news of the
forest. Bower-birds' clubs are drawing-rooms raised at the common
expense by all who frequent them. The Spotted Bower-bird, the
_Chlamydera maculata_, which also lives in the interior of Australia,
exercises this method of construction with equal success. The bowers
built by these birds may be one metre in length; this is on a very
luxurious scale, the animal itself only measuring twenty-five
centimetres. In this species, as among other Bower-birds, the bowers
are not the labour and the property of a single couple; they are the
result of the collaboration of several households, who come together
to shelter themselves there. These birds feed only on grains, so that
it is to a very pronounced taste for collecting that we must attribute
this mania of piling up before the entrance of the bower white stones,
shells, and small bones. (Fig. 25.) These objects are intended solely
for the delight of these feathered artists. They are very careful also
only to collect pieces which have been whitened and dried by the
sun.[93]