when pressed by hunger in the bad season, is well known. In time
of war they follow armies, to attack stragglers and to devour the
dead. In Siberia they pursue sledges on the snow with terrible
perseverance, and the pack is not delayed by the massacre of those
who are shot. A few stop to devour at once their fallen comrades,
while the others continue the pursuit.
Besides these brutal chases wolves seem able to exercise a genuine
feint. Sometimes it is a couple who hunt in concert. If they meet
a flock, as they are well aware that the dog will bravely defend
the animals intrusted to him, that he is vigilant, and that his
keen scent will bring him on them much sooner than the shepherd,
it is with him that they first occupy themselves. The two wolves
approach secretly; then suddenly one of them unmasks and attracts
the attention of the dog, who rushes after him with such ardor
that he fails to perceive that in the meantime the second thief
has seized the sheep and dragged it into the wood. The dog finally
renounces his pursuit of the fugitive and returns to his flock. Then
the two confederates join each other and share the prey. In other
circumstances it is a wolf who hunts with his female. When they wish
to obtain possession of a deer, whose robust flight may last a long
time, one of the couple, the male, for example, pursues him and
directs his chase in such a way that the game must pass by a place
where the female wolf is concealed. She then takes up the chase while
the male reposes. It is an organized system of relays. The strength
of the deer becomes necessarily exhausted; he can not resist the
animation shown by his active foe, and is seized and killed. Then the
other wolf calmly approaches the place of the feast to share his part
of the booty.
The fox also successfully uses this method of coursing with relays.
It has often been repeated that man is the only creature sufficiently
intelligent to utilize as weapons exterior objects like a stone or
a brick; in a much greater degree, therefore, it was said, was he
the only creature capable of striking from afar with a projectile.
Nevertheless creatures so inferior as fish exhibit extreme skill in
the art of reaching their prey at a distance. Several act in this
way. There is first the Toxotes jaculator, who lives in the rivers of
India. His principal food is formed by the insects who wander over
the leaves of aquatic plants. To wait until they fell into the water
would naturally result in but meagre fare. To leap at them with one
bound is difficult, not to mention that the noise would cause them to
flee. The Toxotes knows a better trick than that. He draws in some
drops of water, and, contracting his mouth, projects them with so
much force and certainty that they rarely fail to reach the chosen
aim, and to bring into the water all the insects he desires. Other
animals also squirt various liquids, sometimes in attack, but more
especially in defence. The Cephalopods, for example, emit their ink,
which darkens the water and allows them to flee. Certain insects
exude bitter or fœtid liquids; but in all these cases, and in others
that are similar, the animal finds in his own organism a secretion
which happens to be more or less useful to his conservation. The
method of the Toxotes is different. It is a foreign body which he
takes up, and it is an intended victim at which he takes aim and
which he strikes; his movements are admirably co-ordinated to obtain
a precise effect.
Another fish, the Chelinous of Java, also acts in this manner. He
generally lives in estuaries. It is, therefore, a brackish water
which he takes up and projects by closing his gills and contracting
his mouth; he can thus strike a fly at a distance of several feet.
Usually he aims sufficiently well to strike it at the first blow,
but sometimes he fails. Then he begins again until he has succeeded,
which shows that his movements are not those of a machine. He knows
what he is doing, what effect ought to be produced, and whether this
desired result has happened, and he perseveres until the insect has
fallen. These facts are unquestioned; the Chinese preserve these
curious fish in jars, and amuse themselves by making them carry on
this little exercise. Many observers have witnessed and described it.
THE DEATH-FEIGNING INSTINCT
--W. H. HUDSON
Most people are familiar with the phenomenon of “death-feigning,”
commonly seen in coleopterous insects and in many spiders. This
highly curious instinct is also possessed by some vertebrates.
In insects, it is probably due to temporary paralysis occasioned
by sudden concussion, for when beetles alight abruptly, though
voluntarily, they assume that appearance of death which lasts for a
few moments. Some species, indeed, are so highly sensitive that the
slightest touch, or even a sudden menace, will instantly throw them
into this motionless, death-simulating condition. Curiously enough,
the same causes which produce this trance in slow-moving species,
like those of Scarabæus, for example, have a precisely contrary
effect on species endowed with great activity. Rapacious beetles,
when disturbed, scuttle quickly out of sight, and some water-beetles
spin about the surface, in circles or zigzag lines, so rapidly as
to confuse the eye. The common long-legged spiders (Pholcus) when
approached draw their feet together in the middle of the web, and
spin the body round with such velocity as to resemble a whirligig.
Certain mammals and birds also possess the death-simulating instinct,
though it is hardly possible to believe that the action springs
from the same immediate cause in vertebrates and in insects. In the
latter, it appears to be a purely physical instinct, the direct
result of an extraneous cause, and resembling the motions of a plant.
In mammals and birds, it is evident that violent emotion, and not the
rough handling experienced, is the final cause of the swoon.
Passing over venomous snakes, skunks, and a few other species in
which the presence of danger excites only anger, fear has a powerful,
and in some cases a disabling, effect on animals; and it is this
paralyzing effect of fear on which the death-feigning instinct, found
only in a few widely separated species, has probably been built up
by the slow cumulative process of natural selection.
I have met with some curious instances of the paralyzing effect of
fear. I was told by some hunters in an outlying district of the
pampas of its effect on a jaguar they startled, and which took
refuge in a dense clump of dry reeds. Though they could see it, it
was impossible to throw the lasso over its head, and after vainly
trying to dislodge it, they at length set fire to the reeds. Still it
refused to stir, but lay with head erect, fiercely glaring at them
through the flames. Finally, it disappeared from sight in the black
smoke; and when the fire had burned itself out, it was found, dead
and charred, in the same spot.
On the pampas, the Gauchos frequently take the black-necked swan by
frightening it. When the birds are feeding or resting on the grass,
two or three men or boys on horseback go quietly to leeward of the
flock, and, when opposite to it, suddenly wheel and charge it at full
speed, uttering loud shouts, by which the birds are thrown into such
terror that they are incapable of flying, and are quickly despatched.
I have also seen Gaucho boys catch the silver-bill (Lichenops
perspicillata) by hurling a stick or stone at the bird, then rushing
at it, when it sits perfectly still, disabled by fear, and allows
itself to be taken. I myself once succeeded in taking a small bird of
another species in the same way.
Among mammals, our common fox (Canis azaræ), and one of the opossums
(Didelphys azaræ), are strangely subject to the death-simulating
swoon. For it does indeed seem strange that animals so powerful,
fierce and able to inflict such terrible injury with their teeth
should also possess this safeguard, apparently more suited to weak
inactive creatures that can not resist or escape from an enemy and
to animals very low down in the scale of being. When a fox is caught
in a trap or run down by dogs, he fights savagely at first, but by
and by relaxes his efforts, drops on the ground and apparently yields
up the ghost. The deception is so well carried out that dogs are
constantly taken in by it, and no one, not well acquainted with this
clever trickery of nature, but would at once pronounce the creature
dead, and worthy of some praise for having perished in so brave a
spirit.
Now, when in this condition of feigning death, I am sure that the
animal does not altogether lose consciousness. It is exceedingly
difficult to discover any evidence of life in the opossum; but when
one withdraws a little way from the feigning fox, and watches him
very attentively, a slight opening of the eye may be detected; and
finally, when left to himself, he does not recover and start up like
an animal that has been stunned, but slowly and cautiously raises his
head first, and only gets up when his foes are at a safe distance.
Yet I have seen Gauchos, who are very cruel to animals, practice the
most barbarous experiments on a captive fox without being able to
rouse it into exhibiting any sign of life. This has greatly puzzled
me, since if death-feigning is simply a cunning habit, the animal
could not suffer itself to be mutilated without wincing. I can only
believe that the fox, though not insensible, as its behavior on
being left to itself seems to prove, yet has its body thrown by
extreme terror into that benumbed condition which simulates death,
and during which it is unable to feel the tortures practiced upon it.
The swoon sometimes actually takes place before the animal has been
touched, and even when the exciting cause is at a considerable
distance. I was once riding with a Gaucho, when we saw, on the open
level ground before us, a fox, not yet fully grown, standing still
and watching our approach. All at once it dropped, and when we came
up to the spot it was lying stretched out, with eyes closed, and
apparently dead. Before passing on, my companion, who said it was not
the first time he had seen such a thing, lashed it vigorously with
his whip for some moments, but without producing the slightest effect.
The death-feigning instinct is possessed in a very marked degree
by the spotted tinamou or common partridge of the pampas (Nothura
maculosa). When captured, after a few violent struggles to escape, it
drops its head, gasps two or three times, and, to all appearances,
dies. If, when you have seen this, you release your hold, the eyes
open instantly, and, with startling suddenness and a noise of wings,
it is up and away and beyond your reach forever. Possibly, while your
grasp is on the bird, it does actually become insensible, though
its recovery from that condition is almost instantaneous. Birds
when captured do sometimes die in the hand, purely from terror.
The tinamou is excessively timid, and sometimes when birds of this
species are chased--for Gaucho boys frequently run them down on
horseback--and when they find no burrows or thickets to escape into,
they actually drop dead on the plain. Probably, when they feign death
in their captor’s hand, they are in reality very near to death.
BIRDS
--J. ARTHUR THOMSON
Birds are in some ways the highest of the vertebrate animals. They
represent the climax of that passage from water to land which the
backboned series illustrates. Their skeleton is more modified from
the general type than that of mammals; their arrangements for
locomotion, breathing, and nutrition are certainly not less perfect;
their body temperature, higher than that of any other animals, is an
index to the intense activity of their general life; their habitual
and adaptive intelligence is familiarly great, while in range of
emotion and sense impressions they must be allowed the palm. It
is, in fact, only when we emphasize the development of the nervous
system, and the closeness of connection between mother and offspring,
that the mammals are seen to have a right to their pre-eminence over
birds. Birds and mammals represent two divergent lines of progress,
and stand in no close connection, but the affinities between birds
and reptiles are sufficiently marked to warrant their being included
in a common class (Sauropsida), in contrast to the amphibians and
fishes (Ichthyopsida) on the one hand, and Mammalia on the other.
Among the numerous points of difference which separate birds from
their nearest relations, the reptiles, and from mammals, the
following may be noticed:
------------------------+-----------------------+------------------+
| REPTILES | BIRDS |
Covering | Scales or scutes | Feathers |
Number of fingers | Always more than three| At most three |
” ” skull condyles| One | One |
Number of aortic arches | At least two | One, right |
Diaphragm | Only incipient | Only incipient |
Blood | Cold | Hottest |
Position of optic lobes | On top of brain | At sides of brain|
Parturition | Ovi- or viviparous | Oviparous |
------------------------+-----------------------+------------------+
------------------------+----------------------
| MAMMALS
Covering | Hair
Number of fingers | Five or fewer
” ” skull condyles| Two
Number of aortic arches | One, left
Diaphragm | Complete
Blood | Warm
Position of optic lobes | Covered up
Parturition | Except two viviparous
------------------------+----------------------
But those contrasts are only a few of the less technical selected
from Professor Huxley’s masterly comparison of the three classes.
To appreciate the full extent of the resemblances and differences
between birds and reptiles, and the contrast between both and
mammals, the reader must consult Huxley’s _Anatomy of Vertebrate
Animals_.
Most birds use their wings in flight, the feather-covered arms being
raised and depressed with great rapidity by means of the breast
muscles. Every one who has watched birds is familiar with the marked
differences in rapidity and mode of flight. It has been calculated
that a common average of rapidity is about 40 to 60 feet per second,
but records of the feats of carrier-pigeons, etc., certainly greatly
surpass this. It seems probable that strong-winged birds, like
eagles, can cover about 80 feet in a second. Buffon noted that they
disappeared from sight in about three minutes. Strong birds, like
the albatross and birds of prey, can not fly very rapidly, but can
sustain their exertions for long periods, while many other birds
rarely take prolonged flights, except during migration. The ostrich
uses its wings to help it along in its rapid race; some aquatic
birds, like the steamer-duck, use them as paddles, auxiliary to
their legs. On the ground, birds vary greatly in rate and manner of
progression: the swift strides of the ostrich, the rapid run of the
partridge, the hopping of the sparrow are well-known illustrations of
different gaits. That many birds are expert divers and climbers is
also a familiar fact.
The great activity of birds is associated with very efficient
respiration. Expiration, or the expulsion of used air, is managed by
the contraction of breast and abdominal muscles, which compress the
inclosed cavities and force the air from the sacs and lungs. When
these muscles are relaxed the cavities again elastically expand, and
fresh air rushes in by the windpipe to lungs and air sacs.
With few exceptions, birds have a vocal organ, and are able to
produce more or less variable sounds. The organ is, however, wanting
in the running birds, such as the ostrich and the American vultures.
The sounds produced are almost as varied as the different kinds
of birds, and an expert ornithologist has little difficulty in
identifying a great number of forms by their distinctive noises. That
some chirp and others scream, that chattering describes the language
of many and croaking that of others, that some boom and others
bark, that the crows caw, and the laughing jackass laughs, that the
mocking-bird imitates, and the parrot becomes able to articulate, and
above all that the lark trills and the nightingale truly sings, are
well-known illustrations of the variety of bird language. The weird
cry of the curlew or whaup, the melancholy voice of the sea-mew,
the gabble of ducks, the crowing of the cock, the soft cooing of the
dove, the hoarse voice of the corncrake, the ecstatic melody of the
bobolink, the cheerful notes of the blackbird, the educated music of
the canary, are again a random selection of instances from an almost
infinite medley. It is among the so-called perchers, songsters, or
Insessores that we find song really developed, and that for most part
in the males, and in highest degree at breeding time. Though the
notes are not musically pure, many songs of birds have been expressed
in musical notation, and every one is familiar with imitations in
word form. Singing is an unbidden expression of emotional energy. It
is most marked at the high tide of sexual emotion during the breeding
season. It is best, sometimes solely, developed in the males, who use
their powers to attract the females, and often vie with one another
in so doing. In other cases the note is obviously used as language,
expressing alarm and the like, for that some birds are able by voice
to convey impressions to one another is indubitable. In so far as the
song is an instrument and expression of sexual attraction, it fails
to be included among those powers which have been strengthened and
developed by sexual selection.
After the strain of the reproductive period, or sometimes at
the low ebb of mid-winter, the old feathers drop off, and birds
undergo annual moult. The use of this in replacing breakage, and in
furnishing a complete machinery for the flight of migration, is very
evident; the cause is not yet sufficiently investigated. Moulting
obviously presents some analogies with skin-casting and hair-shedding
in other animals, and must be associated with some deep-seated
constitutional change, such as its connection with the end of the
breeding season suggests. Besides this annual growth of new feathers,
many birds exhibit double and some triple moulting. The ptarmigan,
for instance, changes its suit three times in the year, moulting
after breeding into gray, changing this for white as the winter
sets in, and acquiring in spring a third and most attractive set of
feathers. In association with sexual attraction many male birds seem
to undergo a partial moult, as the result of which they acquire those
special decorations which are the index of a reproductive climax.
Birds usually pair in springtime, but to this rule there are many
exceptions. Fertilization is internal, and all birds are oviparous.
The number of eggs is often in inverse proportion to the size of the
bird. Several, such as the apteryx, lay only one; the doves and birds
of prey lay two or three, but the majority of birds many more.
It is important to notice that the higher development of birds,
as compared with reptiles, is associated with the production of
fewer offspring, but at the same time with the enormous increase
of parental care and sacrifice. If the young are to be developed
within the eggs, the latter must be kept at an approximately
constant warmth. In almost all cases this is effected by brooding,
the frequent helplessness of the young, the very common arboreal
habit, the not infrequent enemies, have necessitated a most varied
series of nest-building contrivances. The nest is built before the
eggs are ready to be laid, and in most cases the female takes the
prominent part in its construction. But both in the building and
in the subsequent brooding the male may do his share, or in some
cases much more. Each species usually has its own peculiar style
and material of construction, though this may be adapted to varying
conditions. The nests are usually solitary, more rarely grouped,
and very exceptionally (as among cassowaries and ostriches) common
property. Rooks, sea-fowl, herons, are familiar examples of breeding
communities, while the sociable grosbeak, the republican swallows,
and a few others, form even closer associations. The cuckoo and
the cowbird have managed by a sort of parasitism to shirk their
task, and quite a number of birds lay their eggs in an exceptional
manner in the nests of neighbors. The beak is the organ most used
in construction, but the pressure of the body may round off the
forming nest, and the feet may also be used. How comfortable a nest
may be made inside every one knows; how adroitly hidden it may be
by external decorations of moss and lichen is familiar to every
nest-hunter. The smaller birds usually build the more beautiful
nests, and every variety occurs, from the comparatively careless hole
in the sand made by the ostrich to the skilfully suspended and neatly
fashioned nest of the tailor-bird. It must be noticed that habits
vary considerably, as the very diverse nests built in different
circumstances by falcon, eagle, heron, etc., well illustrate. Nests
are shifted to suit food-supply, and vary in structure according to
the available material. And again, since nest-building is obviously
an acquired habit, which gradually rewarded the species in the
greater success of both parent and offspring during breeding time,
it is natural to find it dispensed with in many cases where the
nature of the situation rendered no actual nest necessary, or where
the birds for some other reason have never learned the habit. Some
sea-birds, like the auk, simply lay on the rocky ledges of their
haunts; some ground-birds simply deposit their eggs on the bare soil.