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Descent of Man [ 1871]

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« Reply #180 on: February 10, 2009, 01:23:14 pm »

Chapter XVIII - Secondary Sexual Characters of Mammals- Continued

  QUADRUPEDS use their voices for various purposes, as a signal of
danger, as a call from one member of a troop to another, or from the
mother to her lost offspring, or from the latter for protection to
their mother; but such uses need not here be considered. We are
concerned only with the difference between the voices of the sexes,
for instance between that of the lion and lioness, or of the bull
and cow. Almost all male animals use their voices much more during the
rutting-season than at any other time; and some, as the giraffe and
porcupine,* are said to be completely mute excepting at this season.
As the throats (i.e. the larynx and thyroid bodies*(2)) of stags
periodically become enlarged at the beginning of the
breeding-season, it might be thought that their powerful voices must
be somehow of high importance to them; but this is very doubtful. From
information given to me by two experienced observers, Mr. McNeill
and Sir P. Egerton, it seems that young stags under three years old do
not roar or bellow; and that the old ones begin bellowing at the
commencement of the breeding-season, at first only occasionally and
moderately, whilst they restlessly wander about in search of the
females. Their battles are prefaced by loud and prolonged bellowing,
but during the actual conflict they are silent. Animals of all kinds
which habitually use their voices utter various noises under any
strong emotion, as when enraged and preparing to fight; but this may
merely be the result of nervous excitement, which leads to the
spasmodic contraction of almost all the muscles of the body, as when a
man grinds his teeth and clenches his fists in rage or agony. No doubt
stags challenge each other to mortal combat by bellowing; but those
with the more powerful voices, unless at the same time the stronger,
better-armed, and more courageous, would not gain any advantage over
their rivals.

  * Owen, Anatomy of Vertebrates, vol. iii., p. 585.
  *(2) Ibid., p. 595.

  It is possible that the roaring of the lion may be of some service
to him by striking terror into his adversary; for when enraged he
likewise erects his mane and thus instinctively tries to make
himself appear as terrible as possible. But it can hardly be
supposed that the bellowing of the stag, even if it be of service to
him in this way, can have been important enough to have led to the
periodical enlargement of the throat. Some writers suggest that the
bellowing serves as a call to the female; but the experienced
observers above quoted inform me that female deer do not search for
the male, though the males search eagerly for the females, as indeed
might be expected from what we know of the habits of other male
quadrupeds. The voice of the female, on the other hand, quickly brings
to her one or more stags,* as is well known to the hunters who in wild
countries imitate her cry. If we could believe that the male had the
power to excite or allure the female by his voice, the periodical
enlargement of his vocal organs would be intelligible on the principle
of sexual selection, together with inheritance limited to the same sex
and season; but we have no evidence in favour of this view. As the
case stands, the loud voice of the stag during the breeding-season
does not seem to be of any special service to him, either during his
courtship or battles, or in any other way. But may we not believe that
the frequent use of the voice, under the strong excitement of love,
jealousy, and rage, continued during many generations, may at last
have produced an inherited effect on the vocal organs of the stag,
as well as of other male animals;, This appears to me, in our
present state of knowledge, the most probable view.

  * See, for instance, Major W. Ross King (The Sportsman in Canada,
1866, pp. 53, 131) on the habits of the moose and wild reindeer.

  The voice of the adult male gorilla is tremendous, and he is
furnished with a laryngeal sack, as is the adult male orang.* The
gibbons rank among the noisiest of monkeys, and the Sumatra species
(Hylobates syndactylus) is also furnished with an air sack; but Mr.
Blyth, who has had opportunities for observation, does not believe
that the male is noisier than the female. Hence, these latter
monkeys probably use their voices as a mutual call; and this is
certainly the case with some quadrupeds, for instance the
beaver.*(2) Another gibbon, the H. agilis, is remarkable, from
having the power of giving a complete and correct octave of musical
notes,*(3) which we may reasonably suspect serves as a sexual charm;
but I shall have to recur to this subject in the next chapter. The
vocal organs of the American Mycetes caraya are one-third larger in
the male than in the female, and are wonderfully powerful. These
monkeys in warm weather make the forests resound at morning and
evening with their overwhelming voices. The males begin the dreadful
concert, and often continue it during many hours, the females
sometimes joining in with their less powerful voices. An excellent
observer, Rengger,*(4) could not perceive that they were excited to
begin by any special cause; he thinks that, like many birds, they
delight in their own music, and try to excel each other. Whether
most of the foregoing monkeys have acquired their powerful voices in
order to beat their rivals and charm the females- or whether the vocal
organs have been strengthened and enlarged through the inherited
effects of long-continued use without any particular good being thus
gained- I will not pretend to say; but the former view, at least in
the case of the Hylobates agilis, seems the most probable.

  * Owen Anatomy of Vertebrates, vol. iii., p. 600.
  *(2) Mr. Green, in Journal of Linnean Society, vol. x., Zoology,
1869, note 362.
  *(3) C. L. Martin, General Introduction to the Natural History of
Mamm. Animals, 1841, p. 431.
  *(4) Naturgeschichte der Saugethiere von Paraguay, 1830, ss. 15, 21.

  I may here mention two very curious sexual peculiarities occurring
in seals, because they have been supposed by some writers to affect
the voice. The nose of the male sea-elephant (Macrorhinus
proboscideus) becomes greatly elongated during the breeding-season,
and can then be erected. In this state it is sometimes a foot in
length. The female is not thus provided at any period of life. The
male makes a wild, hoarse, gurgling noise, which is audible at a great
distance and is believed to be strengthened by the proboscis; the
voice of the female being different. Lesson compares the **** of
the proboscis, with the swelling of the wattles of male gallinaceous
birds whilst courting the females. In another allied kind of seal, the
bladder-nose (Cystophora cristata), the head is covered by a great
hood or bladder. This supported by the septum of the nose, which is
produced far backwards and rises into an internal crest seven inches
in height. The hood is clothed with short hair, and is muscular; can
be inflated until it more than equals the whole head in size! The
males when rutting, fight furiously on the ice, and their roaring
"is said to be sometimes so loud as to be heard four miles off."
When attacked they likewise roar or bellow; and whenever irritated the
bladder is inflated and quivers. Some naturalists believe that the
voice is thus strengthened, but various other uses have been
assigned to this extraordinary structure. Mr. R. Brown thinks that
it serves as a protection against accidents of all kinds; but this
is not probable, for, as I am assured by Mr. Lamont who killed 600
of these animals, the hood is rudimentary in the females, and it is
not developed in the males during youth.*

  * On the sea-elephant, see an article by Lesson, in Dict. Class.
Hist. Nat., tom. xiii., p. 418. For the Cystophora, or Stemmatopus,
see Dr. Dekay, Annals of Lyceum of Nat. Hist., New York, vol. i.,
1824, p. 94. Pennant has also collected information from the sealers
on this animal. The fullest account is given by Mr. Brown, in Proc.
Zoolog. Soc., 1868, p. 435.

  Odour.- With some animals, as with the notorious skunk of America,
the overwhelming odour which they emit appears to serve exclusively as
a defence. With shrew-mice (Sorex) both sexes possess abdominal
scent-glands and there can be little doubt, from the rejection of
their bodies by birds and beasts of prey, that the odour is
protective; nevertheless, the glands become enlarged in the males
during the breeding-season. In many other quadrupeds the glands are of
the same size in both sexes,* but their uses are not known. In other
species the glands are confined to the males, or are more developed
than in the females; and they almost always become more active
during the rutting-season. At this period the glands on the sides of
the face of the male elephant enlarge, and emit a secretion having a
strong musky odour. The males, and rarely the females, of many kinds
of bats have glands and protrudable sacks situated in various parts;
and it is believed that these are odoriferous.

  * As with the castoreum of the beaver, see Mr. L. H. Morgan's most
interesting work, The American Beaver, 1868, p. 300. Pallas (Spic.
Zoolog., fasc. viii., 1779, p. 23) has well discussed the
odoriferous glands of mammals. Owen (Anat. of Vertebrates, vol.
iii., p. 634) also gives an account of these glands, including those
of the elephant, and (p. 763) those of shrew-mice. On bats, Mr.
Dobson, Proceedings of the Zoological Society. 1873, p. 241.

  The rank effluvium of the male goat is well known, and that of
certain male deer is wonderfully strong and persistent. On the banks
of the Plata I perceived the air tainted with the odour of the male
Cervus campestris, at half a mile to leeward of a herd; and a silk
handkerchief, in which I carried home a skin, though often used and
washed, retained, when first unfolded, traces of the odour for one
year and seven months. This animal does not emit its strong odour
until more than a year old, and if castrated whilst young never
emits it.* Besides the general odour, permeating the whole body of
certain ruminants (for instance Bos moschatus) in the breeding-season,
many deer, antelopes, sheep, and goats possess odoriferous glands in
various situations, more especially on their faces. The so-called
tear-sacks, or suborbital pits, come under this head. These glands
secrete a semi-fluid fetid matter which is sometimes so copious as
to stain the whole face, as I have myself seen in an antelope. They
are "usually larger in the male than in the female, and their
development is checked by castration."*(2) According to Desmarest they
are altogether absent in the female of Antilope subgutturosa. Hence,
there can be no doubt that they stand in close relation with the
reproductive functions. They are also sometimes present, and sometimes
absent, in nearly allied forms. In the adult male musk-deer (Moschus
moschiferus), a naked space round the tail is bedewed with an
odoriferous fluid, whilst in the adult female, and in the male until
two years old, this space is covered with hair and is not odoriferous.
The proper musk-sack of this deer is from its position necessarily
confined to the male, and forms an additional scent-organ. It is a
singular fact that the matter secreted by this latter gland, does not,
according to Pallas, change in consistence, or increase in quantity,
during the rutting-season; nevertheless this naturalist admits that
its presence is in some way connected with the act of reproduction. He
gives, however, only a conjectural and unsatisfactory explanation of
its use.*(3)

  * Rengger, Naturgeschichte der Saugethiere von Paraguay, 1830, s.
355. This observer also gives some curious particulars in regard to
the odour.
  *(2) Owen, Anatomy of Vertebrates, vol. iii., p. 632. See also Dr.
Murie's observations on those glands in the Proc. Zoolog. Soc.,
1870, p. 340. Desmarest, "On the Antilope subgutturosa," Mammalogie,
1820, p. 455.
  *(3) Pallas, Spicilegia Zoolog., fasc. xiii., 1779, p. 24;
Desmoulins, Dict. Class. d'Hist. Nat., tom. iii., p. 586.

  In most cases, when only the male emits a strong odour during the
breeding-season, it probably serves to excite or allure the female. We
must not judge on this head by our own taste, for it is well known
that rats are enticed by certain essential oils, and cats by valerian,
substances far from agreeable to us; and that dogs, though they will
not eat carrion, sniff and roll on it. From the reasons given when
discussing the voice of the stag, we may reject the idea that the
odour serves to bring the females from a distance to the males. Active
and long-continued use cannot here have come into play, as in the case
of the vocal organs. The odour emitted must be of considerable
importance to the male, inasmuch as large and complex glands,
furnished with muscles for everting the sack, and for closing or
opening the orifice, have in some cases been developed. The
development of these organs is intelligible through sexual
selection, if the most odoriferous males are the most successful in
winning the females, and in leaving offspring to inherit their
gradually perfected glands and odours.
  Development of the Hair.- We have seen that male quadrupeds often
have the hair on their necks and shoulders much more developed than
the females; and many additional instances could be given. This
sometimes serves as a defence to the male during his battles; but
whether the hair in most cases has been specially developed for this
purpose, is very doubtful. We may feel almost certain that this is not
the case, when only a thin and narrow crest runs along the back; for a
crest of this kind would afford scarcely any protection, and the ridge
of the back is not a place likely to be injured; nevertheless such
crests are sometimes confined to the males, or are much more developed
in them than in the females. Two antelopes, the Tragelaphus
scriptus* (see fig. 70) and Portax picta may be given as instances.
When stags, and the males of the wild goat, are enraged or
terrified, these crests stand erect;*(2) but it cannot be supposed
that they have been developed merely for the sake of exciting fear
in their enemies. One of the above-named antelopes, the Portax
picta, has a large well-defined brush of black hair on the throat, and
this is much larger in the male than in the female. In the
Ammotragus tragelaphus of north Africa, a member of the
sheep-family, the fore-legs are almost concealed by an extraordinary
growth of hair, which depends from the neck and upper halves of the
legs; but Mr. Bartlett does not believe that this mantle is of the
least use to the male, in whom it is much more developed than in the

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