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Chapter XVII
GALAPAGOS ARCHIPELAGO.
(PLATE 79. TESTUDO ABINGDONII, GALAPAGOS ISLANDS.)
The whole group volcanic.
Number of craters.
Leafless bushes.
Colony at Charles Island.
James Island.
Salt-lake in crater.
Natural history of the group.
Ornithology, curious finches.
Reptiles.
Great tortoises, habits of.
Marine Lizard, feeds on Sea-weed.
Terrestrial Lizard, burrowing habits, herbivorous.
Importance of reptiles in the Archipelago.
Fish, shells, insects.
Botany.
American type of organisation.
Differences in the species or races on different islands.
Tameness of the birds.
Fear of man an acquired instinct.
SEPTEMBER 15, 1835.
(PLATE 80. GALAPAGOS ARCHIPELAGO.)
This archipelago consists of ten principal islands, of which five
exceed the others in size. They are situated under the Equator, and
between five and six hundred miles westward of the coast of
America. They are all formed of volcanic rocks; a few fragments of
granite curiously glazed and altered by the heat can hardly be
considered as an exception. Some of the craters surmounting the
larger islands are of immense size, and they rise to a height of
between three and four thousand feet. Their flanks are studded by
innumerable smaller orifices. I scarcely hesitate to affirm that
there must be in the whole archipelago at least two thousand
craters. These consist either of lava and scoriae, or of
finely-stratified, sandstone-like tuff. Most of the latter are
beautifully symmetrical; they owe their origin to eruptions of
volcanic mud without any lava: it is a remarkable circumstance that
every one of the twenty-eight tuff-craters which were examined had
their southern sides either much lower than the other sides, or
quite broken down and removed. As all these craters apparently have
been formed when standing in the sea, and as the waves from the
trade wind and the swell from the open Pacific here unite their
forces on the southern coasts of all the islands, this singular
uniformity in the broken state of the craters, composed of the soft
and yielding tuff, is easily explained.
Considering that these islands are placed directly under the
equator, the climate is far from being excessively hot; this seems
chiefly caused by the singularly low temperature of the surrounding
water, brought here by the great southern Polar current. Excepting
during one short season very little rain falls, and even then it is
irregular; but the clouds generally hang low. Hence, whilst the
lower parts of the islands are very sterile, the upper parts, at a
height of a thousand feet and upwards, possess a damp climate and a
tolerably luxuriant vegetation. This is especially the case on the
windward sides of the islands, which first receive and condense the
moisture from the atmosphere.
In the morning (17th) we landed on Chatham Island, which, like the
others, rises with a tame and rounded outline, broken here and
there by scattered hillocks, the remains of former craters. Nothing
could be less inviting than the first appearance. A broken field of
black basaltic lava, thrown into the most rugged waves, and crossed
by great fissures, is everywhere covered by stunted, sunburnt
brushwood, which shows little signs of life. The dry and parched
surface, being heated by the noonday sun, gave to the air a close
and sultry feeling, like that from a stove: we fancied even that
the bushes smelt unpleasantly. Although I diligently tried to
collect as many plants as possible, I succeeded in getting very
few; and such wretched-looking little weeds would have better
become an arctic than an equatorial Flora. The brushwood appears,
from a short distance, as leafless as our trees during winter; and
it was some time before I discovered that not only almost every
plant was now in full leaf, but that the greater number were in
flower. The commonest bush is one of the Euphorbiaceae: an acacia
and a great odd-looking cactus are the only trees which afford any
shade. After the season of heavy rains, the islands are said to
appear for a short time partially green. The volcanic island of
Fernando Noronha, placed in many respects under nearly similar
conditions, is the only other country where I have seen a
vegetation at all like this of the Galapagos Islands.
The "Beagle" sailed round Chatham Island, and anchored in several
bays. One night I slept on shore on a part of the island where
black truncated cones were extraordinarily numerous: from one small
eminence I counted sixty of them, all surmounted by craters more or
less perfect. The greater number consisted merely of a ring of red
scoriae or slags cemented together: and their height above the
plain of lava was not more than from fifty to a hundred feet: none
had been very lately active. The entire surface of this part of the
island seems to have been permeated, like a sieve, by the
subterranean vapours: here and there the lava, whilst soft, has
been blown into great bubbles; and in other parts, the tops of
caverns similarly formed have fallen in, leaving circular pits with
steep sides. From the regular form of the many craters, they gave
to the country an artificial appearance, which vividly reminded me
of those parts of Staffordshire where the great iron-foundries are
most numerous. The day was glowing hot, and the scrambling over the
rough surface and through the intricate thickets was very
fatiguing; but I was well repaid by the strange Cyclopean scene. As
I was walking along I met two large tortoises, each of which must
have weighed at least two hundred pounds: one was eating a piece of
cactus, and as I approached, it stared at me and slowly walked
away; the other gave a deep hiss, and drew in its head. These huge
reptiles, surrounded by the black lava, the leafless shrubs, and
large cacti, seemed to my fancy like some antediluvian animals. The
few dull-coloured birds cared no more for me than they did for the
great tortoises.
SEPTEMBER 23, 1835.
The "Beagle" proceeded to Charles Island. This archipelago has long
been frequented, first by the Bucaniers, and latterly by whalers,
but it is only within the last six years that a small colony has
been established here. The inhabitants are between two and three
hundred in number; they are nearly all people of colour, who have
been banished for political crimes from the Republic of the
Equator, of which Quito is the capital. The settlement is placed
about four and a half miles inland, and at a height probably of a
thousand feet. In the first part of the road we passed through
leafless thickets, as in Chatham Island. Higher up the woods
gradually became greener; and as soon as we crossed the ridge of
the island we were cooled by a fine southerly breeze, and our sight
refreshed by a green and thriving vegetation. In this upper region
coarse grasses and ferns abound; but there are no tree-ferns: I saw
nowhere any member of the Palm family, which is the more singular,
as 360 miles northward, Cocos Island takes its name from the number
of cocoa-nuts. The houses are irregularly scattered over a flat
space of ground, which is cultivated with sweet potatoes and
bananas. It will not easily be imagined how pleasant the sight of
black mud was to us, after having been so long accustomed to the
parched soil of Peru and Northern Chile. The inhabitants, although
complaining of poverty, obtain, without much trouble, the means of
subsistence. In the woods there are many wild pigs and goats; but
the staple article of animal food is supplied by the tortoises.
Their numbers have of course been greatly reduced in this island,
but the people yet count on two days' hunting giving them food for
the rest of the week. It is said that formerly single vessels have
taken away as many as seven hundred, and that the ship's company of
a frigate some years since brought down in one day two hundred
tortoises to the beach.
SEPTEMBER 29, 1835.
We doubled the south-west extremity of Albemarle Island, and the
next day were nearly becalmed between it and Narborough Island.
Both are covered with immense deluges of black naked lava, which
have flowed either over the rims of the great caldrons, like pitch
over the rim of a pot in which it has been boiled, or have burst
forth from smaller orifices on the flanks; in their descent they
have spread over miles of the sea-coast. On both of these islands
eruptions are known to have taken place; and in Albemarle we saw a
small jet of smoke curling from the summit of one of the great
craters. In the evening we anchored in Bank's Cove, in Albemarle
Island. The next morning I went out walking. To the south of the
broken tuff-crater, in which the "Beagle" was anchored, there was
another beautifully symmetrical one of an elliptic form; its longer
axis was a little less than a mile, and its depth about 500 feet.
At its bottom there was a shallow lake, in the middle of which a
tiny crater formed an islet. The day was overpoweringly hot, and
the lake looked clear and blue: I hurried down the cindery slope,
and, choked with dust, eagerly tasted the water--but, to my sorrow,
I found it salt as brine.
The rocks on the coast abounded with great black lizards, between
three and four feet long; and on the hills, an ugly yellowish-brown
species was equally common. We saw many of this latter kind, some
clumsily running out of the way, and others shuffling into their
burrows. I shall presently describe in more detail the habits of
both these reptiles. The whole of this northern part of Albemarle
Island is miserably sterile.
OCTOBER 8, 1835.
We arrived at James Island: this island, as well as Charles Island,
were long since thus named after our kings of the Stuart line. Mr.
Bynoe, myself, and our servants were left here for a week, with
provisions and a tent, whilst the "Beagle" went for water. We found
here a party of Spaniards who had been sent from Charles Island to
dry fish and to salt tortoise-meat. About six miles inland and at
the height of nearly 2000 feet, a hovel had been built in which two
men lived, who were employed in catching tortoises, whilst the
others were fishing on the coast. I paid this party two visits, and
slept there one night. As in the other islands, the lower region
was covered by nearly leafless bushes, but the trees were here of a
larger growth than elsewhere, several being two feet and some even
two feet nine inches in diameter. The upper region, being kept damp
by the clouds, supports a green and flourishing vegetation. So damp
was the ground, that there were large beds of a coarse cyperus, in
which great numbers of a very small water-rail lived and bred.
While staying in this upper region, we lived entirely upon
tortoise-meat: the breast-plate roasted (as the Gauchos do carne
con cuero), with the flesh on it, is very good; and the young
tortoises make excellent soup; but otherwise the meat to my taste
is indifferent.
One day we accompanied a party of the Spaniards in their whale-boat
to a salina, or lake from which salt is procured. After landing we
had a very rough walk over a rugged field of recent lava, which has
almost surrounded a tuff-crater at the bottom of which the
salt-lake lies. The water is only three or four inches deep and
rests on a layer of beautifully crystallised, white salt. The lake
is quite circular, and is fringed with a border of bright green
succulent plants; the almost precipitous walls of the crater are
clothed with wood, so that the scene was altogether both
picturesque and curious. A few years since the sailors belonging to
a sealing-vessel murdered their captain in this quiet spot; and we
saw his skull lying among the bushes.
During the greater part of our stay of a week the sky was
cloudless, and if the trade-wind failed for an hour the heat became
very oppressive. On two days the thermometer within the tent stood
for some hours at 93 degrees; but in the open air, in the wind and
sun, at only 85 degrees. The sand was extremely hot; the
thermometer placed in some of a brown colour immediately rose to
137 degrees, and how much above that it would have risen I do not
know for it was not graduated any higher. The black sand felt much
hotter, so that even in thick boots it was quite disagreeable to
walk over it.
The natural history of these islands is eminently curious, and well
deserves attention. Most of the organic productions are aboriginal
creations found nowhere else; there is even a difference between
the inhabitants of the different islands; yet all show a marked
relationship with those of America, though separated from that
continent by an open space of ocean, between 500 and 600 miles in
width. The archipelago is a little world within itself, or rather a
satellite attached to America, whence it has derived a few stray
colonists, and has received the general character of its indigenous
productions. Considering the small size of these islands, we feel
the more astonished at the number of their aboriginal beings, and
at their confined range. Seeing every height crowned with its
crater, and the boundaries of most of the lava-streams still
distinct, we are led to believe that within a period geologically
recent the unbroken ocean was here spread out. Hence, both in space
and time, we seem to be brought somewhat near to that great
fact--that mystery of mysteries--the first appearance of new beings
on this earth.
Of terrestrial mammals there is only one which must be considered
as indigenous, namely a mouse (Mus Galapagoensis) and this is
confined, as far as I could ascertain, to Chatham Island, the most
easterly island of the group. It belongs, as I am informed by Mr.
Waterhouse, to a division of the family of mice characteristic of
America. At James Island there is a rat sufficiently distinct from
the common kind to have been named and described by Mr. Waterhouse;
but as it belongs to the old-world division of the family, and as
this island has been frequented by ships for the last hundred and
fifty years, I can hardly doubt that this rat is merely a variety
produced by the new and peculiar climate, food, and soil, to which
it has been subjected. Although no one has a right to speculate
without distinct facts, yet even with respect to the Chatham Island
mouse, it should be borne in mind that it may possibly be an
American species imported here; for I have seen, in a most
unfrequented part of the Pampas, a native mouse living in the roof
of a newly built hovel, and therefore its transportation in a
vessel is not improbable: analogous facts have been observed by Dr.
Richardson in North America.
Of land-birds I obtained twenty-six kinds, all peculiar to the
group and found nowhere else, with the exception of one lark-like
finch from North America (Dolichonyx oryzivorus) which ranges on
that continent as far north as 54 degrees, and generally frequents
marshes. The other twenty-five birds consist, firstly, of a hawk,
curiously intermediate in structure between a Buzzard and the
American group of carrion-feeding Polybori; and with these latter
birds it agrees most closely in every habit and even tone of voice.
Secondly there are two owls, representing the short-eared and white
barn-owls of Europe. Thirdly a wren, three tyrant-flycatchers (two
of them species of Pyrocephalus, one or both of which would be
ranked by some ornithologists as only varieties), and a dove--all
analogous to, but distinct from, American species. Fourthly a
swallow, which though differing from the Progne purpurea of both
Americas, only in being rather duller coloured, smaller, and
slenderer, is considered by Mr. Gould as specifically distinct.
Fifthly there are three species of mocking-thrush--a form highly
characteristic of America. The remaining land-birds form a most
singular group of finches, related to each other in the structure
of their beaks, short tails, form of body and plumage: there are
thirteen species which Mr. Gould has divided into four sub-groups.
All these species are peculiar to this archipelago; and so is the
whole group, with the exception of one species of the sub-group
Cactornis, lately brought from Bow Island, in the Low Archipelago.
Of Cactornis the two species may be often seen climbing about the
flowers of the great cactus-trees; but all the other species of
this group of finches, mingled together in flocks, feed on the dry
and sterile ground of the lower districts. The males of all, or
certainly of the greater number, are jet black; and the females
(with perhaps one or two exceptions) are brown.
(PLATE 81. FINCHES FROM GALAPAGOS ARCHIPELAGO. 1. Geospiza
magnirostris. 2. Geospiza fortis. 3. Geospiza parvula. 4. Certhidea
olivasea.)
The most curious fact is the perfect gradation in the size of the
beaks in the different species of Geospiza, from one as large as
that of a hawfinch to that of a chaffinch, and (if Mr. Gould is
right in including his sub-group, Certhidea, in the main group)
even to that of a warbler. The largest beak in the genus Geospiza
is shown in (Plate 81) Figure 1, and the smallest in Figure 3; but
instead of there being only one intermediate species, with a beak
of the size shown in Figure 2, there are no less than six species
with insensibly graduated beaks. The beak of the sub-group
Certhidea, is shown in Figure 4. The beak of Cactornis is somewhat
like that of a starling, and that of the fourth sub-group,
Camarhynchus, is slightly parrot-shaped. Seeing this gradation and
diversity of structure in one small, intimately related group of
birds, one might really fancy that from an original paucity of
birds in this archipelago, one species had been taken and modified
for different ends. In a like manner it might be fancied that a
bird, originally a buzzard, had been induced here to undertake the
office of the carrion-feeding Polybori of the American continent.
Of waders and water-birds I was able to get only eleven kinds, and
of these only three (including a rail confined to the damp summits
of the islands) are new species. Considering the wandering habits
of the gulls, I was surprised to find that the species inhabiting
these islands is peculiar, but allied to one from the southern
parts of South America. The far greater peculiarity of the
land-birds, namely, twenty-five out of twenty-six being new
species, or at least new races, compared with the waders and
web-footed birds, is in accordance with the greater range which
these latter orders have in all parts of the world. We shall
hereafter see this law of aquatic forms, whether marine or fresh
water, being less peculiar at any given point of the earth's
surface than the terrestrial forms of the same classes, strikingly
illustrated in the shells, and in a lesser degree in the insects of
this archipelago.
Two of the waders are rather smaller than the same species brought
from other places: the swallow is also smaller, though it is
doubtful whether or not it is distinct from its analogue. The two
owls, the two tyrant-flycatchers (Pyrocephalus) and the dove, are
also smaller than the analogous but distinct species, to which they
are most nearly related; on the other hand, the gull is rather
larger. The two owls, the swallow, all three species of
mocking-thrush, the dove in its separate colours though not in its
whole plumage, the Totanus, and the gull, are likewise duskier
coloured than their analogous species; and in the case of the
mocking-thrush and Totanus, than any other species of the two
genera. With the exception of a wren with a fine yellow breast, and
of a tyrant-flycatcher with a scarlet tuft and breast, none of the
birds are brilliantly coloured, as might have been expected in an
equatorial district. Hence it would appear probable that the same
causes which here make the immigrants of some species smaller, make
most of the peculiar Galapageian species also smaller, as well as
very generally more dusky coloured. All the plants have a wretched,
weedy appearance, and I did not see one beautiful flower. The
insects, again, are small-sized and dull coloured, and, as Mr.
Waterhouse informs me, there is nothing in their general appearance
which would have led him to imagine that they had come from under
the equator. (17/1. The progress of research has shown that some of
these birds, which were then thought to be confined to the islands,
occur on the American continent. The eminent ornithologist, Mr.
Sclater, informs me that this is the case with the Strix
punctatissima and Pyrocephalus nanus; and probably with the Otus
galapagoensis and Zenaida galapagoensis: so that the number of
endemic birds is reduced to twenty-three, or probably to
twenty-one. Mr. Sclater thinks that one or two of these endemic
forms should be ranked rather as varieties than species, which
always seemed to me probable.) The birds, plants, and insects have
a desert character, and are not more brilliantly coloured than
those from southern Patagonia; we may, therefore, conclude that the
usual gaudy colouring of the intertropical productions is not
related either to the heat or light of those zones, but to some
other cause, perhaps to the conditions of existence being generally
favourable to life.
We will now turn to the order of reptiles, which gives the most
striking character to the zoology of these islands. The species are
not numerous, but the numbers of individuals of each species are
extraordinarily great. There is one small lizard belonging to a
South American genus, and two species (and probably more) of the
Amblyrhynchus--a genus confined to the Galapagos Islands. There is
one snake which is numerous; it is identical, as I am informed by
M. Bibron, with the Psammophis Temminckii from Chile. (17/2. This
is stated by Dr. Gunther "Zoological Society" January 24, 1859, to
be a peculiar species, not known to inhabit any other country.) Of
sea-turtle I believe there are more than one species, and of
tortoises there are, as we shall presently show, two or three
species or races. Of toads and frogs there are none: I was
surprised at this, considering how well suited for them the
temperate and damp upper woods appeared to be. It recalled to my
mind the remark made by Bory St. Vincent, namely, that none of this
family are found on any of the volcanic islands in the great
oceans. (17/3. "Voyage aux Quatres Iles d'Afrique." With respect to
the Sandwich Islands see Tyerman and Bennett's "Journal" volume 1
page 434. For Mauritius see "Voyage par un Officier" etc. Part 1
page 170. There are no frogs in the Canary Islands, Webb et
Berthelot "Hist. Nat. des Iles Canaries." I saw none at St. Jago in
the Cape de Verds. There are none at St. Helena.) As far as I can
ascertain from various works, this seems to hold good throughout
the Pacific, and even in the large islands of the Sandwich
archipelago. Mauritius offers an apparent exception, where I saw
the Rana Mascariensis in abundance: this frog is said now to
inhabit the Seychelles, Madagascar, and Bourbon; but on the other
hand, Du Bois, in his voyage in 1669, states that there were no
reptiles in Bourbon except tortoises; and the Officier du Roi
asserts that before 1768 it had been attempted, without success, to
introduce frogs into Mauritius--I presume for the purpose of
eating: hence it may be well doubted whether this frog is an
aboriginal of these islands. The absence of the frog family in the
oceanic islands is the more remarkable, when contrasted with the
case of lizards, which swarm on most of the smallest islands. May
this difference not be caused by the greater facility with which
the eggs of lizards, protected by calcareous shells, might be
transported through salt-water, than could the slimy spawn of
frogs?
I will first describe the habits of the tortoise (Testudo nigra,
formerly called Indica), which has been so frequently alluded to.
These animals are found, I believe, on all the islands of the
Archipelago; certainly on the greater number. They frequent in
preference the high damp parts, but they likewise live in the lower
and arid districts. I have already shown, from the numbers which
have been caught in a single day, how very numerous they must be.
Some grow to an immense size: Mr. Lawson, an Englishman, and
vice-governor of the colony, told us that he had seen several so
large that it required six or eight men to lift them from the
ground; and that some had afforded as much as two hundred pounds of
meat. The old males are the largest, the females rarely growing to
so great a size: the male can readily be distinguished from the
female by the greater length of its tail. The tortoises which live
on those islands where there is no water, or in the lower and arid
parts of the others, feed chiefly on the succulent cactus. Those
which frequent the higher and damp regions eat the leaves of
various trees, a kind of berry (called guayavita) which is acid and
austere, and likewise a pale green filamentous lichen (Usnera
plicata), that hangs from the boughs of the trees.
The tortoise is very fond of water, drinking large quantities, and
wallowing in the mud. The larger islands alone possess springs, and
these are always situated towards the central parts, and at a
considerable height. The tortoises, therefore, which frequent the
lower districts, when thirsty, are obliged to travel from a long
distance. Hence broad and well-beaten paths branch off in every
direction from the wells down to the sea-coast; and the Spaniards,
by following them up, first discovered the watering-places. When I
landed at Chatham Island, I could not imagine what animal travelled
so methodically along well-chosen tracks. Near the springs it was a
curious spectacle to behold many of these huge creatures, one set
eagerly travelling onwards with outstretched necks, and another set
returning, after having drunk their fill. When the tortoise arrives
at the spring, quite regardless of any spectator, he buries his
head in the water above his eyes, and greedily swallows great
mouthfuls, at the rate of about ten in a minute. The inhabitants
say each animal stays three or four days in the neighbourhood of
the water, and then returns to the lower country; but they differed
respecting the frequency of these visits. The animal probably
regulates them according to the nature of the food on which it has
lived. It is, however, certain that tortoises can subsist even on
those islands where there is no other water than what falls during
a few rainy days in the year.
I believe it is well ascertained that the bladder of the frog acts
as a reservoir for the moisture necessary to its existence: such
seems to be the case with the tortoise. For some time after a visit
to the springs, their urinary bladders are distended with fluid,
which is said gradually to decrease in volume, and to become less
pure. The inhabitants, when walking in the lower district, and
overcome with thirst, often take advantage of this circumstance,
and drink the contents of the bladder if full: in one I saw killed,
the fluid was quite limpid, and had only a very slightly bitter
taste. The inhabitants, however, always first drink the water in
the pericardium, which is described as being best.
The tortoises, when purposely moving towards any point, travel by
night and day and arrive at their journey's end much sooner than
would be expected. The inhabitants, from observing marked
individuals, consider that they travel a distance of about eight
miles in two or three days. One large tortoise, which I watched,
walked at the rate of sixty yards in ten minutes, that is 360 yards
in the hour, or four miles a day,--allowing a little time for it to
eat on the road. During the breeding season, when the male and
female are together, the male utters a hoarse roar or bellowing,
which, it is said, can be heard at the distance of more than a
hundred yards. The female never uses her voice, and the male only
at these times; so that when the people hear this noise, they know
that the two are together. They were at this time (October) laying
their eggs. The female, where the soil is sandy, deposits them
together, and covers them up with sand; but where the ground is
rocky she drops them indiscriminately in any hole: Mr. Bynoe found
seven placed in a fissure. The egg is white and spherical; one
which I measured was seven inches and three-eighths in
circumference, and therefore larger than a hen's egg. The young
tortoises, as soon as they are hatched, fall a prey in great
numbers to the carrion-feeding buzzard. The old ones seem generally
to die from accidents, as from falling down precipices: at least,
several of the inhabitants told me that they never found one dead
without some evident cause.
The inhabitants believe that these animals are absolutely deaf;
certainly they do not overhear a person walking close behind them.
I was always amused when overtaking one of these great monsters, as
it was quietly pacing along, to see how suddenly, the instant I
passed, it would draw in its head and legs, and uttering a deep
hiss fall to the ground with a heavy sound, as if struck dead. I
frequently got on their backs, and then giving a few raps on the
hinder part of their shells, they would rise up and walk away;--but
I found it very difficult to keep my balance. The flesh of this
animal is largely employed, both fresh and salted; and a
beautifully clear oil is prepared from the fat. When a tortoise is
caught, the man makes a slit in the skin near its tail, so as to
see inside its body, whether the fat under the dorsal plate is
thick. If it is not, the animal is liberated; and it is said to
recover soon from this strange operation. In order to secure the
tortoises, it is not sufficient to turn them like turtle, for they
are often able to get on their legs again.
There can be little doubt that this tortoise is an aboriginal
inhabitant of the Galapagos; for it is found on all, or nearly all,
the islands, even on some of the smaller ones where there is no
water; had it been an imported species this would hardly have been
the case in a group which has been so little frequented. Moreover,
the old Bucaniers found this tortoise in greater numbers even than
at present: Wood and Rogers also, in 1708, say that it is the
opinion of the Spaniards that it is found nowhere else in this
quarter of the world. It is now widely distributed; but it may be
questioned whether it is in any other place an aboriginal. The
bones of a tortoise at Mauritius, associated with those of the
extinct Dodo, have generally been considered as belonging to this
tortoise; if this had been so, undoubtedly it must have been there
indigenous; but M. Bibron informs me that he believes that it was
distinct, as the species now living there certainly is.
(PLATE 82. AMBLYRHYNCHUS CRISTATUS. a. Tooth of natural size, and
likewise magnified.)
The Amblyrhynchus, a remarkable genus of lizards, is confined to
this archipelago; there are two species, resembling each other in
general form, one being terrestrial and the other aquatic. This
latter species (A. cristatus) was first characterised by Mr. Bell,
who well foresaw, from its short, broad head, and strong claws of
equal length, that its habits of life would turn out very peculiar,
and different from those of its nearest ally, the Iguana. It is
extremely common on all the islands throughout the group, and lives
exclusively on the rocky sea-beaches, being never found, at least I
never saw one, even ten yards in-shore. It is a hideous-looking
creature, of a dirty black colour, stupid, and sluggish in its
movements. The usual length of a full-grown one is about a yard,
but there are some even four feet long; a large one weighed twenty
pounds: on the island of Albemarle they seem to grow to a greater
size than elsewhere. Their tails are flattened sideways, and all
four feet partially webbed. They are occasionally seen some hundred
yards from the shore, swimming about; and Captain Collnett, in his
Voyage says, "They go to sea in herds a-fishing, and sun themselves
on the rocks; and may be called alligators in miniature." It must
not, however, be supposed that they live on fish. When in the water
this lizard swims with perfect ease and quickness, by a serpentine
movement of its body and flattened tail--the legs being motionless
and closely collapsed on its sides. A seaman on board sank one,
with a heavy weight attached to it, thinking thus to kill it
directly; but when, an hour afterwards, he drew up the line, it was
quite active. Their limbs and strong claws are admirably adapted
for crawling over the rugged and fissured masses of lava which
everywhere form the coast. In such situations a group of six or
seven of these hideous reptiles may oftentimes be seen on the black
rocks, a few feet above the surf, basking in the sun with
outstretched legs.
I opened the stomachs of several, and found them largely distended
with minced sea-weed (Ulvae), which grows in thin foliaceous
expansions of a bright green or a dull red colour. I do not
recollect having observed this sea-weed in any quantity on the
tidal rocks; and I have reason to believe it grows at the bottom of
the sea, at some little distance from the coast. If such be the
case, the object of these animals occasionally going out to sea is
explained. The stomach contained nothing but the sea-weed. Mr.
Bynoe, however, found a piece of a crab in one; but this might have
got in accidentally, in the same manner as I have seen a
caterpillar, in the midst of some lichen, in the paunch of a
tortoise. The intestines were large, as in other herbivorous
animals. The nature of this lizard's food, as well as the structure
of its tail and feet, and the fact of its having been seen
voluntarily swimming out at sea, absolutely prove its aquatic
habits; yet there is in this respect one strange anomaly, namely,
that when frightened it will not enter the water. Hence it is easy
to drive these lizards down to any little point overhanging the
sea, where they will sooner allow a person to catch hold of their
tails than jump into the water. They do not seem to have any notion
of biting; but when much frightened they squirt a drop of fluid
from each nostril. I threw one several times as far as I could,
into a deep pool left by the retiring tide; but it invariably
returned in a direct line to the spot where I stood. It swam near
the bottom, with a very graceful and rapid movement, and
occasionally aided itself over the uneven ground with its feet. As
soon as it arrived near the edge, but still being under water, it
tried to conceal itself in the tufts of sea-weed, or it entered
some crevice. As soon as it thought the danger was past, it crawled
out on the dry rocks, and shuffled away as quickly as it could. I
several times caught this same lizard, by driving it down to a
point, and though possessed of such perfect powers of diving and
swimming, nothing would induce it to enter the water; and as often
as I threw it in, it returned in the manner above described.
Perhaps this singular piece of apparent stupidity may be accounted
for by the circumstance that this reptile has no enemy whatever on
shore, whereas at sea it must often fall a prey to the numerous
sharks. Hence, probably, urged by a fixed and hereditary instinct
that the shore is its place of safety, whatever the emergency may
be, it there takes refuge.
During our visit (in October) I saw extremely few small individuals
of this species, and none I should think under a year old. From
this circumstance it seems probable that the breeding season had
not then commenced. I asked several of the inhabitants if they knew
where it laid its eggs: they said that they knew nothing of its
propagation, although well acquainted with the eggs of the land
kind--a fact, considering how very common this lizard is, not a
little extraordinary.
We will now turn to the terrestrial species (A. Demarlii), with a
round tail, and toes without webs. This lizard, instead of being
found like the other on all the islands, is confined to the central
part of the archipelago, namely to Albemarle, James, Barrington,
and Indefatigable islands. To the southward, in Charles, Hood, and
Chatham Islands, and to the northward, in Towers, Bindloes, and
Abingdon, I neither saw nor heard of any. It would appear as if it
had been created in the centre of the archipelago, and thence had
been dispersed only to a certain distance. Some of these lizards
inhabit the high and damp parts of the islands, but they are much
more numerous in the lower and sterile districts near the coast. I
cannot give a more forcible proof of their numbers, than by stating
that when we were left at James Island, we could not for some time
find a spot free from their burrows on which to pitch our single
tent. Like their brothers the sea-kind, they are ugly animals, of a
yellowish orange beneath, and of a brownish-red colour above: from
their low facial angle they have a singularly stupid appearance.
They are, perhaps, of a rather less size than the marine species;
but several of them weighed between ten and fifteen pounds. In
their movements they are lazy and half torpid. When not frightened,
they slowly crawl along with their tails and bellies dragging on
the ground. They often stop, and doze for a minute or two, with
closed eyes and hind legs spread out on the parched soil.
They inhabit burrows which they sometimes make between fragments of
lava, but more generally on level patches of the soft
sandstone-like tuff. The holes do not appear to be very deep, and
they enter the ground at a small angle; so that when walking over
these lizard-warrens, the soil is constantly giving way, much to
the annoyance of the tired walker. This animal, when making its
burrow, works alternately the opposite sides of its body. One front
leg for a short time scratches up the soil, and throws it towards
the hind foot, which is well placed so as to heave it beyond the
mouth of the hole. That side of the body being tired, the other
takes up the task, and so on alternately. I watched one for a long
time, till half its body was buried; I then walked up and pulled it
by the tail; at this it was greatly astonished, and soon shuffled
up to see what was the matter; and then stared me in the face, as
much as to say, "What made you pull my tail?"
They feed by day, and do not wander far from their burrows; if
frightened, they rush to them with a most awkward gait. Except when
running down hill, they cannot move very fast, apparently from the
lateral position of their legs. They are not at all timorous: when
attentively watching any one, they curl their tails, and, raising
themselves on their front legs, nod their heads vertically, with a
quick movement, and try to look very fierce; but in reality they
are not at all so: if one just stamps on the ground, down go their
tails, and off they shuffle as quickly as they can. I have
frequently observed small fly-eating lizards, when watching
anything, nod their heads in precisely the same manner; but I do
not at all know for what purpose. If this Amblyrhynchus is held and
plagued with a stick, it will bite it very severely; but I caught
many by the tail, and they never tried to bite me. If two are
placed on the ground and held together, they will fight, and bite
each other till blood is drawn.
The individuals, and they are the greater number, which inhabit the
lower country, can scarcely taste a drop of water throughout the
year; but they consume much of the succulent cactus, the branches
of which are occasionally broken off by the wind. I several times
threw a piece to two or three of them when together; and it was
amusing enough to see them trying to seize and carry it away in
their mouths, like so many hungry dogs with a bone. They eat very
deliberately, but do not chew their food. The little birds are
aware how harmless these creatures are: I have seen one of the
thick-billed finches picking at one end of a piece of cactus (which
is much relished by all the animals of the lower region), whilst a
lizard was eating at the other end; and afterwards the little bird
with the utmost indifference hopped on the back of the reptile.
I opened the stomachs of several, and found them full of vegetable
fibres and leaves of different trees, especially of an acacia. In
the upper region they live chiefly on the acid and astringent
berries of the guayavita, under which trees I have seen these
lizards and the huge tortoises feeding together. To obtain the
acacia-leaves they crawl up the low stunted trees; and it is not
uncommon to see a pair quietly browsing, whilst seated on a branch
several feet above the ground. These lizards, when cooked, yield a
white meat, which is liked by those whose stomachs soar above all
prejudices. Humboldt has remarked that in intertropical South
America all lizards which inhabit dry regions are esteemed
delicacies for the table. The inhabitants state that those which
inhabit the upper damp parts drink water, but that the others do
not, like the tortoises, travel up for it from the lower sterile
country. At the time of our visit, the females had within their
bodies numerous, large, elongated eggs, which they lay in their
burrows: the inhabitants seek them for food.
These two species of Amblyrhynchus agree, as I have already stated,
in their general structure, and in many of their habits. Neither
have that rapid movement, so characteristic of the genera Lacerta
and Iguana. They are both herbivorous, although the kind of
vegetation on which they feed is so very different. Mr. Bell has
given the name to the genus from the shortness of the snout:
indeed, the form of the mouth may almost be compared to that of the
tortoise: one is led to suppose that this is an adaptation to their
herbivorous appetites. It is very interesting thus to find a
well-characterised genus, having its marine and terrestrial
species, belonging to so confined a portion of the world. The
aquatic species is by far the most remarkable, because it is the
only existing lizard which lives on marine vegetable productions.
As I at first observed, these islands are not so remarkable for the
number of the species of reptiles, as for that of the individuals,
when we remember the well-beaten paths made by the thousands of
huge tortoises--the many turtles--the great warrens of the
terrestrial Amblyrhynchus--and the groups of the marine species
basking on the coast-rocks of every island--we must admit that
there is no other quarter of the world where this Order replaces
the herbivorous mammalia in so extraordinary a manner. The
geologist on hearing this will probably refer back in his mind to
the Secondary epochs, when lizards, some herbivorous, some
carnivorous, and of dimensions comparable only with our existing
whales, swarmed on the land and in the sea. It is, therefore,
worthy of his observation that this archipelago, instead of
possessing a humid climate and rank vegetation, cannot be
considered otherwise than extremely arid, and, for an equatorial
region, remarkably temperate.
To finish with the zoology: the fifteen kinds of sea-fish which I
procured here are all new species; they belong to twelve genera,
all widely distributed, with the exception of Prionotus, of which
the four previously known species live on the eastern side of
America. Of land-shells I collected sixteen kinds (and two marked
varieties) of which, with the exception of one Helix found at
Tahiti, all are peculiar to this archipelago: a single fresh-water
shell (Paludina) is common to Tahiti and Van Diemen's Land. Mr.
Cuming, before our voyage, procured here ninety species of
sea-shells, and this does not include several species not yet
specifically examined, of Trochus, Turbo, Monodonta, and Nassa. He
has been kind enough to give me the following interesting results:
of the ninety shells, no less than forty-seven are unknown
elsewhere--a wonderful fact, considering how widely distributed
sea-shells generally are. Of the forty-three shells found in other
parts of the world, twenty-five inhabit the western coast of
America, and of these eight are distinguishable as varieties; the
remaining eighteen (including one variety) were found by Mr. Cuming
in the Low Archipelago, and some of them also at the Philippines.
This fact of shells from islands in the central parts of the
Pacific occurring here, deserves notice, for not one single
sea-shell is known to be common to the islands of that ocean and to
the west coast of America. The space of open sea running north and
south off the west coast separates two quite distinct conchological
provinces; but at the Galapagos Archipelago we have a
halting-place, where many new forms have been created, and whither
these two great conchological provinces have each sent several
colonists. The American province has also sent here representative
species; for there is a Galapageian species of Monoceros, a genus
only found on the west coast of America; and there are Galapageian
species of Fissurella and Cancellaria, genera common on the west
coast, but not found (as I am informed by Mr. Cuming) in the
central islands of the Pacific. On the other hand, there are
Galapageian species of Oniscia and Stylifer, genera common to the
West Indies and to the Chinese and Indian seas, but not found
either on the west coast of America or in the central Pacific. I
may here add, that after the comparison by Messrs. Cuming and Hinds
of about 2000 shells from the eastern and western coasts of
America, only one single shell was found in common, namely, the
Purpura patula, which inhabits the West Indies, the coast of
Panama, and the Galapagos. We have, therefore, in this quarter of
the world, three great conchological sea-provinces, quite distinct,
though surprisingly near each other, being separated by long north
and south spaces either of land or of open sea.
I took great pains in collecting the insects, but excepting Tierra
del Fuego, I never saw in this respect so poor a country. Even in
the upper and damp region I procured very few, excepting some
minute Diptera and Hymenoptera, mostly of common mundane forms. As
before remarked, the insects, for a tropical region, are of very
small size and dull colours. Of beetles I collected twenty-five
species (excluding a Dermestes and Corynetes imported wherever a
ship touches); of these, two belong to the Harpalidae, two to the
Hydrophilidae, nine to three families of the Heteromera, and the
remaining twelve to as many different families. This circumstance
of insects (and I may add plants), where few in number, belonging
to many different families, is, I believe, very general. Mr.
Waterhouse, who has published an account of the insects of this
archipelago, and to whom I am indebted for the above details,
informs me that there are several new genera; and that of the
genera not new, one or two are American, and the rest of mundane
distribution. (17/4. "Annals and Magazine of Natural History"
volume 16 page 19.) With the exception of a wood-feeding Apate, and
of one or probably two water-beetles from the American continent,
all the species appear to be new.
The botany of this group is fully as interesting as the zoology.
Dr. J. Hooker will soon publish in the "Linnean Transactions" a
full account of the Flora, and I am much indebted to him for the
following details. Of flowering plants there are, as far as at
present is known, 185 species, and 40 cryptogamic species, making
together 225; of this number I was fortunate enough to bring home
193. Of the flowering plants, 100 are new species, and are probably
confined to this archipelago. Dr. Hooker conceives that, of the
plants not so confined, at least 10 species found near the
cultivated ground at Charles Island have been imported. It is, I
think, surprising that more American species have not been
introduced naturally, considering that the distance is only between
500 and 600 miles from the continent, and that (according to
Collnet, page 58) drift-wood, bamboos, canes, and the nuts of a
palm, are often washed on the south-eastern shores. The proportion
of 100 flowering plants out of 185 (or 175 excluding the imported
weeds) being new, is sufficient, I conceive, to make the Galapagos
Archipelago a distinct botanical province; but this Flora is not
nearly so peculiar as that of St. Helena, nor, as I am informed by
Dr. Hooker, of Juan Fernandez. The peculiarity of the Galapageian
Flora is best shown in certain families;--thus there are 21 species
of Compositae, of which 20 are peculiar to this archipelago; these
belong to twelve genera, and of these genera no less than ten are
confined to the archipelago! Dr. Hooker informs me that the Flora
has an undoubted Western American character; nor can he detect in
it any affinity with that of the Pacific. If, therefore, we except
the eighteen marine, the one fresh-water, and one land-shell, which
have apparently come here as colonists from the central islands of
the Pacific, and likewise the one distinct Pacific species of the
Galapageian group of finches, we see that this archipelago, though
standing in the Pacific Ocean, is zoologically part of America.
If this character were owing merely to immigrants from America,
there would be little remarkable in it; but we see that a vast
majority of all the land animals, and that more than half of the
flowering plants, are aboriginal productions. It was most striking
to be surrounded by new birds, new reptiles, new shells, new
insects, new plants, and yet by innumerable trifling details of
structure, and even by the tones of voice and plumage of the birds,
to have the temperate plains of Patagonia, or the hot dry deserts
of Northern Chile, vividly brought before my eyes. Why, on these
small points of land, which within a late geological period must
have been covered by the ocean, which are formed of basaltic lava,
and therefore differ in geological character from the American
continent, and which are placed under a peculiar climate,--why were
their aboriginal inhabitants, associated, I may add, in different
proportions both in kind and number from those on the continent,
and therefore acting on each other in a different manner--why were
they created on American types of organisation? It is probable that
the islands of the Cape de Verd group resemble, in all their
physical conditions, far more closely the Galapagos Islands than
these latter physically resemble the coast of America, yet the
aboriginal inhabitants of the two groups are totally unlike; those
of the Cape de Verd Islands bearing the impress of Africa, as the
inhabitants of the Galapagos Archipelago are stamped with that of
America.
I have not as yet noticed by far the most remarkable feature in the
natural history of this archipelago; it is, that the different
islands to a considerable extent are inhabited by a different set
of beings. My attention was first called to this fact by the
Vice-Governor, Mr. Lawson, declaring that the tortoises differed
from the different islands, and that he could with certainty tell
from which island any one was brought. I did not for some time pay
sufficient attention to this statement, and I had already partially
mingled together the collections from two of the islands. I never
dreamed that islands, about 50 or 60 miles apart, and most of them
in sight of each other, formed of precisely the same rocks, placed
under a quite similar climate, rising to a nearly equal height,
would have been differently tenanted; but we shall soon see that
this is the case. It is the fate of most voyagers, no sooner to
discover what is most interesting in any locality, than they are
hurried from it; but I ought, perhaps, to be thankful that I
obtained sufficient materials to establish this most remarkable
fact in the distribution of organic beings.
The inhabitants, as I have said, state that they can distinguish
the tortoises from the different islands; and that they differ not
only in size, but in other characters. Captain Porter has described
those from Charles and from the nearest island to it, namely, Hood
Island, as having their shells in front thick and turned up like a
Spanish saddle, whilst the tortoises from James Island are rounder,
blacker, and have a better taste when cooked. (17/5. "Voyage in the
U.S. ship Essex" volume 1 page 215.) M. Bibron, moreover, informs
me that he has seen what he considers two distinct species of
tortoise from the Galapagos, but he does not know from which
islands. The specimens that I brought from three islands were young
ones: and probably owing to this cause neither Mr. Gray nor myself
could find in them any specific differences. I have remarked that
the marine Amblyrhynchus was larger at Albemarle Island than
elsewhere; and M. Bibron informs me that he has seen two distinct
aquatic species of this genus; so that the different islands
probably have their representative species or races of the
Amblyrhynchus, as well as of the tortoise. My attention was first
thoroughly aroused by comparing together the numerous specimens,
shot by myself and several other parties on board, of the
mocking-thrushes, when, to my astonishment, I discovered that all
those from Charles Island belonged to one species (Mimus
trifasciatus) all from Albemarle Island to M. parvulus; and all
from James and Chatham Islands (between which two other islands are
situated, as connecting links) belonged to M. melanotis. These two
latter species are closely allied, and would by some ornithologists
be considered as only well-marked races or varieties; but the Mimus
trifasciatus is very distinct. Unfortunately most of the specimens
of the finch tribe were mingled together; but I have strong reasons
to suspect that some of the species of the sub-group Geospiza are
confined to separate islands. If the different islands have their
representatives of Geospiza, it may help to explain the singularly
large number of the species of this sub-group in this one small
archipelago, and as a probable consequence of their numbers, the
perfectly graduated series in the size of their beaks. Two species
of the sub-group Cactornis, and two of the Camarhynchus, were
procured in the archipelago; and of the numerous specimens of these
two sub-groups shot by four collectors at James Island, all were
found to belong to one species of each; whereas the numerous
specimens shot either on Chatham or Charles Island (for the two
sets were mingled together) all belonged to the two other species:
hence we may feel almost sure that these islands possess their
representative species of these two sub-groups. In land-shells this
law of distribution does not appear to hold good. In my very small
collection of insects, Mr. Waterhouse remarks that of those which
were ticketed with their locality, not one was common to any two of
the islands.
TABLE 17/1.
Column 1 : Name of Island.
Column 2 : Total Number of species.
Column 3 : Number of species found in other parts of the world.
Column 4 : Number of Species confined to the Galapagos
Archipelago.
Column 5 : Number confined to the one island.
Column 6 : Number of Species confined to the Galapagos
Archipelago, but found on more than the one island.
James : 71 : 33 : 38 : 30 : 8.
Albemarle : 46 : 18 : 26 : 22 : 4.
Chatham : 32 : 16 : 16 : 12 : 4.
Charles : 68 : 39* : 29 : 21 : 8.
*(or 29, if the probably imported plants be
subtracted.)
If we now turn to the Flora, we shall find the aboriginal plants of
the different islands wonderfully different. I give all the
following results (Table 17/1) on the high authority of my friend
Dr. J. Hooker. I may premise that I indiscriminately collected
everything in flower on the different islands, and fortunately kept
my collections separate. Too much confidence, however, must not be
placed in the proportional results, as the small collections
brought home by some other naturalists though in some respects
confirming the results, plainly show that much remains to be done
in the botany of this group: the Leguminosae, moreover, have as yet
been only approximately worked out:--
Hence we have the truly wonderful fact, that in James Island, of
the thirty-eight Galapageian plants, or those found in no other
part of the world, thirty are exclusively confined to this one
island; and in Albemarle Island, of the twenty-six aboriginal
Galapageian plants, twenty-two are confined to this one island,
that is, only four are at present known to grow in the other
islands of the archipelago; and so on, as shown in the above table,
with the plants from Chatham and Charles Islands. This fact will,
perhaps, be rendered even more striking, by giving a few
illustrations:--thus, Scalesia, a remarkable arborescent genus of
the Compositae, is confined to the archipelago: it has six species:
one from Chatham, one from Albemarle, one from Charles Island, two
from James Island, and the sixth from one of the three latter
islands, but it is not known from which: not one of these six
species grows on any two islands. Again, Euphorbia, a mundane or
widely distributed genus, has here eight species, of which seven
are confined to the archipelago, and not one found on any two
islands: Acalypha and Borreria, both mundane genera, have
respectively six and seven species, none of which have the same
species on two islands, with the exception of one Borreria, which
does occur on two islands. The species of the Compositae are
particularly local; and Dr. Hooker has furnished me with several
other most striking illustrations of the difference of the species
on the different islands. He remarks that this law of distribution
holds good both with those genera confined to the archipelago, and
those distributed in other quarters of the world: in like manner we
have seen that the different islands have their proper species of
the mundane genus of tortoise, and of the widely distributed
American genus of the mocking-thrush, as well as of two of the
Galapageian sub-groups of finches, and almost certainly of the
Galapageian genus Amblyrhynchus.
The distribution of the tenants of this archipelago would not be
nearly so wonderful, if, for instance, one island had a
mocking-thrush, and a second island some other quite distinct
genus;--if one island had its genus of lizard, and a second island
another distinct genus, or none whatever;--or if the different
islands were inhabited, not by representative species of the same
genera of plants, but by totally different genera, as does to a
certain extent hold good; for, to give one instance, a large
berry-bearing tree at James Island has no representative species in
Charles Island. But it is the circumstance that several of the
islands possess their own species of the tortoise, mocking-thrush,
finches, and numerous plants, these species having the same general
habits, occupying analogous situations, and obviously filling the
same place in the natural economy of this archipelago, that strikes
me with wonder. It may be suspected that some of these
representative species, at least in the case of the tortoise and of
some of the birds, may hereafter prove to be only well-marked
races; but this would be of equally great interest to the
philosophical naturalist. I have said that most of the islands are
in sight of each other: I may specify that Charles Island is fifty
miles from the nearest part of Chatham Island, and thirty-three
miles from the nearest part of Albemarle Island. Chatham Island is
sixty miles from the nearest part of James Island, but there are
two intermediate islands between them which were not visited by me.
James Island is only ten miles from the nearest part of Albemarle
Island, but the two points where the collections were made are
thirty-two miles apart. I must repeat, that neither the nature of
the soil, nor height of the land, nor the climate, nor the general
character of the associated beings, and therefore their action one
on another, can differ much in the different islands. If there be
any sensible difference in their climates, it must be between the
windward group (namely, Charles and Chatham Islands), and that to
leeward; but there seems to be no corresponding difference in the
productions of these two halves of the archipelago.
The only light which I can throw on this remarkable difference in
the inhabitants of the different islands is that very strong
currents of the sea running in a westerly and west-north-westerly
direction must separate, as far as transportal by the sea is
concerned, the southern islands from the northern ones; and between
these northern islands a strong north-west current was observed,
which must effectually separate James and Albemarle Islands. As the
archipelago is free to a most remarkable degree from gales of wind,
neither the birds, insects, nor lighter seeds, would be blown from
island to island. And lastly, the profound depth of the ocean
between the islands, and their apparently recent (in a geological
sense) volcanic origin, render it highly unlikely that they were
ever united; and this, probably, is a far more important
consideration than any other with respect to the geographical
distribution of their inhabitants. Reviewing the facts here given,
one is astonished at the amount of creative force, if such an
expression may be used, displayed on these small, barren, and rocky
islands; and still more so, at its dive
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