The Solomon Islands and Their Natives Part 41

BATRACHIANS.--The Spanish discoverers in 1567 remarked that the natives of Isabel worshipped the toad (_vide_ page 203), and one of the officers of Surville's expedition in 1769, described in his journal a remarkable toad from the same island;[446] yet it is only within recent years that any Batrachians have been collected in this region. Before I arrived in the group only two species were known to science, and to this number my collections, which were made in the islands of Bougainville Straits, have added seven new species, including a type of a new family. The following list represents the Batrachian fauna of the Solomon Islands, as far as it is at present known:

[446] "Discoveries of the French in 1768 and 1769," &c., by M.

Fleurieu: London, 1791; p. 134.

_Ranidae._

Rana buboniformis, _n. sp._ Rana guppyi, _n. sp._ Rana opisthodon, _n. sp._ Rana krefftii.

Cornufer guppyi, _n. sp._ Cornufer solomonis, _n. sp._

_Ceratobatrachidae._

(New family characterised by both jaws being toothed, and by the diapophyses of the sacral vertebra not being dilated.) Ceratobatrachus guentheri, _n. sp._

_Hylidae_ (Tree-frogs.)

Hyla macrops, _n. sp._ Hyla thesaurensis.

The natives of the islands of Bougainville Straits, where, as I have just remarked, my batrachian collection was chiefly made, have given frogs the general name of "appa-appa" in imitation of their noise, just as they have named the smaller lizards "Kurru-rupu" for the same reason.

Amongst the particular species of frogs, I may refer to the large toad-like _Rana buboniformis_, which I found in Treasury Island, and on the highest peak of the island of Faro. _Rana guppyi_, according to Mr.

Boulenger's report, attains a larger size than any other species of the genus, with the exception of the Bull-Frog of North America. _Rana opisthodon_ affords an instance of a Batrachian[447] which dispenses with the usual larval or tadpole stage, "the metamorphoses being hurried through within the egg." On this subject I made the following notes.

Whilst descending from one of the peaks of Faro Island, I stopped at a stream some 400 feet above the sea, where my native boys collected from the moist crevices of the rocks close to the water a number of transparent gelatinous b.a.l.l.s rather smaller than a marble.[448] Each of these b.a.l.l.s contained a young frog about 4 lines in length, apparently fully developed, with very long hind legs and short fore legs, no tail, and bearing on the sides of the body small tufts of what seemed to be branchiae. On my rupturing the ball or egg in which the little animal was doubled up, the tiny frog took a marvellous leap into its existence and disappeared before I could catch it. When I reached the ship an hour after, I found that some of the eggs which had been carried in a tin had been ruptured on the way by the jolting, and the liberated frogs were leaping about with great activity. On placing some of them in an open bottle 8 inches high, I had to put the cover on as they kept leaping out. Mr. Boulenger remarking on this observation says, that there are no gills, but that on each side of the abdomen there are regular transverse folds (with an arrangement like that of the gill-openings of Plagiostomous Fishes), the function of which probably is that of breathing-organs. The tip of the snout is, he says, furnished with a small conical protuberance, projecting slightly through the delicate envelope of the egg, and evidently used to perforate that covering. In the instance also of _Cornufer solomonis_, another new species included in my collection, Mr. Boulenger remarks that there is every reason to believe that the young undergo the metamorphoses within the egg.

[447] Hylodes martinicensis affords another instance. Mon. Berl.

Ac., 1876, p. 714.

[448] According to Mr. Boulenger, they measure from 6 to 10 mm. in diameter.

With regard to the interesting species, _Ceratobatrachus guentheri_, which forms the type of a new family, _Ceratobatrachidae_, the same writer observes that it is remarkable for the numerous appendages and symmetrical folds which ornate its skin. It is, in fact, "all points and angles," and may be truly termed a horned frog. There is great variation both in the coloration and in the integuments. "Out of the twenty specimens before me," thus Mr. Boulenger writes, "no two are perfectly alike." The development is presumed to be of the type in which the metamorphoses are hurried through within the egg. These horned frogs are very numerous in the islands of Bougainville Straits, and so closely do they imitate their surroundings, both in colour and pattern, that on one occasion I captured a specimen by accidentally placing my hand upon it when clasping a tree.

It is particularly important to notice not only that the Batrachians of the Solomon Islands, as far as we at present know, do not occur elsewhere, but also that in this region a distinct family has been produced. These facts support the conclusions deducible from the geological evidence that these islands are of considerable geological age (_vide_ page x.). The insular and isolated conditions have been preserved during a period sufficiently extended for the development of a peculiar Batrachian fauna.

The modes of dispersal of frogs and toads, and, in truth, of the whole Batrachian cla.s.s, are matters of which we are to a great extent ignorant. Frogs are usually stated to be absent from oceanic islands, a peculiarity of distribution which apparently accords with the circ.u.mstance that neither they nor their sp.a.w.n can sustain submersion in sea-water. The occurrence, however, of three species of _Cornufer_ in the Caroline and Fiji Islands, and of a species of _Bato_ in the Sandwich Islands,[449] affects the general application of this conclusion. It may be suggested that these exceptions are due to human agency; but if so, it is difficult to understand why they have not been found in such a well explored island as New Caledonia.[450]

[449] Boulenger's "Catalogue of the Batrachia Gradientia," &c., 2nd edit., 1882.

[450] Perhaps the peculiar geographical distribution of the Batrachia may throw light on this subject. _Ibid._

In concluding this chapter I will refer to the circ.u.mstance that my collections of the Reptiles and Batrachians of this large group have only in a manner broken ground in a region which promises the richest results to the collector. It cannot be doubted that in the elevated interiors of the large islands, such as those of Bougainville and Guadalcanar, there will be found a peculiar Reptilian and Batrachian fauna, the study of which will be of the highest importance for the furtherance of our knowledge of these geologically ancient cla.s.ses of animals. I believe I am correct in stating that it was on account of the highly interesting Batrachian collections I sent to the British Museum, that I received a grant for further exploration from the Royal Society, which, however, I was unfortunately prevented from turning to account.

The work has yet to be done, and there can be little doubt that the man who is first able to examine the lofty interior of such an island as Guadalcanar will bring back collections, the importance of which will amply recompense him for any hardship or personal risk he may have endured. My experience was confined to the sea-border and its vicinity.

The future explorer will find his field in the mountainous interiors and on the highest peaks.

NOTE (April 19th, 1887).--Since I penned the above, further collections of reptiles and batrachians, made in these islands by Mr. C. M. Woodford, have been described by Mr. Boulenger at a recent meeting of the Zoological Society. I had the pleasure of meeting Mr.

Woodford before he left England, and I hope that he has been able to accomplish his purpose of penetrating into the interior of one of the larger islands of the group.

CHAPTER XV.

GENERAL NATURAL HISTORY NOTES.

AMONGST the numerous strange acquaintances which I made in the Solomon Islands, was that of the well known cocoa-nut crab, or _Birgus latro_; and I take this opportunity of giving my evidence towards the establishment of the fact of its cocoa-nut-eating propensity, for the following reason. When I read my notes on the subject before the Linnean Society of New South Wales on Dec. 27th, 1882,[451] I was surprised at the incredulity shown with reference to this extraordinary habit; and on inquiry, I learned that the evidence on the subject was deficient in one vital point, viz., the production of the writer who had witnessed this habit of the Robber Crab. Accordingly I referred to the various authors who have recorded this habit of the _Birgus_, and in no single account could I find that the writer had witnessed what he described. Neither Mr. Darwin, Dr. Seemann, Messrs. Tyerman and Bennet, Mr. T. H. Hood, the Rev. Wyatt Gill, nor the numerous authors whose accounts I also examined, seem to have actually witnessed the _Birgus_ opening and eating a cocoa-nut. Herbst[452] was among the first to refer to this habit; whilst, long ago, M. M. Quoy and Gaimard[453] a.s.serted, from their own observation, that the crab was fond of cocoa-nuts, and could be supported on them alone for many months, but they made no allusion to its capability of husking and opening them. The evidence on this point appears to have been always tendered by natives, excepting the account given to Mr. Darwin by Mr. Liesk, which is conclusive in itself.[454]

Yet, credulous persons had fair grounds to retain their doubts, although in various works on natural history, popular and otherwise, this habit of the _Birgus_ was described as an undoubted fact. I therefore submit my evidence; leaving to my reader to reply to the query--Can there be any reasonable doubt on the subject?

[451] Proc. Lin. Soc. N.S.W.

[452] Proc. Zool. Soc, 1832, p. 17.

[453] Freycinet's "Voyage autour du Monde," 1817-20: Zoologie, p.

536. (Paris, 1824.)

[454] "Journal of Researches," p. 462.

The _Birgus_ was to be found in most of the islands we visited. It is to be usually observed at or near the coast; but on one occasion, in St.

Christoval, I found an individual at a height of 300 feet above the sea.

Whilst traversing, in September, 1882, the belt of screw-pines, which borders the beach on the east coast of Malaupaina, the southern island of the Three Sisters, I came upon one of these large crabs, ensconced in the angle between the b.u.t.tressed roots of a tree, with a full sized cocoa-nut within the reach of its pair of big claws. From the fresh-looking appearance of the sh.e.l.l, it had been evidently, but recently, husked, which operation had been performed more cleanly than if a native had done it. There was an opening at the eye-hole end of the sh.e.l.l of a somewhat regular oblong form, which measured 2 by 1 inches, and was large enough to admit the powerful claws of the crab.[455] The white kernel, which had the firm consistence of that of the mature nut, had been scooped out to the extent of from 1 to 1 inches around the aperture; small pieces of the kernel lay on the ground outside the nut, and others were floating about in the milk inside, of which the sh.e.l.l was about a fourth-part full.

[455] This sh.e.l.l was presented to the Australian Museum, Sydney.

I had, without a doubt, disturbed the _Birgus_ in the middle of its meal; but, curiously enough, there were no cocoa-nut palms to be seen within fifty paces of the spot where the crab was found in its retreat.

Not only had the sh.e.l.l been very recently husked, but it was evident, from the fresh condition of the milk and kernel, that an interval of less than a couple of hours had elapsed since the opening had been made.

There was no possible explanation of the crab having got at the edible portion of the cocoa-nut, except through its own agency. The island is uninhabited, being only occasionally visited by fishing-parties of natives from St. Christoval, none of whom were on the island during the ship's stay. There was, therefore, the strongest presumptive evidence that the _Birgus_ had not only husked the cocoa-nut, but had also broken the hole at the end, in order to get at the kernel.

I kept the crab alive on board on a diet of cocoa-nuts for three weeks, when, one morning, to my great disappointment, I found it dead. Other foods, such as bananas, were offered to it but were left untouched, and its appet.i.te for cocoa-nuts continued unimpaired to the last day of its life. Being desirous of observing the manner in which the husk was removed, I had a cocoa-nut with its husk placed in the coop in which the crab was kept. On one occasion the _Birgus_ was surprised with the nut between its large claws; but, notwithstanding that no other food was offered to it for a day and a half, it did not attempt to strip off the husk. So the operation was done for it, and a small hole was knocked in the top of the sh.e.l.l. On the following day I found the sh.e.l.l--a young and somewhat thin one--broken irregularly across the middle, with the soft white kernel already removed and eaten. It was afterwards found necessary to break the nuts for its daily food.

In 1884, when the "Lark" was in Bougainville Straits, three of these crabs were kept on board with the intention of taking them down to Sydney. Mr. W. Isabell, leading-stoker of the ship, looked well after them, as he had also done in the case of the previous crab, but within three or four weeks they had all died. The cocoa-nuts had to be husked and broken for them, as they were in vain tempted to do it for themselves. One crab, however, was frequently observed clasping between its claws a full-grown unhusked nut, the upper end of which showed deep grooves and dents from the blows of its claws; and Mr. Isabell and I came to the conclusion that the coop, in which these crabs were placed, was too low to allow of the free play of the great claws.

My evidence alone would be sufficient to convict the _Birgus_ of this offence: for an offender it would certainly be in the eyes of the owner of a plantation of cocoa-nut palms. I learned from Mr. Isabell that the first crab we had on board consumed, on the average, two cocoa-nuts in three days. A number of these crabs in a cocoa-nut plantation, might therefore prove a considerable pest: for, if this betokens the quant.i.ty of food which the _Birgus_ consumes in a state of nature, a single crab in the course of twelve months would dispose of about 250 cocoa-nuts, which represent the annual production of three palms and between 20 and 30 quarts of oil.

As these crabs disliked observation, I was unable to gain much knowledge of their habits by watching. During the day-time they were sluggish, did not eat, and kept themselves in the further corner of the coop, as far from the light as possible. At night they moved about very actively and fed vigorously on the cocoa-nuts. The natives of the Shortlands, who were well-acquainted with the cocoa-nut eating habit of the _Birgus_, described to me the mode of husking and breaking the nut, just as Mr.

Liesk described it to Mr. Darwin. They esteem as an especial luxury the fat which gives the chief bulk to the abdomen of the crab.

The habit of the _Birgus_, when surprised away from its burrow, is not to turn round and run away, but to retreat in an orderly manner with its front to the foe. Having reached some root or trunk of a tree which protects in the rear its less perfectly armoured abdomen, it makes a regular stand, waves one of the long second pair of claws in the air, and courageously awaits the attack. The att.i.tude of defence is worthy of remark. The two large claws are held up close together to defend the mouth and eyes, but with the pincers pointing downward--the posture reminding me of the guard for the head and face in sword-exercise. One of the long second pair of claws is planted firmly on the ground to give the crab additional support; whilst the other claw is raised in the air and moved up and down in a sparring fashion. The whole att.i.tude of the _Birgus_, when on the defensive, is one of dogged and determined resistance. The big pincers that point downward are ready to seize anything which touches the unprotected under surface of the abdomen; but on account of the position of these claws in front of the eyes, it can only foresee attacks from above, and it therefore cannot ward off a sudden thrust directed against the abdomen, although it may afterwards inflict severe injuries on the aggressor.

There seems to be some doubt whether the _Birgus_ ascends the tree to get the cocoa-nuts or whether it contents itself with those that have fallen. Almost every author who refers to this crab alludes to its climbing the tree, and it is also said to climb the panda.n.u.s. The testimony in support of its climbing powers is almost conclusive, yet Mr. Darwin was informed by Mr. Liesk that in Keeling Atoll the _Birgus_ lives only on the fallen cocoa-nuts, and Mr. H. O. Forbes,[456] who has recently visited this island, confirms this statement.

[456] "A Naturalist's Wanderings," etc.: London, 1885, p. 27.

My readers, after perusing the foregoing remarks, will agree with me that from the lack of actual observation on the part of the authors, who describe the cocoa-nut eating habit of this crab, there has been fair grounds for scepticism. Even now, we are but imperfectly acquainted with the mode of life of the _Birgus_, which is a subject I would commend to the attention of residents in the Indian and Pacific Oceans.

I may add that the _Birgus_ is partial to other kinds of fruits beside cocoa-nuts. Different writers mention candle-nuts, nutmegs, figs, and other rich and oily nuts and fruits. In some islands it would seem that the Panda.n.u.s fruit is its only diet; and for breaking open these tough fruits, its heavy claws are well adapted, though from personal experience, I should remark that the crab would have its strength and ingenuity taxed almost as much as in the case of the cocoa-nut.

[Ill.u.s.tration]