Recent Occurrence of Pelamis platurus Linn. in New Zealand.
[Read before the Wellington Branch, October 23, 1940; received by the Editor, October 30, 1940; issued separately, June, 1941.]
On Thursday, 19th May, 1938, at the northern extremity of Mahia Peninsula, near Table Cape, two children noticed a sea-snake some little distance from the sea. The reptile was captured by Mr. Teihi Peka, who succeeded in throwing a loop over its head. Realizing the importance of their find, the Maoris forwarded the sea-snake to the Editor, Wairoa Star, who placed the specimen in methylated spirit and presented it to this Museum. The snake was readily identified with the common Pacific or yellow-bellied sea-snake. Pelamis platurus Linn., a highly-venomous species with a striking colouration. The lower surface is bright yellow and the back is brown or black. So characteristic of this species is this colour that Kinghorn (1929) states that this is sufficient for its identification.
There are, however, a number of interesting features of the Mahia specimen which are worthy of record here. The thickest part of the body is at a point posterior to midway between point of snout and tip of tail, the diameter of the body at this point being less than twice that of the neck. The body scales are hexagonal or quadrangular in shape, the lowermost rows with two or three small turbercles. Malcolm Smith (1926) notes that these are strongest in adult males. Ventral scales are divided below by a median longitudinal line. The nostrils are superior, nasal shields being in contact with each other. A more or less definite neck is present, surrounded by 49 series of scales arranged in longitudinal rows, 21 being dorsal (black) and 28 being ventral (yellow). Across the widest portion of the head there are dorsally 17 scales, all being on the black area, those in the centre very much larger. Scales round the widest portion of the body number 26–27 dorsal (black) and 30–31 ventral (yellow). There are some 330 scales along the ventral surface, and, in addition, tail scales are approximately 46 in a longitudinal series. Most teeth are broken, ten in lower jaw, together with two stumps, being counted. Poison fangs are broken. The total length is 29·3 in. Of this length the tail is 4·1 in.
Mr. W. W. Smith, New Plymouth, reports that during the long, extremely dry and hot summer of 1933 five examples of this sea snake were taken on the Taranaki coast. In April, 1938, a brightly-coloured specimen was captured on the lawn at the East End Reserve, New Plymouth, three chains from the sea. Through the courtesy of Mr. W. W. Smith and Mr. W. H. Skinner, Curator of the New Plymouth Museum, this example was presented to the Dominion Museum. A light covering of fungus appears on parts of the body and extends into the mouth, the teeth being more or less embedded in it.
Compared with the Mahia example, we find the teeth are relatively smaller. Ten teeth may be counted on one side in the lower jaw and 12 on the other. On one side of the upper jaw there are six teeth behind the poison fang. Some 14 palatine teeth may be counted to the angle of the jaw. Scales are in 37 rows around the neck, 19 dorsal (black) and 28 ventral (yellow). Around the widest part of the body they are in 56 series, 17 dorsal (black) and 39 ventral (yellow). The scales across the head are partly destroyed; but those along the ventral surface number 330. The tail scales are 43 in a longitudinal series. The total length is 24·6 in.
This snake from New Plymouth had an even more vivid colouration than that of the specimen from Mahia. The mottled markings on the tail and lips were particularly well-defined. Apparently, it had been killed by a blow on the head, but was biting its own body viciously in death, and had been preserved in that attitude. The specimen was at first deposited in the New Plymouth Museum; but that Institution already had five others captured during the above-mentioned long period of dry summer weather on the Taranaki coast. From this it will be seen that during any particularly warm period there always is the possibility of a southern migration of these snakes taking place. Those cast ashore may be a few out of large numbers.
Malcolm Smith (5, p. 118) classifies Pelamis platurus into seven colour divisions according to the relative positions of brown, yellow and black on the body surface. Both our examples fit into his first division, which is: Black above, yellow or brown below, the two colours being sharply defined; head black above, the upper lip usually yellow. Widely distributed. Division 4 appears closely related, but differs in the addition of a lateral series of black spots which may be confluent into a stripe.
Cheeseman (3, p. 268) records 9 examples as having been found in New Zealand between 1868 and 1907, while there are occasional references in the daily papers to others that have come ashore since that time.
Malcolm Smith (loc. cit., p. 120) records two examples in the British Museum taken in New Zealand waters, both being females, one belonging to his first colour group has 60 scales round the body and 406 along the ventral, while the other, belonging to colour group 4, has 62 scales around the body and 338 on the ventral surface.
Bibliography to Literature Consulted.
1. Krefft, Gerard, 1809. The Snakes of Australia, p. 98.
2. Cheeseman, T. F., 1888. Trans. N.Z. Inst., vol. 20, p. 165.
3. T. F. Cheeseman, 1908. Trans. N.Z. Inst., vol. 40, p. 268.
4. Oliver. W. R. B., 1911. Reptiles and Mammals of the Kermadec Islands, Trans. N.Z. Inst., vol. 43, p. 536.
5. Smith, Malcolm, 1929. Monograph of the Sea Snakes (Hydrophiidae). British Museum, London.
6. Kinghorn. J. R., 1929. Snakes of Australia (with numerous coloured figs.), p. 118.