PAPERS AND PROCEEDINGS OF THE: ROYAL SOCIETY OF TASMANIA, VoLUME 93 PRELIMINARY NOTES ON NOTECHIS SCUTATUS NIGER KINGHORN, ON CAT ISLAND, FURNEAUX GROUP, TASMANIA

By

TERENCE CASHION Tasmanian lVluseurn, Hobart

ABSTRACT Snake, this variety is generally accepted as a The occurrence of Notechis scutatus niger on Cat melanistic form of the mainland species. The Island is recorded and its feeding habits and predominant colour is black, but several specimens comparisons with the common mainland species of olive-brown eolouration were met with which discussed. showed faint traces of transverse banding. Some authorities suggest that this insular form i.s lethar­ Details of examinations of fifteen specimens of gic as compared with the mainland species. I Notechis scutatus niger collected on the island are did not always find this so. On a number of given. occasions disturbed individuals made off into the INTRODUCTION tussocks or down burrows with an agility and The following observations are based on a stay speed very comparable with tiger snakes I have of some nine weeks on Cat Island between January observed on the Tasmanian mainland. 14th and March 18th, 1957. If Notechis scutatus niger does at times show a Cat Island is well known for its gannE't colony, tendency towards torpidity it could be influenced and my wife and I, on behalf of the Tasmanian by either one of two factors or a combination of Animals and Birds Protection Board, visited the both. An overindulgent food supply could induce island to protect the gannets during their breeding torpidity as could bleak weather conditions which period. often prevail in their island homes. The stay gave us good opportunity to observe and compile notes on other aspects of the island's Compared with the common tiger snalw, the fauna. island variety is also regarded as averaging greater The present paper is on the occurrence of Notechis size, individuals exceeding six feet in length having scutatus niger on Cat Island. (For an account of been recorded. This would indicate an abundant the bird life of the island see Cashion, The Emu_. food supply as it is certain size and rate of growth VoL 58, p. 327.) in snakes is influenced greatly by the amount of food available. On Cat Island it would seem there THE ISI,AND is a definite food cycle which would fluctuate, and, Cat Island Oat 39" 57' S,, long. 148' 21' E.) lies due to the availability of young birds, would reach three or four miles off the exposed east coast of its peak at or about the time of my visit. Flinders Island in Bass Strait. It is flanked by two closely adjacent islands; the much larger Babel It would make an interesting study to follow this Island off the west shore, and the slightly smaller food cycle as it would then be possible to obtain Storehouse Island off the south-east shore. a more complete picture of the diet of the snakes at the various stages of the cycle, but such an Cat Island, generally, is low lying, irregular in analysis would, of course, entail an examination shape, and is approximately a mile long and nearly of a large number of stomach contents. as broad at its widest point. The shoreline is almost entirely rocky, the east A cursory examination of stomach contents of shore particularly so. There are two small sandy Notechis scutatus niger on Cat Island would suggest beaches of about equal size, one on the south side a tendency for the larger individuals to feed of the island, and the other opposite on the north principally on the small young of the Short-tailed shore. The island is honeycombed with shear­ Shearwater (Pu[finns tenuirostris) when these were water and penguin burrows and for the main part available, whilst the smaller specimens would con­ is covered with tall dense tussocky grass (Poa). centrate more generally on small skink lizards Other plant species occur as well. A creeping (Leiolapisma) which are very plentiful on the native spinach

111 112 NOTES ON NOTE,CHIS SCUTATUS NIGER KINGHORN ON CAT ISLAND

It seems certain they are most active during 1.2.1957:- cooler conditions, especially before and after a Length: 1,000 millimetres. rainstorm. On one occasion under such circum­ Weight: 385 grams. stances five snakes were encountered within a few Colour: Olive-brown, faintly indicated tra­ minutes in a small area near the hut. Throughout verse bands yellowish-brown; under-­ hot spells their absence was most noticeable, part,c;, throat, pale-yellow, darkening apparently preferring the relative coolness of a towards tail. '? thirteen young (aver­ burrow or the shade of the dense tussocks. aging 150-160 millimetres in length l in bifurcate uterus. The young, brown­ The following notes are details of examinations ish-black in colour, were traversely of fifteen specimens of Notechis scutatus niger banded. collected on Cat Island. Stomach contents: Two legs of a very young Shearwater. 14.1.1957:- 1.2.1957:- Length: 785 millimetres. Length: 1,285 millimetre:;:. Weight: 90 grams. Weight: 575 grams. Colour: Dark-brown; faint traverse bands. Colour: Black; underparts dark-slate; (No other data recorded.\ throat yellowish-white. 6 '? 25.1.1957:-- Stomach contents: Partly digested remains Length: 847 millimetres. of a young Shearwater. Weight: 120 grams. 7.2.1957:- Colour: Blackish-brown. (No other data Length: 1,125 millimetres. recorded.) Weight: 420 grams. 28.1.1957:-- Colour: Brownish-olive, faintly banded Length: 720 millimetres _ yellowish-brown; underparts greenish­ Weight: 80 grams. slate darkening towards tail; throat Colour: Black. yellow. 6 testes not enlarged. Stomach contents: One small skink