MAWSON EXPEDITION

Taranaki Daily News, 1 August 1930, Page 7

MAWSON EXPEDITION

FOOD OF SEA ANIMALS ANTARCTIC BIRD LIFE. PENGUINS’ DOMESTIC WAYS. (By Sir Douglas Mawson. — All Rights Reserved.) No. VI. The chief biologist to the expedition, Professor T. Harvey Johnston, in the course of his report on the work writes: — It is from the plankton that the majority of animals in the sea ultimately derive their supply of food — hence the importance of its study. It consists largely of microscopic plants called diatoms, and of small crustaceans, together with pelagic molluscs (pteropods), various kinds of worms and jellyfish, the larvae of fish and invertebrates, and lowly animals belonging' to the protozoa, such as radiolaria and foraminifera. As many of these organisms have skeletons of silica or of lime, there becomes built up on the ocean floor, as a result of the death of these small creatures, an ooze, classified according to its main constituent and varying according to depth and locality. Diatom ooze predominates on the Antarctic sea floor, the diatoms occurring in enormous numbers in the more superficial portions of Antarctic and sub-Antarctic waters, imparting.to them a peculiar greenish appearance markedly different from the deep, blue colour of the water of similar depth; but containing relatively few of these siliceous plants. As this sufacc layer becomes frozen, it is usual to find.' a broad yellowish or greenish band in the packice, the colour being due to these included diatoms. ...... SOURCE OF FOOD SUPPLY. Since diatoms are able to build up living material from inorganic matter in the ocean, and to store up energy derived from the sun’s rays, they, together with other microscopic pelagic plants (phytoplankton), form the great source of 'food supply from which animal life derives its nourishment, directly or indirectly. Hence abundance' of phytoplankton is correlated with-abundance of planktonic animal life ranging from microscopic species to those measuring an inch or more in length, e.g., kril. Of. ecurse there are much larger organisms in the plankton—such as medusae, certain worms, etc., but they probably play a minor role as sources of food supply for other organisms. In order to collect organisms from deeper waters dredging was resorted to, various kinds of dredges being utilised according to the depth. In some cases a heavy Monagasque trawl was used while in others another trawl was employed. The latter was expected to take fish chiefly, and though it was not very successful for that purpose, it proved an excellent means for obtaining many kinds of invertebrates in good condition from the sea floor; The life on the latter is very abundant, ’ but dredging in Antarctic waters present difficulties on account of the abundance of rocks of various sizes dropped by-icebergs during their drift from Antarctic lands to warmer regions. These commonly tear the net or even break the heavy steel frame of the dredge. Then there .are also difficulties associated with heavy weather, a rolling ship and a cold climate, which should render especially valuable any material brought back from the great depths or from' the Antarctic continental shelf.. A fine collection of specimens has been obtained as a result of this work, and will be distributed later on to specialists in yari-c-is parts of the world for investigation and report. FOOD GF VERTEBRATES.

Throughout the cruise, when tinie permitted, an examination of the various vertebrates collected —fish, birds and mammals —was made with a view to'ascertaining (he nature of their'food. The fish were found to feed on other fish, worms or crustacea. The albatross and the majority of petrels utilised cuttlefish of various species, and the remainder' fed on crustaceans. Some penguins fed on fish and others on crustaceans, such as kril (whole food). Other birds captured insects or organisms living between tidemarks, while some were scavengers, and others were fisheaters. • i

The ornithologist to- the--expedition, Mr. R. A. Falla, submitted a report on bird life, extracts from which are as follows: —

Bird life in the Antarctic regions and in the great Southern Ocean that Iks around them has been a source of interest to every member of the. expedition. The scientific work has included a study of bird distribution at sea, nest-, ing habits on wind-swept- islands and ice-bound coasts, _ with special attention to such little known areas as Heard Island and the coasts of the mew land in. Antarctica. Only a few..of the more interesting observations can be mentioned, as the full details are reserved for, a scientific report which will be based upon a further study of our extensive collection of specimens. ’ WAYS OF OCEANIC BIRDS. If the track of the Discovery is traced it will be seen that a. considerable area of the Southern Ocean was traversed. Including, the voyage of the Australian members of the scientific staff to Capetown, we completed, between September,. 1929, and April, 1930,'a great figure-of-eight course of more, than 15,000 'miles with Kerguelen as ite centre. There was not one day. upon which some. birds were not seen, and as far as possible a record was kept of the species . that could be recognised, the approximate numbers and the- direction of any definite migratory movement.. The results show that even oceanic birds do not wander indiscriminately about the seven seas. Their range at any season is determined by the position of suitable islands for breeding arjl th seasonal movements of the surface plankton on which they feed. A week out. of Capetown, in ‘latitude 40deg. south, we met with vast flocks of the birds known to old whalers as “whalebirds,” because of their habit of foliowi”g whales about. Several times during that day the dark backs of fin-whales broke surface near the ship, and at once myriads of birds were hovering over the swirling water to pick up marine organisms thus disturbed. • A short stay was made at Possession 1,-land, Crozet Group, and shore work confined to a few hours in American Bay. Penguins here were represented by*a well-built and vigorous race of the Gentoo or “Johnny”. penguin, and a fpw of the smaller crested rockhoppors which

1 .d not begun nesting. With Gentoos, nesting must begin very early in the season, for well-grown young birds were standing about in nursery groups attended by a few old birds on nurse duty. The majority of the adults were not seen until they returned from the sea in the evening distended with food for tha young. Toiling ’thus handicapped up the steep tussocky slopes to the rookery they are a picture of discomfort and domestic sacrifice, a solemn warning quite' ignored by other Gentoos, which are busy arranging new nests near by.