1987/88 Field Season at Heard Island.
Harry R. Burton. Field Leader, Antarctic Division.
The 1987/88 ANARE to Heard Island was the last of a series of three summer programs there (1985 and 1986/87); and with five and a half months on the Island. It was also the longest. Earth science had been the primary focus of the 1986/87 program. In 1987/88 the focus of the work was again biology, as it had ... been in 1985; and island transport (other than pedestrian) was by LARC.
Nella Dan delivered the party of 17 from September 18 to 20 1987, with four at Spit Bay and the remainder at Atlas Cove. About a month later, on October 18 and 19 she returned: four of the party left and there were two new arrivals, so that 15 people were on the Island until Lady Franklin picked up the party and left on March 2 1988.
A major task of the Expedition was to carry out a complete census of Heard Island's breeding population of Southern Elephant Seals. This task was done in the middle of October, when the numbers of cows hauled out to pup on the beaches were at a maximum and counts made at that time were sensibly referable to other years and other islands. It was the first total census ever completed on Heard Island although one made in 1985 was nearly so. The party was able to walk to Long Beach and census that area. and the availab1l1ty of a helicopter for two days allowed the total photographic coverage of Spit Island, a sedimentary island little more than a metre above sea level and about a kilometre to the east. This island is home to several thousand seals. The one photographic run over this island on October 18 produced a 70mm film record. and thus the whole Island census was completed. Although strong winds during the photography prevented complete overlap of all the aerial photographs. allowance for the small proportion of missed ground was made in censusing. The final total for Spit Island was 3,200 plus or minus 150 cows.
A number of other whole Island Southern Elephant Seal counts (excluding Spit Island) were made at intervals of approximately a month so that seal numbers at particular sites and dates could be compared to historical records for these same places at equivalent seasonal times. These counts also gave quantitative measures of 'seal abuse' to coastal vegetation.
A daily count of all Southern Elephant Seals in the Four Bays area was maintained for two months. This work enabled the day of maximum numbers to be calculated with precision, as well as providing a detailed record of the haul-out pattern for comparison with other years and islands.
The day of maximum numbers, 17 October, was two days later in 1987 than in 1985. The results also indicated a further small reduction in the pup production of the Four Bays area, compared to 1985. However a complete enumeration of the seals on all island beaches still waits on a careful checking of all data.
Another Southern Elephant Seal study was the weighing of weaned pups. About 400 pups were weighed at each end of the Island. The total (821) is a considerable data set and it demonstrated the variation in sex ratio and weight through the weaning period. Male pups had a mean weight of 116.5kg (408 animals), and female pups had a mean weight of 111.6kg (413 animals). These data allow real comparison with weaned weights from other islands and thus may provide insights into the reasons for the decline of seal numbers on some islands (the Indian Ocean Sector) and not others (South Georgia). Sixty Southern Elephant Seals. newly arrived at the beach to moult, were anaesthetised, measured and weighed before having their stomach contents flushed out by water through a soft rubber hose. These collections contained obvious examples of squid beaks and stomach worms but await analysis. This will provide the first detailed information on the diet of these seals in the Heard Island area.
Leopard Seals were counted whenever they were seen, and at times (late February) they out numbered Southern Elephant Seals on some beaches. Thirty five animals were anaesthetised. measured and weighed before being tagged and their blood sampled.
A surprise was the discovery of two Subantarctic Fur Seals bearing tags from Marion Island. This was the first record of this species on the island. Also surprising was the very large number (in excess of 10,000) of Antarctic Fur Seals hauling out in late February. They are not a rare Sight on the Island any more! A detailed study of the attendance patterns of lactating cows and the corresponding weight gains of their pups was carried out.
An archaeological survey of the Corinthian Bay sealer's shanty and a botanical study of pool complexes in the north west of the Island were studies undertaken in the first month on the Island.
A great deal of effort was also put into censusing birds. A thorough survey of the distribution of all burrow nesting seabirds was completed for the Island and the population of Gentoo Penguins was counted (16,500 pairs in 60 colonies) as well as having the breeding success of their chicks recorded.
The colonies of King Penguins were recorded regularly, and appear to be continuing to increase in numbers. 1987/88 was a good season for the Heard Island Cormorant too, as 94 chicks were fledged, compared to six in 1986/87.
A large number of banded seabirds were resighted. These Included Subantarctic and Antarctic Skuas, Wandering and Black-browed Albatrosses and a Cape Petrel. Many of these birds had been banded on other islands, away from Heard Island.
Nearly all colonies of Southern Giant Petrels were visited and the counts of these colonies showed a near 50% decline compared to 1963. However, 19 breeding birds, banded as chicks in 1963, were resighted. These 25 year old birds give evidence of the long life capabilities of this species. The breeding success of a colony of Black-browed Albatrosses was also recorded.
The vegetation of the Island was mapped in detail, and growth studies carried out at a number of dispersed sites. The recognition of another possible species of grass in some newly exposed morainal areas suggests that the retreat of glaciers on the Island is creating new areas suitable for colonisation. Comparison of the vegetation of Heard Island with that of climatically less rigorous Macquarie Island promises to throw up a number of ecologically interesting insights.
Many minor projects were also completed (particularly in view of the extra month on the island due to the loss of the Nella Dan) and these included a tethered kelp experiment to discover the plants capabilities as platforms for long distance transport of marine invertebrates.
A comparison of the Collembollan (insect) populations in different habitats and the collection of funnel extracted invertebrates in some quantity may extend the species list for the Island.
Five more sealers' shanties were discovered around the Island and the artefacts in their vicinity were recorded. A detailed study of casks remaining from sealing days was undertaken, and showed that most originated from the period (1881) when the shipwrecked sailors of the Trinity were living on the island. A windlass was uncovered at low tide, after a storm on Spit Bay Beach, and was returned to Australia.
The lengthy period on the Island and enthusiastic assistance from the passengers of relief ships enabled a significant volume of debris from the old station to be picked up for return to Australia for disposal.
The tide gauge lost in 1985 was washed up on the beach and was recovered still in a watertight condition. Twelve oceanographic drift cards were found on the beaches and a complete collection of all ocean debris (other than wood) was made from the beaches. East European fishing floats were still dominant items, and indicate the fishing effort in the area up-current from Heard Island.
The 1987/88 ANARE was a long expedition for 'a summer', as nearly six months were spent on the island. But this considerable period allowed a very thorough and unusually comprehensive assessment of the status of vertebrate populations and of the distribution of plants.