The 1987/1988 Field Season at Heard Island

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.

1987/1988年度赫德岛野外作业季
哈里·R·伯顿 南极分部野外领队

1987/1988年度赴赫德岛的澳大利亚国家南极研究探险队（Australian National Antarctic Research Expeditions，ANARE）是该岛三次夏季科考项目的最后一次（分别为1985年、1986/1987年度），科考队在岛上停留了五个半月，亦是历次驻岛时长最长的一次。1986/1987年度的科考项目以地球科学为核心主题，而1987/1988年度的科考重心再次回归生物学，一如1985年的科考；岛内非步行交通均采用LARC运载。

1987年9月18日至20日，“内拉·丹号”（Nella Dan）将由17人组成的科考队送达赫德岛，其中4人部署在斯皮特湾，其余人员驻扎在阿特拉斯湾。约一个月后的10月18日至19日，“内拉·丹号”再次到访：4名队员离岛，另有2名新队员登岛，此后岛上共有15名科考队员，直至“富兰克林夫人号”（Lady Franklin）于1988年3月2日接走全队离岛。

本次科考的核心任务之一是对赫德岛南部象海豹的繁殖种群开展全面普查。此项普查于10月中旬完成——此时上岸产仔的母海豹数量达到峰值，该时段的统计数据可与其他年份、其他岛屿的同类统计结果进行合理比对。尽管1985年曾开展过近乎完整的普查，但本次仍是赫德岛有史以来首次完成的全面种群普查。科考队步行前往长滩并完成了该区域的普查；得益于为期两天的直升机作业，科考队得以对斯皮特岛开展全域航拍——这座沉积岛海拔仅约1米，位于赫德岛东侧约1公里处，该岛栖息着数千头海豹。10月18日对该岛的一次航拍作业获取了70mm胶片影像，至此赫德岛全域的象海豹普查工作宣告完成。尽管航拍期间的强风导致部分航片无法完全重叠，但普查过程中已对少量漏拍区域进行了补正。斯皮特岛的母海豹最终统计结果为3200头±150头。

科考队还以约每月一次的间隔，对赫德岛（不含斯皮特岛）其他区域的南部象海豹开展了多次全域计数，以便将特定地点、特定日期的海豹种群数量与该区域同期的历史记录进行比对；此类计数还可量化评估海豹活动对海岸植被的破坏程度。

科考队对四湾区域的南部象海豹开展了为期两个月的每日计数，由此得以精准推算出种群数量峰值日，并获取了海豹上岸规律的详细记录，可与其他年份、其他岛屿的同类数据进行比对。1987年的种群数量峰值日为10月17日，比1985年推迟了两天。统计结果还显示，与1985年相比，四湾区域的幼海豹出生率进一步小幅下降。不过，要完成赫德岛所有海滩的海豹种群全面统计，仍需对所有数据进行细致校核。

另一项南部象海豹研究项目为断奶幼崽的体重测量工作。科考队在赫德岛东西两端各测量了约400头幼崽的体重，总样本量达821头，该数据集清晰展现了断奶期内幼崽性别比例与体重的变化规律。雄性幼崽的平均体重为116.5kg（样本量408头），雌性幼崽的平均体重为111.6kg（样本量413头）。该数据可与其他岛屿的断奶幼崽体重数据进行直接比对，由此或可揭示为何部分海域（印度洋区域）的海豹种群数量出现下降，而另一些区域（南乔治亚岛）则未出现此类现象。

60头刚上岸换毛的南部象海豹被麻醉后接受了体长测量与体重称量，随后通过软橡胶软管以水流冲洗的方式采集了其胃容物样本。采集到的胃容物中可见明显的鱿鱼喙与胃线虫样本，但仍待进一步分析；该研究将首次获取赫德岛区域南部象海豹饮食结构的详细数据。

科考队对所有目击到的豹海豹进行了计数，在部分海滩（2月下旬），豹海豹的数量甚至超过了南部象海豹。35头豹海豹被麻醉后接受了体长、体重测量，随后被打上标签并采集了血液样本。

科考队意外发现了2头带有马里恩岛（Marion Island）标记的亚南极海狗，这是该物种在赫德岛的首次记录。同样令人意外的是，2月下旬上岸的南极海狗数量超过10000头，如今它们在赫德岛已并非罕见物种。科考队还开展了一项详细研究，聚焦哺乳期母海豹的上岸规律及其幼崽的体重增长情况。

登岛首月，科考队开展了两项研究：对科林斯湾海豹猎人棚屋的考古调查，以及对赫德岛西北部池沼群的植物学研究。

鸟类普查也是本次科考的重点工作之一。科考队完成了赫德岛所有掘洞营巢海鸟的分布普查，统计了巴布亚企鹅（Gentoo Penguin）的种群数量（60个繁殖群，共计16500对），并记录了其雏鸟的繁殖成功率。国王企鹅繁殖群的监测工作定期开展，结果显示其种群数量仍在持续增长。1987/1988年度对赫德岛鸬鹚而言也是丰收季，当年共有94只雏鸟成功离巢，而1986/1987年度仅为6只。

科考队多次目击带环志的海鸟，包括亚南极贼鸥、南极贼鸥、漂泊信天翁、黑眉信天翁以及1只海角海燕。其中多数海鸟的环志来自赫德岛以外的其他岛屿。

科考队几乎探访了所有南方巨鹱的繁殖群，统计结果显示，与1963年相比，其种群数量下降了近50%。不过，科考队再次目击了19只1963年作为雏鸟被环志的成年个体，这些25岁的个体证实了该物种具备超长的寿命。科考队还记录了一处黑眉信天翁繁殖群的繁殖成功率。

科考队对赫德岛的植被开展了详细制图，并在多个分散点位开展了植物生长监测研究。在部分新近裸露的冰碛区域发现了疑似新的禾本科植物物种，这表明赫德岛冰川的退缩正在形成新的可被植物定植的区域。将赫德岛植被与气候条件更为温和的麦夸里岛（Macquarie Island）植被进行比对，有望获取多项具有生态学价值的研究结论。

此外，科考队还完成了多项小型研究项目——鉴于“内拉·丹号”失事导致科考队在岛停留时间额外增加了一个月，此类项目得以顺利开展。其中一项实验为大型褐藻附着实验，旨在探究该植物作为海洋无脊椎动物长距离运输载体的能力。对不同生境中弹尾虫（Collembola）种群的比对研究，以及批量采集漏斗诱捕的无脊椎动物样本，有望扩充赫德岛的物种名录。

科考队在赫德岛周边又发现了5处海豹猎人棚屋，并记录了其周边的人工制品。科考队对海豹捕猎时代遗留的木桶开展了详细研究，结果显示多数木桶产自1881年——当时“特里尼蒂号”（Trinity）的失事船员正定居于赫德岛。斯皮特湾海滩遭遇风暴后，科考队在退潮时发现了一台起锚机，随后将其运回澳大利亚。

得益于较长的驻岛时间以及补给船乘客的热心协助，科考队收集了大量旧科考站的废弃物，运回澳大利亚进行集中处理。1985年遗失的潮位计被海浪冲上海滩，科考队将其回收时，该设备仍处于防水完好状态。科考队在海滩上发现了12张海洋漂流卡，并收集了海滩上所有非木质海洋废弃物。东欧产的渔用浮标仍是海滩废弃物中的主要品类，这表明赫德岛上游洋流区域存在大量渔业作业活动。

1987/1988年度的ANARE科考队虽为夏季科考项目，驻岛时长却近六个月，堪称超长科考。不过正是这段充裕的时间，使得科考队得以对赫德岛的脊椎动物种群现状与植物分布情况开展极为全面且细致的评估。