Dispersal of southern elephant seals (Mirounga leonina) from Davis Base, Antarctica: Combining population genetics and tracking data

Marine animals such as the southern elephant seal (Mirounga leonina) rely on a productive marine environment and are vulnerable to oceanic changes that can affect their reproduction and survival rates. Davis Base, Antarctica, acts as a moulting site for southern elephant seals that forage in Prydz Bay, but the genetic diversity and natal source populations of these seals has not been characterized. Determining the genetic diversity of moulting populations like this one provides essential information on seal dispersal, inter-population mixing, and foraging behaviours. In this study, we combined genetic and animal tracking data on these moulting seals to identify levels of genetic diversity, natal source population, and movement behaviours during foraging and haul-out periods. Using mitochondrial sequence data, we identified two major breeding lineages of seals at Davis Base. We found that the majority of the seals originated from breeding stocks within the South Atlantic Ocean and South Indian Ocean. One seal was grouped with the Macquarie Island breeding stock (South Pacific Ocean). The Macquarie Island population, unlike the other two stocks, is decreasing in size. Tracking data revealed long-distance foraging activity of the Macquarie Island seal around Crozet Islands. We speculate that changes to the Antarctic marine environment have resulted in a shift in foraging and dispersal strategies, which subsequently affects seal population growth rates. These findings have implications for conservation management plans aimed at improving the population status of the southern elephant seal.

Differing ecological responses of seabirds to invasive species eradication

The impact of invasive species at seabird breeding islands causes a breakdown of important ecological functions such as prey consumption and nutrient transfer, and elevates extinction risk in impacted taxa. Eradicating invasive species from islands can result in substantial short-term recovery of seabird populations and consequently the prevalence of eradication programs as conservation tools is increasing. However, as the scale and complexity of eradications has increased, quantitative data on rates of recovery, especially from larger islands, remain limited. Furthermore, the mechanisms that govern recovery are poorly understood, limiting our ability to forecast outcomes and therefore prioritise effectively. Here, using the world's largest multi-species vertebrate eradication from Macquarie Island as a case study, we show how responses to invasive species and their eradication differ. Species with broad realised niches whose breeding phenology minimizes time on land and corresponds with summer resource abundance remained extant alongside invasive species while more habitat-specific species present in winter were extirpated. Following eradication, immigration and flexibility to colonise under-utilised optimal habitat appears to be boosting population growth in recolonising species, whereas established populations appear to be tethered to refugial habitats by the influence of philopatry, and their recovery is slower as a result. Unpicking these differential responses and the mechanisms behind them provides valuable information to help predict responses in other systems as future eradications are planned.

Mawson’s views on use of natural resources in the Antarctic and sub-Antarctic

Sir Douglas Mawson is a well-known Antarctic explorer and scientist. Early in his career, he recognised opportunities for commerce in Antarctic and sub-Antarctic regions. While at Cape Denison, Antarctica, in 1913 on the Australasian Antarctic Expedition (AAE), the Adelie Blizzard magazine was produced. Mawson contributed articles about Antarctic natural resources and their possible use. Later, he advocated Australia be involved in pelagic whaling. He collected seal skins and oil for their commercial value to be assessed by the Hudson’s Bay Company. During the AAE, Mawson visited Macquarie Island where an oiling gang was killing southern elephant seals and royal penguins. Mawson was concerned that they were over-exploited and lobbied successfully to stop the killing. His plans for Macquarie Island included a wildlife sanctuary, with a party to supervise access, send meteorological observations to Australia and New Zealand, and be self-funded by harvesting elephant seals and penguins. Macquarie Island was declared a sanctuary in 1933. Although Mawson has been recognised as an early proponent of conservation, his views on conservation of living natural resources were inconsistent. They should be placed in their historical context: in the early twentieth century, utilisation of living natural resources was viewed more favourably than currently.

Assemblages of myxomycetes on subantarctic Macquarie Island and tropical Christmas Island

Christmas Island and Macquarie Island are two isolated islands of essentially the same size but providing very different environmental conditions for myxomycetes. The former is located in the tropics and the latter in the subantarctic. Surveys for myxomycetes carried out on Christmas Island in 2017 and Macquarie Island in 1995 yielded a total of 85 species. These data were published in two previous papers, but these papers did not consider the biogeographical distribution of all of the myxomycetes recorded from the two islands. Christmas Island and Macquarie Island share only nine species in common. Two of the 26 species recorded from Macquarie Island and one of the 68 species recorded Christmas Island were new to science.