subantarctic islands

Restoration initiatives of ecosystems transformed by human actions require optimisation of eradication measures of introduced species, particularly in fragile insular ecosystems. We studied aspects of the spatial ecology of introduced feral cats (Felis catus) on subantarctic Auckland Island of New Zealand to assist eradication efforts of pests from this remote, biologically rich island. Firstly, we estimated home range sizes and identified core areas of activity based on movement-rooted dynamic Brownian bridge models.

Feral pigs (Sus scrofa) were introduced to Auckland Island in subantarctic New Zealand in 1807. They established and became invasive, subsequently causing substantial unwanted impacts on native biodiversity. Understanding pig movement behaviour and habitat selection can lead to focused, efficient, and effective management efforts, especially during initial knockdown of the population. Here we used location data from ARGOS telemetry collars deployed on 15 Auckland Island pigs from 2007 to 2008 to estimate seasonal homerange sizes and habitat selection.

Invasive alien species (IAS) are a recognised threat to biodiversity and ecosystem services. With increasing tourism and projected 21st century climate changes across the mid- to high-latitudes of the southern hemisphere, subantarctic islands are potentially highly vulnerable to IAS, but suffer from a dearth of baseline monitoring. Here we report tree-ring measurements from a lone exotic Sitka spruce (Picea sitchensis (Bong.) Carr) on subantarctic Campbell Island to determine past growth rates and likely future response to climate changes.

Mid to late 20th century expansion of Dracophyllum scrub into tussock grassland on subantarctic Campbell Island has been attributed to the collective effects of global warming, cessation of farming in 1931, and continued grazing by feral sheep. To determine the importance of these, we dated the timing of scrub expansion by aging 241 Dracophyllum plants in 17 plots chosen to sample the range of environments this shrub/ small tree occupies on Campbell Island.

Growth of Avena sativa L. and Agrostis tenuis Sibth was measured on peat and mineral soils from sites on Campbell Island in the New Zealand subantarctic. For the peat soils, growth was strongly positively correlated with both pH and Mg levels and less strongly with Ca and Na. With the inclusion of the mineral soil data, only the fit between growth and Ca levels was significant.