Main Club, 7 November 2025
Two speakers, Drs. Andrew Burbidge and Ian Abbott gave the talk at this meeting. Both have been research scientists in WA Government departments, and held administrative positions there. Dr Burbidge is Chair of the WA Threatened Species Scientific Committee and of the Barrow Island Gorgon Gas Development Quarantine Expert Panel. Ian Abbott has worked as a research scientist in the field of island biogeography.
Ian is a self-proclaimed “nesophiliac” (lover of islands). There are about 3500 islands off the coast of WA, most off the Kimberley coast, the biggest being Dirk Hartog Island. Many of these form part of nine archipelagos, ranging from the Buccaneer in the Kimberley to the Recherche near Esperance. Most of them are continental islands – those that formed when sea level rose about 7,000 years ago – but there are a few coral cays as well, and some are tied – islands connected to the mainland by a sandspit.
“Island syndrome” includes low species richness, greater endemism, prodigious abundance, genetic and behavioural changes, gigantism or dwarfism, and habitat differences. Excess of guano from nesting seabirds can produce lush vegetation or kill plants. Long periods without fire can lead to significant ecological differences. On many islands, Europeans have hunted seals, introduced exotic plants and animals (deliberately or not), and brought the effects of tourism. There are also biogeographic differences, even between islands that are close and similar, such as Rottnest and Garden Islands, which have different species of snakes and mammals, for example.
Andrew then talked about conservation values. Some mammals would be extinct if not for the protection from predators that islands can provide. Luckily, Fairy Terns nest mostly on islands. On some islands, several tern species coexist because some nest in trees, others in shrubs, and some on the ground. Bigger islands can support more mammal species. The Nabarlek (Petrogale concinna) thrives on four Kimberley islands, and the Golden Bandicoot on nine. Both are nearly extinct on the mainland.
Invasive species pose a significant management challenge. Cats and rats alone have brought many species of seabird to local extinction. Feral cats eat small to medium-sized mammals and hatchling turtles on some islands. Other pests include foxes, rabbits, sheep, goats, rats and mice. The Black Rat can occur even on tiny islands with reefs. If cats are eliminated, the numbers of rats and mice rise. Helicopters have been used to spread rodenticide, and conservation staff have been known to spend their holiday time helping with eradication projects on islands. Cat eradication is achieved through baiting and trapping (e.g., on the Montebellos).
WA is a leader in the introduction of animals to islands – either reintroducing previously existing species or introducing animals to islands to protect them from predators. A successful example is the return of the Rufous Hare Wallaby to Dirk Hartog Island National Park. In this ex-pastoral lease, pest eradication and nine reintroductions have been undertaken, as well as the restoration of vegetation.
Andrew said that more data, more funding and more island managers are needed in order to continue the work of restoring the ecosystems on our islands.
Mike Gregson
