The Importance of Islands
The cane toad was introduced into Australia in 1935 when 101 cane toads were brought from Hawaii to Queensland.
We know exactly the evening two entomologists who worked for the Hawaiian Sugar Planters’ Experiment Station, Cyril Pemberton and Harry Dennison, accompanied Reginald W. Mungomery, an employee of the Queensland Bureau of Sugar Experiment Stations (BSES) around Honolulu, collecting cane toads for import into Australia. Pemberton was a significant figure in the transnational pathway of the toad: he was responsible for introducing the toad to Honolulu from Puerto Rico. On the evening of the 1 June 1935, a whole host of Australian animals fate would be sealed.
A highly toxic toad that was completely unable to climb to the height to reach the Frenchi or Greyback beetles that was damaging Queenslands sugar cane plantations was now on its way to Australia. On 22 of July 1935 the 101 toads arrived in Australia. By 19 August 1935 the numbers of toads which had been kept in captivitity had reached 2400. The cane toads were released, took one look at those beetles, and started hopping in all directions.
The toad began a relatively slow march north, south and west, advancing 10 kilometres a year. In recent times however, the march has become a sprint, and a rate of 50 kilmetres per year now being identified. It appears that the toads are evolving to move faster to fill the vacant spaces that haven’t already been claimed by the toad.
In 2001, the toad hit Kakadu National Park. By 2003, northern quoll numbers, who have been an integral part of northern Australia’s ecosystem for millions of years, plummetted. There was now a very real threat of extinction of the northern quoll as a direct result of its interaction with this single species.
In a rare display of timely Government intervention, the northern quoll was listed as Endangered under Australia’s Environment Protection and Biodiversity Conservation Act and plans were developed in conjunction with the local aboriginal landowners to relocate a 64 quolls to the Pobassoo (19 quolls) and Astell Islands (45 quollls), off the coast of Arnehm Land.
Despite a devestating cyclones and bushfires, by the end of 2007 there were around 5600 northern quolls enjoying their new toad-free island home.
While there are inherent issues with inbreeding depression for example, with any population isoloated for multiple generations, the quoll is safe, at least in the short term.
So could our islands be better utilised to protect some of our rarest species, until we’ve got a handle on the environmental issues that plague mainland Australia? Australia has 8,222 various sized islands within its maritime borders. So that is essentially, thousands of sanctuaries that are either free of the key threatening processes that harm so much our wildlife (cats, foxes, dogs, cane toads, rats, disease) or could be made pest free with relative ease, if we directed our attention to them a little more.
The good news is, is that the use of islands to protect species has seen somewhat of a revival since the northern quoll translocation project commenced.
Tasmania’s Maria Island has been the stage for the recent introduction of an insurance population of Tasmanian devils. An argument against using islands for introducing apex predators like the quoll or devil is that they may impact on the species already on the islands, or, if captive bred, will not be able to revert to wild behaviours.
However, with any reintroduction, there will always be an element of active management. Of ensuring population densities do not exceed the carrying capacity of the island, and further relocations to reduce stocking levels if it is deemed necessary. It’s also probably a good idea to ensure that the islands are selected based on a rough geographical alignment with the species being introduced. The Kawau Island off New Zealand had 5 wallaby species introduced to them in the 1870s – 4 surviving until today. Of these, 2 are classified as Threatened or Endangered with extinction in Australia. However, bringing them all the way back to their homeland is a little more challenging than just a small boat ride.
With respect to the loss of wild behaviours anticipated by some observers, the experience gained by the Save the Tasmanian Devil Program, it suggests that there were only very small and short-term differences in that the more intensively managed animals lost body weight at a higher rate than others, but then picked it up after that. These subtle differences all but disappeared after a few months, with devils reverting to wild behaviours better than could have been anticipated.
Experience has shown that Authorities should place a greater focus on using our islands for the protection of some of our most endangered species.