The current status of wombat populations on Maria Island National Park

During the late 1960’s to early 1970’s a collection of native species were introduced to Maria Island, including marsupial herbivores. The Forester kangaroo was introduced partly to act as the major grazer on the island and partly for conservation reasons. Common wombats were also introduced, another major grazer. Forester kangaroo numbers have declined in recent years due to a combination of impacts from: limited recruitment due to low rainfall; interspecies competition for food resources; and, historical culling. Biological monitoring undertaken in April 2015 indicated poor body condition for Forester kangaroos, despite not being culled since 2012. In contrast, the common wombat population has been rapidly increasing, particularly in the south of the island, to the point of out-competing the Forester kangaroo for resources in the area.

Intense grazing pressure is evident at sites dominated by common wombat grazing. Common wombats are frequently viewed digging for roots, which is typically a sign of nutritional stress. The presence of scabies mites has also been confirmed in the common wombat population on Maria Island since 2011. Scabies mites are responsible for directly causing the infection, sarcoptic mange, which has had devastating impacts on common wombats at Narawntapu National Park. Common wombats are also susceptible to toxoplasmosis and may carry herpesviruses, both of which will adversely affect body condition. As a result, there is an increased risk of diseased animals being in contact with the visiting public on the island. The exact genetics of the common wombats on Maria Island is also completely unknown due to the Flinders Island subspecies being introduced in the 1970’s.

The purpose of this report is to determine the current status of common wombats on Maria Island, based on scientific evidence of a rapidly increasing population trend. The impacts of this trend include: intense grazing pressure in all wombat dominated sites; interspecies competition with Forester kangaroo at the same sites; and, the potential for a lethal outbreak of sarcoptic mange in the future. Regular monitoring of Tasmanian devil scats has indicated that common wombats are a component of the devil diet. However, there has been no impact on common wombat population trends since the devil introductions, and there is no evidence that devils prey on adult wombats, either on Maria Island or the Tasmanian mainland.