The extinction of native species
The presence of exotic rodents on islands is one of the greatest causes of plant and animal species extinction in the world.
Rats have been implicated in the extinction of five endemic bird species, at least 13 species of endemic invertebrates, and two plant species on Lord Howe Island (LHI).
Rodents are also a recognised threat to at least 13 other bird species, two reptile species, 51 plant species, 12 vegetation communities, and seven species of threatened invertebrates on the island. Seven of these species are listed as "Critically Endangered" under NSW and Commonwealth legislation.
As a significant threat to Lord Howe Island's World Heritage values, the removal of rodents has since resulted in significant benefits to the island's biodiversity, allowing species recovery, as well as improved visitor and community experience.
Ratting out the rodents
LHI is the largest permanently populated island on which the eradication of rodents has been undertaken to date.
The LHI Rodent Eradication Project (REP) is the Island's single biggest conservation action to date. The project aimed to eradicate introduced rodents: the Ship Rat (Rattus rattus) and the House Mouse (Mus musculus) from LHI and its associated islands and rocky islets (excluding Balls Pyramid), known as the Lord Howe Island Group (LHIG).
The eradication of rodents also presented an opportunity to simultaneously eradicate the introduced Masked Owl.
After more than 15 years of detailed research and planning, the final stage of the LHI REP was implemented between May and December 2019.
Residual rats - 2021 Rodent Response
In April 2021, after 16 months without sightings of live rodents, a rat was sighted in the settlement area by a community member and a rodent response was activated.
The 2021 response revealed new, world-first learnings about the social behaviours and resistance of rodents.
It has since been determined through genetic testing by the Australian Museum Research Institute that these rats were descended from a very small number of rats that existed prior to the 2019 eradication.
The Island’s monitoring network was upgraded as a result of the response.