Earlier this year I returned from hiking and cycling in New Zealand where there is currently a concerted effort underway to eradicate the Australian brushtail possum, along with several other pest predators.
So how did possums become such a pest in New Zealand? Well, it all dates back to 1837 when introductions were attempted for the fur trade. By 1858 possums were successfully introduced. Numerous batches were released such that by 1930 they had been released at over 450 locations around the country. Initially they were protected to allow their numbers to build up. By 1946 all protection was removed and they were recognized as a noxious pest. Their numbers are estimated to be 50 to 70 million – that’s more than the number of sheep found in New Zealand.
Possums consume vegetation at night focusing on some of the tall canopy species (including flowering trees such as rata and pohutakawa) eating new shoots and flowers. Over time they can change the dynamics of the forest. Possums also impact native wildlife eating eggs, chicks and adults of native bird species and competing with birds for food resources and nesting sites. Impacts on bats and invertebrates have also been recorded. Possums in New Zealand also carry bovine tuberculosus (TB) which poses a threat to the cattle and deer farming industries.
New Zealand has vowed to eradicate possums, along with several other pest predators, by 2050. We saw plenty of evidence for use of poisons on our travels and heard of the controversies over the use of 1080 poison.
Check out Nature’s news feature “Behind New Zealand’s wild plan to purge all pests” for further information. [Nature 541, 148-150 (12 January 2017) doi:10.1038/541148a].