Rabbit exclosures success for native biodiversity

Funding from Biodiversity Hawke’s Bay enabled six rabbit exclosure plots to be built at Puahanui Bush in 2019 to measure the impact of rabbit browsing on this significant podocarp forest.

“Damage caused by rabbits and hares has long been acknowledged to be a major contributor to the decline of native vegetation in New Zealand,” says Puahanui Bush project manager and ecologist Kay Griffiths, however, there hasn’t been a lot of data recorded specifically about the impacts on shrublands or forest.

“Rabbits will eat virtually any plants when hungry, but prefer seedlings and saplings, and like many browsers will eat the most palatable first,” says Griffiths.

The experiment, the first of its kind in Hawke’s Bay, compared six 2.5m x 2.5m paired plots (open and closed areas) randomly throughout the 130ha Central Hawke’s Bay forest.

Biodiversity Hawke’s Bay general manager Debbie Monahan says this project is a great example of how we can support local community initiatives to get off the ground. Kay is passionate about biodiversity and committed to the restoration of the Puahanui Bush and it’s an honour to support the Gwavas - Puahanui Charitable Trust in the work they do to manage and restore the bush.

“Data from the plots, remeasured after one year, confirmed our observations, that rabbits and hares are having a measurable impact on seedling recruitment and survival within Puahanui Bush,” says Kay Griffiths. While deer and pigs are also likely to be having an overall impact on seedling and sapling recruitment and survival, rabbits are currently the most numerous of these browsers.

Ms Griffiths says that the data shows a trend of loss of species density and diversity in the open plots. Without control of rabbits, it is likely that this general trend of loss of species diversity and loss of seedling recruitment and survival will affect the long-term regeneration processes that are usual in a fully functioning forest ecosystem.

“The results and this data have been instrumental in confirming the observations we have seen on the ground,” says Griffiths.

“To ensure these ecosystem processes are re-established within Puahanui Bush, rabbits must be controlled to zero density within the Bush,” says Griffiths.

Kay Griffiths will be including the data collected in this experiment to support applications for additional funding for rabbit proofing and control in the Puahanui Bush.

Photo: Landowner Phyll Gibson in the exclosure looking at the growth of seedlings

Photo credit: Kay Griffiths

19 April 2022

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