Hinau fruit indicate Mast Year underway

The abundance of hinau fruit in East Harbour Regional Park is indicating a significant Mast Year is underway as predicted, according to environmental scientists.

For the past 10 years the Greater Wellington Regional Council Environmental Science team have been using the amount of hinau fruit present to predict the severity of the seasonal threat of pest animals is in the area.

Greater Wellington Senior Environmental Monitoring Officer, Barrett Pistoll, says at this time of year hinau fruit make up a large part of the diets of rodents and other pest animals.

"When we have a bumper fruiting year, it leads to an explosion in the number of pest animals in our forests."

Barrett says the assessment of fruit shows the extent to which rats, possums and other pest animals are thriving and causing damage to our native wildlife and native plants.

"Over the past 10 years we have monitored the same 10 trees at the same time of year so we can make comparisons to previous years and determine the potential numbers of pest animals this season.

"This is the second highest producing year on record behind 2014 which was a significant mast event," Barrett says.

A mast event is when trees produce extremely heavy flowering and fruiting which serves as food for pests, causing a boom in rat and stoat numbers.

"The Greater Wellington biosecurity team will carry out some more extensive pest control in the area in a couple of weeks, minimising the impact on native flora and fauna," Barrett says.

The team will use bait stations containing Feracol and Ratabate to combat growing pest numbers.

"Once the rodent numbers increase to high levels, many native birds can't survive. Generally we can keep pest numbers low, but during a mast event extra methods are required," Barrett explains.

The team also monitors 20 Hinau trees in the Wainuiomata/ Orongorongo Catchment Area - the results of which are currently being evaluated.