Raukumara deer control
Date: 03 April 2008
A 2007 survey of deer numbers in Raukumara Forest Park has led to the Department of Conservation (DOC) testing a new model for controlling animal pests in native forests. DOC Technical Support Officer, Dave Carlton said today that last year's survey showed that not only are deer numbers increasing, but they are reaching the point of causing irreversible damage to the forest.
"Historically, pest animal numbers in Raukumara Forest Park have been very low, and this has allowed native plants to thrive. The forest structure and variety of plant species has been remarkably good," Mr Carlton said.
When deer began to colonise the Raukumara Forest Park, it was in the same period that the venison recovery industry was getting established. The consequent pressure of hunting kept deer numbers low, particularly east of the Motu River. The result is that Raukumara forest east of the Motu still contains a shrub tier of plants that are palatable to deer. This differs from most North Island forests where deer are present.
The 2002 collapse of the wild venison recovery industry has removed a significant control on Raukumara deer numbers, leading to concerns that the shrub tier could be at risk. In the 2007 DOC survey of forest health and deer numbers, the significant damage to the shrub tier was obvious. It was also clear that without intervention, the shrub tier will soon be lost.
"To prevent loss of the shrub tier, DOC has contracted a helicopter company specialising in deer control to focus their venison recovery operations within Raukumara Forest Park. An Opotiki helicopter operator supplied a successful tender to remove deer from the park over the next year. By recovering and selling the deer, the operator will remove a pest at a lower cost than would be the case if we used a search and destroy operation. The operation will be trialled for three years to measure its success before further decisions on long term management can be made," Mr Carlton said.
Opotiki Programme Manager Lindsay Wilson who co-ordinates the local teams of DOC animal pest control operators said that the new system of keeping deer numbers in check is being closely watched by other areas.
"For DOC, the aim is to protect forest by reducing pest numbers. Essentially a private operator is subsidising a DOC pest control operation and if the price of venison lifts, there is potential for DOC to pull back altogether and leave this work entirely to private operators," Mr Wilson said.
Removal of the shrub tier from forest has numerous long term consequences for the health of the forest and the wildlife it contains. In country as steep as Raukumara Forest Park, there is an immediate threat of increased erosion that can have major downstream effects. Bird and insect life that is dependent on a good variety of plant species also suffers without young plant growth.
"Sadly, many people imagine that the relatively sparse undergrowth that exists in New Zealand forests that contain deer is natural. Raukumara Forest Park provides a clear demonstration that it is not. This is our opportunity to ensure that a vital part of long-term forest health does not disappear as it has in so many other areas of New Zealand," Mr Wilson said.