The Ark has been steadily expanding, since the original area was established in 2003. It now covers approximately 2300 hectares.
The area shown in yellow was added with urgency, to protect the kokako released in 2009, who settled in what was then an unprotected area south of the Dam Road. The bait stations in this area are distributed in a less concentrated 100x100m grid, compared to the 50x100m grid previously used. The effectiveness of this less intensive control will be monitored and compared to the control obtained in the other part of the Ark.