Steam rises from a group of Kaimanawa horses during the biannual muster.
The Department of Conservation hopes to muster 150 or more of the wild horses and rehome them where they can be broken in.
DoC tries to keep the horse population to below 300.
At last aerial census, 469 horses were seen within the Waiouru military training area "management zone".
The herd is managed to prevent damage to the natural ecology of the area, which includes threatened plants.
Helicopters are used to muster the horses before they're sorted into groups and inspected, before being trucked to other destinations.