A successful muster of Kaimanawa horses has had 88 moved to approved homes and another group of mares put into a contraception programme to limit herd growth and reduce environmental impacts.
The muster, held annually following the advice of the Kaimanawa Wild Horse Advisory Group to manage the herd at sustainable levels within the Waiouru Military Training Area, allows the horses in the wild to maintain best condition and protects the fragile ecosystems unique to the Moawhango Ecological Region.
Department of Conservation Central Plateau operations manager Dave Lumley says rehoming is fundamental to the success of the programme, but other tools are being implemented to increase sustainability.
"Over the next few years, we will continue to administer contraception to some horses and monitor the success of the programme. Keeping the horses healthy and at sustainable levels is what everyone wants."
Kaimanawa Heritage Horses Welfare Society (KHH), which is responsible for rehoming efforts, agrees.
Spokeswoman Sue Rivers says rehoming and its associated limitations are frustrating and not sustainable as the only long-term management option.
"Over a decade of extensive research and drive has gone into seeing the contraceptive option implemented so we are incredibly proud to see our efforts have meant this alternative has become a tool to help reduce both population growth and the need for rehoming musters."
The contraceptive is injected by qualified veterinarians and will suppress fertility in adult mares for up to four years.
Dave says DoC is grateful to KHH for its significant contributions to the process of managing the herd.
"We're fortunate to have enduring partnerships with groups like the KHH, the military, SPCA and others to ensure we have a robust and sustainable management plan.
"Working together means we will see healthy Kaimanawa horses in the wild into the future."
One of the founding aims of the Kaimanawa Heritage Horses Welfare Trust was to preserve a wild horse population with minimal intervention. However, the population growth rate of Kaimanawa horses has meant rehoming musters have become an annual event.
This creates an enormous workload for the volunteers of KHH, DoC staff and the NZ Defence Force. Essentially, until now horses have been allowed to breed only to be mustered and rehomed. This has always been an unsustainable method of herd management.
Since 2009, an effort has gone into looking at more-sustainable and long-term options to slow the rate of population growth, and eventually reduce the number of horses requiring rehoming, in addition to reducing the frequency of the musters.