Deer eradication on Secretary Island

By Norm Macdonald, Senior Ranger, Te Anau.

In August, two of the last remaining deer on Secretary Island, in Fiordland’s Doubtful Sound, were culled by DOC’s Secretary Island hunting team. Since 2006 approximately 700 deer have been removed from the island.

Secretary Island

A deer-free Secretary Island will be a haven for native plant species that are vulnerable to deer, including native ferns, broadleaf, mahoe and kamahi.

The eradication also forms part of the wider Secretary Island Restoration programme, with the long term aim to reintroduce threatened species.

I have a long history of managing these kind of eradication projects in both New Zealand and internationally. Despite this, when I arrived in Te Anau two years ago and saw how rugged and steep Secretary Island was, I knew that this eradication would probably be the most challenging project I have had to manage so far.

A deer caught on camera

With a combination of great teamwork, learning from our mistakes, and not being afraid to try different approaches, we have made significant progress in our ability to detect and eliminate deer at very low densities over the last two years.

A high priority for our hunting team was the diligent collection of DNA samples from any deer droppings that they come across on Secretary Island. The samples allow us to identify each animal’s sex and unique DNA profile. This has allowed us to build up a profile of the population numbers on the island.

By August this year we were confident that only four deer remained on Secretary Island—one hind and three stags. A joint effort between DOC, local contractors, expert tracking dog handlers from Te Urewera, and Te Anau Helicopters was launched to try and find these last known individuals.

We used the hunting team to systematically cover the island and flush out the hind, which was then shot from the helicopter. This deer was subsequently found to be pregnant.

Two of the team’s hunting dogs with one of the deers

The removal of the last known hind is a significant milestone for the eradication programme as it eliminates the potential for fawns to be born on Secretary Island. The team also found and killed a large stag after tracking it through the island’s rugged terrain and coastline.

We are now fairly confident that there are only two deer left on Secretary Island. However I won’t get too cocky with that estimate until we are certain that the last deer has been despatched.

DOC’s Secretary Island hunting team