A collective predator control effort over the past 15 months has helped to lower rat and stoat numbers – a positive sign for native birds in the area.

The collaborative efforts by conservation groups Southern Lakes Sanctuary, Department of Conservation, and Central Otago Lakes branch of Forest and Bird have curbed the ‘rat plague’ of the 2023/24 summer by installing over 700 bait stations, servicing more than 1400 traps, and undertaking a 1080 operation by DOC, across the Makarora area over the past 15 months.

And, much to the delight of all involved, a family of endangered whio (blue duck) with five youngsters have been observed on the southern end of the Young River over recent months.

Southern Lakes Sanctuary project director Paul Kavanagh says the whio sighting is excellent news following the localised conservation work.

“The presence of whio in the Young River is an optimistic sign that indicates good stoat control in the area, which comes down to the great collaborative effort last summer,” he says. “These endemic manu (birds) nest on the banks of rivers, in caves or in dense vegetation, and nesting whio are very vulnerable to stoats.”

Central Otago Lakes Forest and Bird chairman Andrew Penniket says extensive trapping is one of the factors for the increased presence of the birds.

“The whio family has been seen over the space of a month by several groups and is the largest number seen on this river, or in our catchments, in our collective memories,” he says. “The sightings are a wonderful reward, coinciding with the work undertaken to put an extra 20 traps into the southern end of the Young River, specifically for the protection of rock wren and whio.

“It has been heartening that we have had very low catch rates of rats and stoats on all our trapping lines. It is probably the lowest ever, that I can recall,” Penniket adds.

In the summer of 2023/24 rat numbers exploded due to a ‘mast season’ of native beech trees, where a larger number of tree seeds are produced. A mast season generally occurs every two to six years and results in a dramatic increase in rat numbers, and then stoats.

The collaborative predator control effort has achieved positive results for other species in the area.

“We were concerned about the survival of the endangered mohua (yellowhead) with the siege of rats swarming to the area last spring and summer,” Kavanagh explains. “However, in the core trapping and bait station areas, most of the mohua chicks that we have monitored have survived in both this year's and last year’s breeding seasons."

This area is a priority site for the Department of Conservation’s National Predator Control Programme and as such received landscape scale predator control via aerial 1080 in March 2024, in response to rodent plagues following beech masts. Working in partnership with DOC ensures the best outcome for predator control.

“The mohua and whio survival shows the power of working together,” Kavanagh says. “The amazing efforts of volunteers and staff, who strapped on their tramping boots and frequently checked and cleared thousands of traps and bait stations. Collectively, they contributed thousands of hours towards this important mahi to protect wildlife in Makarora.”

Introduced predators such as rats and stoats kill more than 25 million native birds and wildlife every year in New Zealand. An estimated 1382 rats were dispatched in traps and an estimated 3600 rats from the bait station network alone, in Makarora between November 2023 – November 2024.

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