Over the previous two summers, it was perfect weather conditions – a hot 2016-2017 followed by a cold 2017-2018 – that saw plants and trees across the country produce enormous amounts of seed and fruit this year, creating a so-called mega mast. Rat numbers around many areas of New Zealand exploded. Rats breed more quickly when there is a plentiful supply of food for their young, but when that food runs out, they turn to vulnerable birds.

We were hoping to fly into Ikawatea, an area of Ruahine Forest Park renowned for its dense forest, deep valleys and steep climbs, to monitor the rat population. Such monitoring needs to be done before any 1080 operation can be conducted. A survey in the north of Ruahine Forest Park in May showed overnight rat activity at 61 per cent. This triggered planning for a 1080 operation and we were going in for a final count before a probable drop.

The weather eventually cleared, so our patience paid off.

We radioed Simon and were soon sailing through clear skies, past Aorangi, over the Ruahine Corner tussock land and down into the deep valley sheltering Ikawatea Forks Hut. We were dropped off just after three, but, although we tried, we were unable to visit all the monitoring stations before dark.

From the map it had seemed pretty doable to me, but I can be very naive sometimes.

We dumped our packs at the hut. I grabbed my cameras and a light bag, the others divvied up the Black Trakkas – the inkpads that count rat activity – and we were off.

Pete disappeared up a steep ridgeline that heads south-west toward Ruahine Corner, Tamara and I took an eastward track that leads to No Mans Hut. I’ve done plenty of monitoring, trapping and tramping in the Ruahines, so I thought I knew what I was in for as we started up the ‘hill’.

I was soon trailing a long way behind Tamara.

Eventually, she dropped her pack and we took off our jackets during the brief break. But after an alarmingly short time, we were climbing again. On the map, the monitoring lines were really close. In reality, they were hauntingly difficult for my 54-year-old heart to reach. By comparison, it was Tamara’s 29th birthday and she powered out in front, leaving me feeling my age.

She finally called a halt and pointed: “The first line is just over there.”

“How far away is the second one?” I gasped.

“About 900m.”

Now, if I was going to be walking to the dairy for a mince pie, 900m wouldn’t be that far. But 900m on a seemingly vertical track bears a closer relationship to climbing Everest than a walk to the dairy.

We agreed that Tamara should go on and set out the first lot of tracking tunnels without me. I would wait on the track and recover. She would come back and we’d do the first lot together.
While I waited, Pete arrived and radioed to Tamara that he and I would check the last line of tracking tunnels to save time.

“We’ll probably be crossing the river to the hut in the dark,” he said. In other words, we didn’t have time to muck around.

As we motored through the undergrowth of pepper trees and bush lawyer in the beautiful evening light, the forest seemed to glow. Pete’s uniform and the plants radiated iridescent green. Glimpses of luminous orange berries tempted me.

In a flash, Pete set 10 tunnels with peanut butter and ink pads and we were back at the track with Tamara. In another flash, we were all back at the hut. A slow Ruahine climb makes for a quick Ruahine descent.

We celebrated Tamara’s birthday with a smokey fire, gingernuts and a perfectly-cooked steak. As a whio called in the dark river below the hut, we made our beds for the night and our plans for the next day.

Pete volunteered to check all of the tunnels the following day, while Tamara and I climbed the ridge to the Mangaohane Plateau and reset a line of DOC200 single set traps. I’d worked this line eight months earlier and we’d pulled a small number of rats out of it. This time about 80 per cent of the traps had a kill.

Initial analysis of the results collected by Pete – known as the Tracking Tunnel Index (TTI) – found overnight rat activity at 74 per cent. The technical term for this is an ‘irruption’. But I think I’ll call it a plague. A 0-10 per cent rate on the TTI is considered ‘acceptable’.

A mast year doesn’t just create lots of rats – it’s great for birds, too. One of the highlights of the trip for all of us was the amazing birdlife. The area is trapped by a dedicated group of volunteers, but it also had the benefit of a 1080 drop in 2017. Good numbers of whitehead (flocking in huge groups), riflemen, tui that chattered like kākāriki, kereru, warblers and fantails followed us as we worked. We heard the rarer whio and plenty of robins. Pete watched a kārearea swoop above the hut.

Because the northern 30,000ha of the Ruahine Ranges is deemed to be a place of high biodiversity value, the threat the current rat irruption poses means that it qualifies for inclusion in the 2019 Tiakina Ngā Manu 1080 (formerly Battle for Our Birds) operations.

After the 2017 Battle for Our Birds operation in the area, rat monitoring showed activity down to less than one per cent. All going well, there will be a repeat this spring.