In search of the carnivorous snail

Department of Conservation —  17/03/2015

By Timothy Maule, Trainee Ranger, Turangi

DOC Central Plateau and Project Tongariro staff went bush recently for a snail-counting mission in the Waipakihi Valley.

DOC Central Plateau staff and Project Tongariro in the Waipakihi Valley.

The team on the giant snail trail

Ripping up the Waipakihi in a chopper with a pack full of gear, one dog, some rifles and enough food to feed a tribe for eight days seemed too good to be true. Up Thunderbolt Creek, along the tops, drop down into the Rangitikei, then down to the Otamateanui confluence.

For eight of us, this was going to be our home for the next eight days, as we descended on the area to monitor about 40 ten by ten plots for our local carnivorous snail, Powelliphanta Marchanti.

Could it get any better? Actually, it could. The Rangitikei also happens to be famous for awesome hunting and fishing. Paradise. Having been picked up from Waipakihi road end along with an impressive pile of gear, we got everybody safely to camp by mid-afternoon with plenty of time to get a feel for the place. It looked steep, tiger country!

Jess Scrimgeour ecology technical advisor and Dave Conley partnership ranger setting up the first plot on a steep hillside.

Setting up the first plot on a steep hillside.

On day two we tackle the slopes to get the blood pumping, and the pressure is on, who will find the first snail? Two minutes in and Ian is first on the board, then Ed, then Jess. Eventually everyone was on the board except for me. Luckily I was on camera duty.

Lunchtime rolls around and I don’t think anyone was prepared for how much kai Ed and I could consume. The looks of astonishment throughout the following days were priceless – would we have enough food to get through the week after all?

Live snail and shells found in the first plot.

The numbers counted in that first plot were good

As the days passed we got stuck in, scratching away like chooks, surveying the plots line by line – some plots easier than others! Hot dry weather makes the going tough, as the leaf litter is hard and crisp, making for calloused fingertips. The never ending steepness of the infamous ‘line Z’ makes for calloused toes as well.

As the week progresses, Andi pulls ahead in the live snail count when she comes across a log harbouring a haven of powelliphanta. Dave briefly holds the lead for number of dead shells found, and gets labelled the grim reaper.

Despite all the bush lawyer and steep hills, it was a bittersweet feeling surveying the last plot, and the stakes increase with double points at stake. Andi ‘the snail whisperer’ takes out everything, topping both the live and dead snail counts.

While the trip was a great experience, our results were a little mixed. We found 120 live snails this year, which equates to a density of 3.4 live snails per 100 square metres. This is less than we found in 2009, where they found 151 live snails equating to a density of 4.2 live snails per 100 square metres.

Measuring a live snail.

As well as counting the snails the team also measured every snail located

Unfortunately we found a lot more shells than last time, which is not so good. Overall the proportion of shells predated by possums has not increased, so the management in place is still effective, and we found even fewer shells in the monitoring plots predated by birds this year (three) than last time (six).

Anecdotally we saw more shells surrounding anvil rocks (classic thrush behaviour) than ever before, so it is likely that their impact is growing. However, our data is suggesting that the majority of deaths came from natural causes. Maybe climate has something to do with it? Numerous ‘debriefs’ around the campfire at night didn’t shed any real light on the issue though!

Walking down Otamateanui after a day’s work in the hills.

Walking down Otamateanui after a day’s work in the hills

With the counting done, on our last night Ed and I head back to the tops one last time to chase a deer and camp for the night. Despite opportunities which made for a few hard luck stories, we end up empty handed. Meanwhile Dave hunts and fishes his way up the Rangitikei and rolls a stag over 10 minutes up from camp — go figure!

Helicopter at the Waipakihi Road end.

Eight people and all that gear to fit in that helicopter

Getting picked up from the Whakamarumaru tops was an awesome finish to the trip, a big thanks to Ian McNickle and the rest of the team that helped make it happen. It was a great opportunity to get in the back country for eight days with good company and work with Powelliphanta. I would go back in a heartbeat.