Tree Climbing and Rimu Fruit

 

 

In March we had teams head out to both Anchor and Whenua Hou to climb trees. While this may sound more like an activity suited to kids, its actually a really important part of our management. We carefully monitor the levels of fruit growing on rimu trees on both islands as masting (mass fruiting) of rimu is a known trigger for kākāpō to breed.

 

Why do you climb trees?

The climbers work in teams of two and scale a carefully selected set of rimu trees across both of the islands in order to count the green fruit present on the tips. By calculating the percentage of tips that are carrying fruit this will give us a good indication of how much fruit there will be and how likely there is to be breeding during the next summer.

A rimu branch, showing two fruiting tips

A rimu branch, showing two fruiting tips

There’s always a lot to do during a breeding season, so the more warning we can get, the better! During a breeding season the team expands significantly as we use more rangers on the islands, employ vets to provide technical assistance and also have hundreds of volunteers assisting us over the summer and following months. Our focus also shifts from research and long term plans and improvements to improving fertility, getting eggs to hatch and as many chicks as possible to fledge.

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Jason counts fruiting tips

 

What level of fruiting is needed?

Weather patterns and tree climbing allow us to predict if there is an upcoming breeding season and also how big it is likely to be. For kākāpō to breed the trees must have a minimum of 10% fruiting tips. Less than this and there won’t be any breeding. In bumper years the fruit will increase up to about 30-40%. These levels will trigger most females to breed, while levels closer to 10% will only trigger some of the females.

 

The 2017 results

Jason and Maddie van de Wetering headed down to Whenua Hou to count the fruit there for us. Wind and rain meant it took them longer than usual to complete the work, as trying to count tiny growths on the tips of branches is no fun when you’re being tossed around like a ship in a storm! They got the job done in between the worst of the weather and reported a tiny 0.5% of the tips had fruit.
Previous scientist for the team Ron Moorhouse made a guest appearance on Anchor Island to complete the fruit counting there, along with ranger Theo Thompson. Again the result was very low, with only 0.61% of tips fruiting.

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Climbing a rimu tree

 

 

These results mean that there will definitely be no kākāpō breeding on Whenua Hou and Anchor Island during 2018. But we aren’t sure yet whether breeding will occur on Little Barrier Island, which doesn’t have rimu trees and the kākāpō there have different triggers. Weather patterns are looking good for a potential rimu mast the year after in 2019, so the southern islands will just have to wait until then.
While this is a sad result, no breeding next year in the south will also give us a chance to plan and organise. With a new team structure coming in and kākāpō population growth meaning that we’re planning for new sites there’s plenty to do in the mean time without baby kākāpō to manage.

 

All photos taken by Maddie van de Wetering