We Set Up Boxes in the Forest for Pine Martens
By James McConnell, Technical Director
I’ve never set up a pine marten den box before.
I’ve set up countless camera traps, especially on the North York Moors, looking specifically for pine martens. I’ve also set up bait stations, 4G cameras, hair tubes and more.
I’ve seen lots of den boxes already on trees and listened to expert advice in the forest about suitable locations and box types.
But - I’d not actually been there when one got hoisted up a tree, to ideally become a refuge for a rare carnivore that has been central to my professional life for the last 13 years.
So this summer, I couldn’t miss the opportunity to be there as new boxes were raised aloft, adding to the 30+ den boxes already out there.
The boxes are going up as part of a new phase of work on the North York Moors that NatureSpy has been deeply involved with since 2011 - the NE Yorkshire Pine Marten Pathways Project.
This is a new partnership of Forestry England, NatureSpy and Yorkshire Wildlife Trust. The project aims to set the future direction for pine marten recovery in Yorkshire.
I met up with our Conservation Manager Ed, who himself has worked with pine marten in Yorkshire for over 8 years, and Yorkshire Wildlife Trust’s Species Recovery Officer Luke, on a sunny day to get cracking.
When I arrived, they were already getting the gear together - and it’s a lot of gear. Putting up a pine marten den box is very different to putting up a birdbox.
The boxes themselves (depending on the type) can weigh up to 15kgs. They need to go about 2-3m up a tree - which means ladders, harnesses, pulleys, and lots of safety equipment and considerations.
For Ed and Luke, this is already a well-oiled machine - the prep done in the run up to today means that Ed already has mapped out and pre-approved locations where the boxes are going up. It’s the culmination of a lot of desk-based work.
I get given one of the smaller boxes, Luke takes one of the bigger ones and Ed takes the collapsible ladders, harnesses, and cameras. Everything is heavy.
Ed signals that we need to head into the trees. We dive into the thick stands of pine, with spikey branches at every level. When you're carrying the gear, this is even harder to walk in - trying to dodge boggy pools and eye-gauging branches at the same time, with no hands to push anything out of the way.
We get to the rough area and everyone eagerly downs the kit onto the spongy, pine-needle- covered forest floor. Straight away their eyes start to scan the immediate surroundings, and Luke and Ed start pointing, discussing and pushing on certain trees, to see how much they move.
They're looking for a tree which must be suitable for the box. It can’t be any old tree.
We’re looking for the goldilocks tree - straight (obviously…), not too crowded, thick enough so they won’t wave too much in the wind and are strong enough to hold the box, not too thick that we can’t get the rope around, with some sturdy branch ends at just the right height to hook the box’s rope around.
It also needs a crucial natural pine marten ladder - old branches fairly low down that the martens can use to climb up to the box more easily. On den boxes that were set up in a previous project phase which were used by martens, you can see their claw marks on these lower branches.
Added to that, it needs a partner tree - one that is close, but not too close, where we can setup a trail camera with a good view of the den box entry points.
A consensus is reached. Ladder unfolded. A special harness goes around this and the tree, locking the ladder in place so it cannot move.
Ed dons his own harness, clipped in around the tree so he can work securely and hands-free. His ladder training, which he did specifically for this work, has kicked in.
The pulley is then set up - one end of rope gets attached to the den box, and Luke holds the other end. Once Ed gives the all clear, Luke walks away from the tree and the den box effortlessly floats up.
It’s cajoled into a sturdy, level spot and Ed secures it in place. Branches around the box are trimmed to make space for the box, so it can sit firmly and not rock in the wind.
The final part is back down the human ladder - getting a pine marten ladder ready for the species we hope will head up this tree and into the box soon. Ed gets to work sorting the ideal climb for any visiting pine marten.
The den box itself can now stay here for about 3-5 years, until a revisit is needed to loosen the rope around the tree that secures the box as the tree grows and expands and and refresh the bedding inside.
The corresponding camera is set up and then it’s off to the next location.
The den boxes are going up in plantation forests - which is what the vast majority of forest on the North York Moors is. There are not many mature deciduous trees that have natural denning holes inside, or craggy, steep cliffs where martens can find refuge.
When in these plantation forests, you can see why the den boxes are needed. There is nowhere else for a pine marten to rest, retreat, hide, or even breed. If the pine marten that are already finding their way to these forests are going to stand a chance, den boxes are a crucial part of their future.
It takes the best part of a day to get 5 den boxes out, and it’s hard work. But it’s not just wooden boxes on trees - these are meticulously designed boxes that take a lot of time, effort and expense to get to their hopeful end purpose - a 2-foot-long mustelid, quietly clambering inside.
We hope that will happen soon with these new boxes - but the below videos are an example of what we've previously captured in the project area. The first clip is a marten circling on top of a den box, before marking it - typical marten behaviour.
The second is what we never tire of seeing - a marten going back inside for a kip!
