, WCS Canada
© WCS Canada

Building a wolverine trap


Related

Boreal Wolverines

Published

2021-06-21

How do you attach a collar to a wolverine?

Knowing basic information about a species is the first step to conserving them. How do you make management decisions about land use, resource harvesting or planning for infrastructure like roads if you don’t know where species of concern are, how they move, or how many of them there are in a given area? Technology such as acoustic transmitters in sturgeon or GPS collars on wolverines can be invaluable tools to help answer these questions.

But how do you attach a collar to a wolverine? These are highly elusive creatures that also happen to be very powerful. We need a way to capture these burly members of the weasel family in a way that is safe and low-stress for the animals and us.

When we live-capture wolverines, we are trying to fool the trickster, contain the wanderer, and learn the secrets of the elusive. This makes the live-trap itself a critical tool for wolverine research. The trap has to be safe for the wolverine, strong and durable enough to contain it, and clever enough to catch them. If any of these three features aren’t built into the trap, you won’t be catching a wolverine. I’ll explain how we build a trap to show what makes it safe, what makes it strong, and what makes it clever.

To start with, you can’t just hop into the woods and start building live traps for a threatened species. Wolverines are protected by the Species at Risk Act (2007), and the first step to studying them is to make sure we are working entirely within the law, while also respecting the wishes of the communities we are working in. We always work together with local governments (often Indigenous) and trappers to be sure everyone knows what we are doing and why. Local fur trappers are usually interested in conservation research and often help us pick a spot based on their knowledge of the area.

  • A level floor, and a pile of logs ready to assemble.

    A level floor, and a pile of logs ready to assemble.
    © WCS Canada

  • A second layer of logs makes the walls tall enough for the wolverine to move about inside.

    A second layer of logs makes the walls tall enough for the wolverine to move about inside.
    © WCS Canada

  • A heavy lid is fitted so it falls in place correctly.

    A heavy lid is fitted so it falls in place correctly.
    © WCS Canada

  • The custom-made trigger is a key part of the trap. The bait is attached to the wire which will pull the release lever on the vise-grip.

    The custom-made trigger is a key part of the trap. The bait is attached to the wire which will pull the release lever on the vise-grip.
    © WCS Canada

  • The trap is complete, now we wait for a wolverine to find it.

    The trap is complete, now we wait for a wolverine to find it.
    © WCS Canada

  • Wolverine M17 is taking advantage of an older lid which has dried and isn’t as heavy. The lock was also too loose, and he stayed around to play with the lid after escaping!

    Wolverine M17 is taking advantage of an older lid which has dried and isn’t as heavy. The lock was also too loose, and he stayed around to play with the lid after escaping!
    © WCS Canada

Once we get the spot settled, we go in with tools and get to work. It will take three people about 10 hours to build a trap, for a total of 30 person-hours for the initial construction. We start by felling a tree, it must be as big around as a dinner plate. We measure and cut the tree into lengths for walls. While one person is sawing, another person can level an area and begin to make the floor. To keep it from rotting, the whole trap is built on smaller logs that keep it up off the ground. These foundation logs need to be level so that later the lid hangs evenly. Large deck boards form a flat floor and are the only piece of store-bought wood we use.

Once the floor is done, we carry the large logs from the felled tree and organize them by size. As the tree tapers from bottom to top, the logs change size, so we need to stack them carefully to get walls that are even in height. The logs are notched so that the corners fit snugly. Usually two layers of logs will be tall enough so the wolverine has enough room to move about inside.

Next we need a lid. The lid is also notched at the ends so it can’t slide off forward or backward. It has to be quite heavy so it can’t be easily pushed open. Using wood that is green and full of water fulfills this requirement. When the trap ages over the summer it will dry out and the lid will become much lighter. Wolverines can then push the lid open, so we use a very clever propped stick to jam the lid closed. The lock must fit very precisely so it falls reliably into place each time the lid closes. Skip to Figure 6 to see what happens if the lock is not tight!

Keeping the heavy lid open and making the trigger mechanism is where we have to get clever. The trigger system is made of a cantilever combined with a vise-grip welded to a lag bolt. There is a beaver carcass attached to a wire inside the trap. When a wolverine pulls on the carcass, the wire tugs on the release lever on the vise grip and the jaws pop open, allowing the lid to fall.

Once the cantilever is made we can begin fine-tuning the trigger and the lock. You need everything to be tight and well-fitted so that the wolverine doesn’t get any ideas about potential weak spots. But at the same time, you also need the parts to move freely and reliably even when covered in snow.

Seeing the construction process reveals how we meet the three trap criteria: Safe, strong, and clever. The trap has a number of features that make it safe for the wolverine. The traps are very tightly fitted and no wind or snow can get inside, I haven’t seen a more cozy shelter from the weather in the woods than this – it is basically a custom-made wolverine log cabin. There is also no way any other animal can get inside, so should any wolves come by before we get there, there is no danger to the wolverine. Because the trap is about five feet long inside, the wolverine can’t possibly get caught under the falling lid, because it will be at the other end of the trap pulling the beaver carcass when the lid falls. This also means there is room for it to move around freely inside when the lid closes.

The strong construction, tightly fitted joints, and large logs all contribute to the strength of the trap. Wolverines regularly grind frozen moose bones into tiny shards for dinner and these same teeth can do some damage to comparatively soft wood. In fact, after a few years the logs become too soft, and we have to replace them as they begin to dry and warp with age. Constant trap maintenance keeps everything snug and tight and offers no options for wolverine escape.

I like to think the traps are pretty clever. We use what we know about wolverines to place traps in likely areas to catch them. We invent ways to catch them without causing harm and we use the animal’s characteristics to guide the construction of the trap. But as clever as we think we are, the trickster still outmatches us sometimes. When you show up to your trap and find a hole in the wall or the camera monitoring the trap reveals an epic escape it really makes you appreciate the strong will and character of these animals. Consider M17 in Figure 6 below, who decided to use our trap as a personal gym, doing power-squats with the lid.

The trap has some important and clever technology as well. Our traps are spread out over 6500 km2. Some traps are hundreds of kilometers away from each other. We need to know as fast as possible if a trap has an animal in it so we can get there and release it quickly. In Figures 5 and 6, you can see a satellite transmitter on the arch. These transmitters send us emails when the trap lid closes, so we spend all winter on-call watching our email, ready to rush out to a trap anytime, anywhere.

Our team is often spread out over the vast area our traps cover, but we always find a way to respond quickly when a trap is triggered, using satellite messengers to coordinate travel to the trap. Once our team members reach the trap, we will look who is inside by cracking open the lid just enough to see. If it is a wolverine who isn’t collared yet, we will carefully prepare some anaesthetic. It’s better for the animal not to perceive our handling and we are better able to fit the collar and care for a relaxed wolverine.

It takes two people to care for a wolverine asleep in the cold (we keep them wrapped in sleeping bags with hot water bottles during the assessment): one of us takes measurements and samples, while the other monitors temperature and vital signs using a thermometer, stopwatch, and stethoscope.

During the assessment, we pluck a bit of fur from the shoulders -- the follicle has DNA and the hair can be used to assess diet and stress levels. We also draw a blood sample from a front arm to measure various health indicators. Then we add a coloured ear tag so we can identify the animal in the future when the collar has dropped off as planned. Fitting the satellite tracking collar is the prime reason for undertaking all this trap building in the first place. Being able to see where our new friends go after they are released helps us understand a great deal about habitat use and behaviour in a vast and remote area. The collar can’t be too tight, nor too loose and we triple check that everything is operational before we give a reversal drug to wake up the wolverine.

At this point, we place it back in the trap where it will be sheltered and safe until it has fully woken up. When the wolverine has had time to wake up, we open the lid and watch the wolverine bound away (see video). But our work is still not done: We may also photograph the tracks it leaves behind to help with teaching others to accurately identify tracks of one of the northern forest’s most elusive animals, as scientist Matt Scrafford explains in this blog.

This process is a recipe for long days and long nights – often in frigid cold and deep snow -- for our field team. The wolverines keep us on our toes and we keep them on theirs. It’s a relationship I love and each time I approach a closed trap, I can’t wait to see who’s inside.

By Jacob Seguin

Wolverines

Wolverines

Wolverines are well adapted to live in northern environments where wilderness areas still exist.

Identifying key wolverine habitat

Identifying key wolverine habitat

We're surveying wolverine populations in northern Ontario to create a clearer picture of where wolverine are – and aren’t.