Behind the Spy: camera trapping under the snow

By Kat Holmes

Eeva Soininen is a researcher working to understand the species interactions that take place within food webs in the arctic tundra habitat. She works in seriously cold conditions and recently developed an amazing way to camera trap wildlife under the snow! I was lucky enough to speak to her and find out more.

These are likely to be grey-sided voles (Myodes rufocanus) interacting in the tunnel. Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT - The Arctic University of Norway.

[KH]  Thank you for agreeing to talk to me Eeva - it is very exciting to talk to someone working in such a different environment. Where exactly are you based and what is it like to work there?

[ES] I live in Northern Norway, in the city of Tromsø about 500km north of the polar circle. We have snow on the ground and below-zero temperatures for about half of the year. All of the life here has to adapt to that, meaning that all small mammals are living the winter part of the year in tunnels under the snow. For someone who is working with small mammals it means that for a great part of the year their life is quite inaccessible.

[KH] Had you used camera traps before and do you remember the first time you used one?

[ES] Not in my own research. This is the first time I have really worked with camera traps, so I remember very well when we put out the first traps two years ago. That was very exciting and of course we could not wait very long before checking if they worked. That was in the autumn, before the snow came, and we captured voles and shrews as expected. W also something we did not expect: insects and birds that had entered the traps to feed on the insects.

Great tit entering the camera trap tunnel to feed on insects

Great tit entering the camera trap tunnel to feed on insects. Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT - The Arctic University of Norway.

[KH] Camera traps are so great for finding out wildlife secrets but you have taken that a step further; how did you come up with the idea and design for your under the snow cam?

[ES] I have to give credit for the original vision to the other members of the development team. We were after a trap that would be better for capturing the Norwegian lemmings. It was after we started the development we realised that an automatic camera trap, unlike other traps, could also be used under the snow throughout the winter.

[KH] So how does it work?

[ES] It is basically a box with a camera attached in the ceiling, so that it is aimed downwards. The box has a hole in each end, forming sort of a tunnel. Because small mammals like tunnels they enter this artificial tunnel readily. When they enter they are noticed by the movement sensor of the camera and a picture is taken. We basically put the box along a rodent runway, so that it became incorporated into their environment; a little like if someone constructed a bridge over a road.

[KH] What are you using your chilly under the snow camera trap to find out?

[ES] We hope to look at many very basic things that remain unknown about the winter ecology of small mammals – because it has been so difficult to get hold of what happens under the snow. One big question is the winter crashes of small rodent populations. Arctic rodents have cyclic population fluctuations; every four to five years they are extremely abundant and then they disappear. As the population crashes often happen in winter we know very little about them, and both predators and poor snow conditions can in principle cause them.

A common shrew, just one of the small mammals Eeva is studying.

A common shrew, just one of the small mammals Eeva is studying. Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT -The Arctic University of Norway.

[KH] Lots of discoveries to make then. Your work must be very important to see the impacts of climate change on the Arctic habitat, is that right?

[ES] Well, I definitely hope to contribute. Mild weather and rain during the snow cover season can lead to the development of an ice layer on the ground, which prevents small rodents from feeding (the species I work with feed on plants). With climate change we are getting more and more mild winters. This probably means more difficult winters for small rodents and because of that less regular high rodent densities. As rodents are the main food for many arctic predators the consequences of mild winters can escalate through the whole arctic food web.

A stoat (Mustela erminea), one of the predators of small mammals in the arctic.

A stoat (Mustela erminea), one of the predators of small mammals in the arctic. Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT - The Arctic University of Norway.

[KH] It sounds like you will make an important contribution. What has been your favourite camera trap result so far?

[ES] It is always nice to see some social behavior. Also photos of the rodent predators are quite cool to look at.

A least weasel (Mustela nivalis) visits the camera trap, another arctic predator species.

A least weasel (Mustela nivalis) visits the camera trap, another arctic predator species. Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT - The Arctic University of Norway.

[KH] What wonderful captures you have made which reveal the secretive Arctic wildlife. I am afraid we always ask people the same question next… what has been your biggest camera trap fail or challenging moment?

[ES] Hmm… It would be the unsuccessful placing of some camera traps so they got badly flooded during the snow melt spring.

[KH] Wow that is quite some fail! Do you have a top tip for camera trappers out there?

[ES] Be patient! To use a below snow camera you need to install the camera before the snow comes – and then wait until the snow is gone before you get any photos. If you dig out the camera mid-winter you may disturb the runways of small mammals and it could happen that they do not like to enter the trap anymore. Careful placement is also important – you do not want your trap to swim in the meltwater when the snow melts…

These three grey-sided voles (Myodes rufocanus) are huddling for warmth under the snow.

These three grey-sided voles (Myodes rufocanus) are huddling for warmth, a critical behaviour when you live in the Arctic! Photo courtesy of Climate-Ecological Observatory for Arctic Tundra / UiT - The Arctic University of Norway.

[KH] Thanks, patience is so important! One more question… what’s your number one camera trapping goal for the year?

[ES] That would be finding out in what kind of places the Norwegian lemmings spend their winters. They are the most intriguing small rodents we have here – seemingly absent for several years and all in a sudden everywhere.

[KH] Sounds fascinating, will you keep us up to date on how you get on?

[ES] You can keep updated here (in Norwegian) or here (in English).

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