Timothée Bonnet bio photo

Timothée Bonnet

Evolutionary biologist/ecologist

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I have recently read that writers think scientists are not outdoor people. Well, that is clearly wrong, at least in the field of ecology and evolution. I would like to share with you what I did outside during my PhD, and why the fact that some scientists spend a good deal of time outside is a great thing.

Scree adventure

During my PhD, every summer I spent a few weeks on a scree slope in the Swiss Alps. Together with one or two colleagues, we would set about 120 traps on a corner of the scree in the afternoon (see picture above), all duly baited with apple and a dash of peanut butter, open them upon sunset, and leave for a short night at Churwalden village.

Before the crack of dawn, we would quickly swallow muesli in yogurt, and a bad coffee, without being hungry at all, but knowing that a long morning was ahead of us. We would run back on the top of our mountain armed with supermarket shopping bags reinforced with yellow duct tape (to collect traps), a notebook, a spring scale, calipers, a RFID-tag reader, cereal bars… We would open and collect the traps one-by-one and check if someone had snuck-in during the night. And there they would be… snow voles !

Each snow vole we ever captured has a unique identification number, and a small RFID-tag under their neck skin. When we capture a vole for the first time, we give it a name, a tag, and in exchange we take a tissue sample from which to extract DNA to confirm their identity and establish who are its parents. On every capture, we take a series of body measurement, look for signs of reproduction, and count external parasites. The voles are free to go after a few minutes.

You are guessing snow voles can’t be that interesting, why in hell would I do that?

You are right, we are not particularly interested in snow voles. I mean, they are cute and their lifestyle up in the mountain is pretty impressive. But they are biologically not that special, they have no socio-economic impact (they are not agricultural pests since they live in rocky habitats were livestock cannot graze), and they are not even threatened (which could justify some research on how to best manage them). It is really not about these snow voles, but about measuring things in a wild population; it could have been any wild population, this one just happened to be convenient to study: we can easily monitor the whole population because it is spatially well delimited, they are easy to catch, they reproduce fast, and the site is rather close to a human settlement. So, next logical question: why did we have to measure “things” in a wild population? Here it comes:

We know the environment of many species is changing more rapidly than ever in human memory. Biologists often recognize four ways in which wild populations can respond to these changes: they can genetically adapt, they can cope with changes plasticly (that is, they change directly in response to the environment, without genetic change), they can move to track their ideal conditions, or… sad face… they can die out.

On the long run, the best way for populations to persist is to genetically adapt. We know that evolution can sometimes happen sufficiently fast to rescue populations from extinction, there are some good examples, but in general we don’t know how likely rapid adaptive evolution is, and we don’t understand well how environmental changes translates into evolution.

How do we fix the ignorance of the human kind? By going to the field, collecting data in natural populations, and passing them through the sieve of the scientific method, statistics, muesli and bad coffee.

Hence me hopping like an ibex with an Ikea bag on the scree.

Also, it is nice to spend time in the Alps. You get to see tons of wild flowers, grouse, eagles, ibex, chamois, black salamanders, summer snow, deer bellowing in the middle of the night…

What we found

The snow vole population had been genetically evolving over the ten years of monitoring. In particular, they evolved to be lighter and shorter (these are two traits we could measure accurately, other unmeasured traits certainly evolved too). Evolution can be the result of different processes: immigration, mutations, random transmission of genes from parents to offspring (genetic drift), and natural selection (non-random differences in survival or reproduction). Natural selection is the main driver of adaptation, and is crucial for populations to respond to changes in their environment on the middle- and long-term. In this population, we were able to rule out immigration, mutations, and drift as important causes of evolution, leaving natural selection alone as the main driver of evolution. Moreover, we were able to link selective pressures to a major climatic fluctuation that affected the Alps during the 2000s. This snow vole population therefore provides one of the only documented example of current genetic evolution in response to climate. Finally, we showed that natural selection acted in this population in a way that was invisible to standard statistical methods developed for breeding and laboratory conditions. It is a bit technical, but in short, small-scale environmental variation (food abundance, parasitism…) affects both animal characters and their reproductive success, and thus masks the print of natural selection (which is the causal effect of the character on reproductive success).

Mathematical theories, computer simulations, and lab experiments are all great ways to learn things about our world. But often they give us a range of possibilities, rather than definitive information about how organisms work and evolve in nature. In the end, if we want to understand how organisms work in the outside world and predict their future, there is no way around spending time on the field and collecting basic natural history data.


Bonnet T, Wandeler P, Camenisch G, Postma E (2017) Bigger Is Fitter? Quantitative Genetic Decomposition of Selection Reveals an Adaptive Evolutionary Decline of Body Mass in a Wild Rodent Population. PLoS Biology 15(1): e1002592. doi:10.1371/journal.pbio.1002592 doi:10.1371/journal.pbio.1002592

Also a simplified version of the original article, written together with the team of the Science Journal for Kids: Are vole shrinking?.


Furry friend.