MSc project final presentation

During the lab meeting today Lauren gave a great final presentation today of her Masters project on the effects of the group personality composition on group learning ability in three-spined sticklebacks. Looking forward to her MSc thesis in a month’s time!


Invited seminar Glasgow University

jolle-seminar-glasgow-collectivebehaviour This week I visited Shaun Killen in Glasgow and gave a seminar at the Institute of Biodiversity, Animal Health and Comparative Medicine. Three stimulating days with lots of productive discussion and research ideas for collaboration on the relationship between physiology, personality differences and collective behaviour. Really great to meet the Killen lab and drink some proper Ales and Whiskeys. Thanks to Shaun for hosting me!

Learning a new skill: LaTeX

The last few weeks I delved into learning \LaTeX, a code language for more aesthetically pleasing article writing, especially in terms of mathematical formulas. As my research has increasingly been focused on the mechanisms underlying collective behaviour, for which I do a lot of mathematical computations, such an advanced yet simple text-editor is very helpful and overcomes the many pains I have with MS word!

(1)   \begin{equation*} v_i(t) = |\mathbf v_i(t)| = \sqrt{u_i^2(t)+w_i^2(t)}. \end{equation*}

(2)   \begin{equation*} \mathbf a_i(t)= \frac{\mathbf v_i(t+\Delta t) - \mathbf v_i(t)}{\Delta t} = \frac{\mathbf r_i(t+\Delta t) - \mathbf 2r_i(t)+\mathbf r_i(t-\Delta t)}{\Delta t^2}, \end{equation*}

(3)   \begin{equation*} \rho(t)=\frac{1}{n}\sqrt{\left( \sum_{i=1}^{n}\sin(\psi_i(t))\right)^2+\left( \sum_{i=1}^{n}\cos(\psi_i(t))\right)^2} \end{equation*}

It was quite a steep learning curve, but I managed to write my first paper with it last week. The great thing is that it is also possible to use \LaTeX in wordpress (which I used to create this website). It is also the standard language for drafting preprint articles, which is increasingly suggested and done in the biological sciences, thus a very relevant skill to learn.

Field trip in Catalunya

Observations of schooling Mediterranean barbel

Last week I was in Catalunya visiting friends and family and some undistracted paper writing. Catalunya, where my wife grew up, is an amazing place and feels like a second home to me. With the Mediterranean sea and the Pyrenean mountains within half an hour’s drive, there is always a lot to explore.

Hiking up the beautiful Gorge of Sadernes, Catalunya.

Hiking up the beautiful Gorge of Sadernes, Catalunya.

During some recent trips, I went hiking in the Pyrenean foothills and discovered schools of Mediterranean barbel (Barbus meridionalis). They seemed to be separate populations living in semi-isolated pools of a small mountain river. This species of Barbus is only native to a small area in and around the Eastern Pyrenees. Sadly, in recent years its numbers have plummeted with 30% (source: IUCN), highlighting an urgent need to better understand their ecology and vulnerabilities.

A shoal of Mediterranean barbel foraging on limestone rocks.

A shoal of Mediterranean barbel foraging on limestone rocks.

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Featured on German television

Yesterday our research at the Department of Collective Behaviour was featured in a half hour show on the German television: “Schwarmverhalten – Die Intelligenz der Vielen“. You can see the full program below or at this link. My postdoc supervisor Iain Couzin is featured from 01:18 and I make my appearance at 06:44.

Fische, Ameisen, Heuschrecken: Schwärme verhalten sich schlau, ohne, dass die einzelnen Tiere besonders intelligent sind. Der Schwarm ist die Intelligenz der Vielen. Können Menschen auch Schwarmverhalten nutzen – und Roboter?

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Camera calibration and reconstruction for fish experiments

The last few months I have been working hard on the sophisticated new experimental set-ups in the lab with which we will be able to get high spatial and temporal resolution tracking of large schools of fish, in tanks that are up to 3x3m in size!

To get highly accurate spatial data of the fish we need to correct for the distortion of the camera lens, which almost all lenses have to some extent. I just finished the script (in Python) that enables us to undistort the image from a camera using functions in opencv based on a video of a moving checkerboard.

Me calibrating a camera with a checkerboard pattern, with colours showing the output of my python script, with a school of 1000 moderlieschen in the background :)

Me calibrating a camera with a checkerboard pattern, with colours showing the output of my python script, with a school of 1000 moderlieschen in the background :)

It works pretty well already, even with non-optimal videos. Next step will be to stitch the videos of multiple linked camera’s.

Stickleback experiments with Schistocephalus

Recently I started a couple experiments related to parasite infection of Sticklebacks with Schistocephalus, a tapeworm with a fascinating life cycle that requires three separate host species. Our experiments focus on how the parasite affect the fish’s movements, its social interactions and positioning, collective behaviour, and survival in the context of predation.

Today, when moving fish around for experiments, I noticed one particularly bulged individual that, instead of a the smooth elongated body had the body shape of a brick! A clear sign of Schistocephalus infection. We put it down and measured its body weight, both before and after opening up its stomach cavity. What we found was not one, not two, not three, but four individual flatworms with a total weight of 55% of that of the fish! Incredibly how the fish could actually survive with such an immense parasite load.

Three-spined stickleback before and after removing four Schistocephalus worms

Three-spined stickleback before and after removing four Schistocephalus worms

New sticklebacks from the Bodensee

Went out again with the boat yesterday to catch sticklebacks. A cold but beautiful day. At first we couldn’t find them where I saw them last week, but soon enough it was clear they were still there but just very well camouflaged against the pebbled background!

With the three of us we managed to catch about 300 of them in half an hour by wading through the shallow waters. Most of the fish are likely 1st-years, but we also caught a couple older individuals that were huge, close to 10 cm!

After mooring the boat, we moved all fish to a large social housing tank at the Limnological institute where they will undergo a anti-parasite treatment for a couple weeks. After that I will move them to our fish lab at the University of Konstanz as well as to outside mesocosms. There they will ‘participate’ in a range of my behavioural experiments focused on individual differences in collective behaviour.

First boating trip on the Bodensee

The past summer, I successfully completed a motorboat course to enable me to drive a motorboat on the Bodensee, required for my ongoing research on fish collective behaviour. I got my “Sportbootführershein” in the post a couple weeks ago, and finally this weekend was able to ‘take the boat out’.


In the cold rainy weather of early November, I set-off with with a good friend on one of the motorboots from the Limnological Institute. The water was considerably clearer than during the summer, providing a visibility of just over 5 meters. It was beautiful being out on the water. However, in the first hour almost being out, we still hadn’t seen our first fish!


We navigated around the island of Mainau, and started exploring the very shallow areas near the mainland. I was a bit annoyed I hadn’t seen any fish yet, let alone any sticklebacks, but when we decided to cross under the bridge leading to Mainau we suddenly found thousands of them!

The water was so shallow that it was necessary to take the motor out, and continue by oars. But this also meant we could observe the swarming fish from very close. Despite sticklebacks being very abundant in the Bodensee, in the autumn and early winter most of them move to deeper waters, likely following the movements of their invertebrate prey. These remaining fish were apparently some of the last ones remaining in the shallows, likely seeking shelter in the shadow of bridge, and I was therefore very happy to have found them.

We spent about half an hour observing their movements and behaviour and I got some good ideas to come back for some more quantitative field measures of their group sizes and compositions. After that we decided to go for a quick snorkel before going back to the harbour.


With my freediving wetsuit, the 11 degrees C actually still felt very comfortable, and I was enjoying the relatively clear waters of the lake. The Bodensee has a very interesting geology, with relatively shallow water on its edges that can suddenly drop almost vertically tens and tens of meters into the deep.

We only snorkeled a bit above a drop-off near the harbour to check our wetsuits and the visisbility, which both passed our expectations. I therefore can’t wait to go back again and take the boat out the lake to catch wild individuals for my experiments, get some more quantitative observations of the sticklebacks and their predators, and explore underwater.

Submitted von Humboldt Fellowship

alexander-thumbToday I submitted a grant application for an Alexander von Humboldt Fellowship, entitled The ecological and evolutionary implications of individual differences in collective behaviour. The goal of the proposed project is to develop an interdisciplinary research program to investigate the link between consistent behavioural variation, the emergence of collective properties, group functioning, and ultimately individual fitness and between-group dynamics. I am very excited about this project and have started to lay the foundations for it here in Konstanz. Now 10 months wait ahead!