New paper out in ProcB!

From swarm to school, stickleback groups differ repeatedly in their collective performance  

 among schooling fish, groups can have different collective personalities, with some shoals sticking closer together, being better coordinated, and showing clearer leadership than others.

For centuries, scientists and non-scientists alike have been fascinated by the beautiful and often complex collective behaviour of animal groups, such as the highly synchronised movements of flocks of birds and schools of fish. Often, those spectacular collective patterns emerge from individual group members using simple rules in their interactions, without requiring global knowledge of their group.

In recent years it has also become apparent that, across the animal kingdom, individual animals often differ considerably and consistently in their behaviour, with some individuals being bolder, more active, or more social than others.

New research conducted at the University of Cambridge’s Department of Zoology suggests that observations of different groups of schooling fish could provide important insights into how the make-up of groups can drive collective behaviour and performance.

In the study, published today in the journal Proceedings of the Royal Society B, the researchers created random groups of wild-caught stickleback fish and subjected them repeatedly to a range of environments that included open spaces, plant cover, and patches of food.

“By filming the schooling fish from above and tracking the groups’ movements in detail, we found that the randomly composed shoals showed profound differences in their collective behaviour that persisted across different ecological contexts. Some groups were consistently faster, better coordinated, more cohesive, and showed clearer leadership structure than others.

“That such differences existed among the groups is remarkable as individuals were randomly grouped with others that were of similar age and size and with which they had very limited previous social contact.”

This research shows for the first time that, even among animals where group membership changes frequently over time and individuals are not very strongly related to each other, such as schooling fish or flocking birds, stable differences can emerge in the collective performance of animal groups.

Such behavioural variability among groups may directly affect the survival and reproductive success of the individuals within them and influence how they associate with one another. Ultimately these findings may therefore help understand the selective pressures that have shaped social behaviour.

Dr Andrea Manica, co-author of the paper, added: “Our research reveals that the collective performance of groups is strongly driven by their composition, suggesting that consistent behavioural differences among groups could be a widespread phenomenon in animal societies”.

 These research findings provide important new insights that may help explain and predict the performance of social groups, which could be beneficial in building human teams or constructing automated robot swarms.

The study is published in the 7 February 2018 issue of Proceedings of the Royal Society B and is available Open Access: http://dx.doi.org/10.1098/rspb.2017.2629

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New paper out in Current Biology!

My latest paper on the collective behaviour of stickleback shoals is out today in the journal Current Biology!

Jolles, JW, Boogert, NJ, Sridhar, VH, Couzin, ID, Manica, A. (2017) Consistent individual differences drive collective behaviour and group functioning of schooling fish. Current Biology 27: 1-7. doi: 10.1016/j.cub.2017.08.004 (link).

Highly coordinated school of three-spined sticklebacks swimming in the blue waters of the Bodensee near Konstanz, Southern Germany. Photo: Jolle W. Jolles

Highly coordinated school of three-spined sticklebacks swimming in the blue waters of the Bodensee near Konstanz, Southern Germany. Photo: Jolle W. Jolles

New research sheds light on how “animal personalities” – inter-individual differences in animal behaviour – can drive the collective behaviour and functioning of animal groups such as schools of fish, including their cohesion, leadership, movement dynamics, and group performance. These research findings from the University of Konstanz, the Max Planck Institute of Ornithology and the University of Cambridge provide important new insights that could help explain and predict the emergence of complex collective behavioural patterns across social and ecological scales, with implications for conservation and fisheries and potentially creating bio-inspired robot swarms. It may even help us understand human society and team performance. The study is published in the 7 September 2017 issue of Current Biology.

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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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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’.

driving-the-motor-boat

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!

view-over-the-lake

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-wetsuit-on-the-boat

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.

Wild schools of Moderlieschen

Last weekend I went exploring the streams and lakes in the countryside near Konstanz to search for Moderlischen and determine the possibilities for doing fieldwork to investigate group movement dynamics and composition in the wild.

I was able to find them in some tiny streams leading to a small lake, showcasing some nice examples of collective shelter use and leadership and exploration of the stream, see the video below. Looking forward to starting exploring possibilities to start some actual field work on these populations.

New stickleback in the lab

For my new research projects on the role of individuality in collective movements and decision making at the University of Konstanz, I have been getting new sticklebacks from the Bodensee. Last weekend I went to see them together with my 10mo son! I think it was the first time he actually ever saw moving fish. Although I showed him fish in aquaria before, he was too young to react to them, but this time he was amazed by the large school of fish swimming back and forth. The sticklebacks from the lake were absolutely huge, I estimate up to about 9cm, much bigger than the ones I ever saw in Cambridge and the ones in the ponds near the University here. I hope to go on a trip soon to observe the collective behaviour of the sticklebacks in lake Konstanz, the ponds, and streams in the area to set-up some exciting experiments on the population-specific differences of this amazing species.

Here I am showing my son a school of Moderlieschen

Here showing my excited son a school of Moderlieschen

Short visual on vectorized movements of small fish school

My research is currently centred around understanding the role of consistent behavioural differences in the collective movements and functioning of animal groups. In particular, I assay large numbers of stickleback fish on various personality traits and expose them in groups to different ecological scenario’s. I have written custom tracking software in Python using the OpenCV library to be able to accurately track the position of individual fish in the freely-moving schools.

Today I wanted to share a simple visual that highlights the detailed individual-based tracking of a small fish school over time. Each fish is represented by a different colour, with the arrow showing its vectorized movement, with larger arrows indicating a higher speed. The video is centred around the vector of the group as a whole to better visualize the structure of the group over time. Lines indicate the smallest polygon encompassing all individuals and Individual Centre Distances. The moving axes indicate the relative speed of the group in a large circular arena.

In this short section of a 30-min long experimental trial it is clear that the group speed, cohesion, and structure fluctuate over time. At the same time, individuals also maintain to some extent their positions relative to the group centre, such as the green and yellow individual clearly having a stronger pulling power on the movements of the group as a whole.

I used RaspberryPi computers to film the fish, custom Python tracking scripts to acquire individual X,Y coordinates for each individual in the group, R to process the tracking data and acquire movement characteristics, and R with ffmpeg to create the visual.

Drawing sticklebacks

I have been trying to improve my drawing skills to better illustrate how my sticklebacks behave and in what way personalities matter in collective behaviour. I still have a far way to go but this is my latest quick sketch that shows four sticklebacks with different morphologies. When I get more time on my hands after I hand in I will try to get some more elaborate drawings done!

stickleback-drawing

Almost there..

Just over three years ago I was standing up to my waist in cold water, somewhere in the vicinity of Cambridge. I was catching sticklebacks for the first experiments of my PhD. Now, 37 months later, I am in the final stages of writing-up and will actually hand in my thesis in ten days time! During this last chapter of my PhD, I have also become a dad and am actually writing this with my 5 month-old son in the carrier on my chest. Luckily, after a nice walk with our dog in the cold autumn air, he has fallen vast asleep.

IMG_1828

If it wasn’t for all funding falling away at the 3 year mark, one and a half month ago, I would be continuing with some additional exciting data chapters of which I already got the data. However, with five data chapters, two of which are published and two have been accepted, I have enough exciting work to talk about. In the months to come, I will be wrapping up a lot of small and large stickleback projects that I have done over the years and that have not made it into my thesis, besides some nice collaborative studies, and will continue with further experiments on the link between personality and collective behaviour as a Postdoc!

Now, time to get back to thesis writing..

Stickleback spine-use project

Very recently two part IB students of mine finished a nice little experiment on the spine-use of three-spine sticklebacks. We were interested to see how personality might be related to the raising of the spines of three-spine sticklebacks as it helps them in protection against predators. Watch this close-up video that I took that nicely shows one individual stickleback raising its spines and lowering them again after feeling threatened by my presence. Hopefully soon we have the manuscript out with the findings of our study!

Last experimental work of PhD finished!

stickleback-testing-JollesToday I finished my last experiment that will be part of my PhD! I have been locked away in the lab for a couple weeks, testing hundreds of fish on their personality and collective behaviour, but now analysis and writing can fully start. I must have tested close to a thousand fish in the two and a half year since the start of my PhD, most of which are now enjoying a happy end of their lives back in the wild. I have all the data of a number of exciting projects that will not need me to go back to the lab for at least half a year but I can actually not wait to test my next hypothesis! The three-spine stickleback is an amazing species to work with and I will definitely continue working with them after my PhD.

Bold fish are less sociable and thereby affect leadership and group coordination

Recent research of colleagues and I at the University of Cambridge has revealed that sticklebacks with bolder personalities are not only better leaders but also less sociable than more timid fish. The behaviour of these bolder fish shapes the dynamics of the group.

See a 4min video about our research here http://youtu.be/5TSim9TkXiwSee a 4min video about the paper here: http://youtu.be/5TSim9TkXiw

Throughout the animal kingdom, individuals often live and move together in groups, from swarms of insects to troops of primates. Individual animals may benefit from being part of groups, which provide protection from predators and help in finding food. To ensure that individuals reap the benefits of togetherness, group members coordinate their behaviour. As a result, leaders and followers emerge.

Within groups, animals differ from each other in how they cope with their environment and often exhibit distinctive traits, such as boldness or sociability. Even three-spined sticklebacks, the ‘tiddlers’ collected from streams and ponds by generations of schoolchildren, can be described in terms of their personalities: some are bolder and take more risks, while others are more timid and spend more of their time hiding in the weeds.

Research carried out in the Zoology Department at the University of Cambridge suggests that observations of these tiny fish, and how they interact with one another, could provide important insights into the dynamics of social groups, including humans.

Jolle Jolles, lead author of the study, said: “Although we now know that the spectacular collective behaviours we find throughout the animal kingdom can often be explained by individuals following simple rules, little is known about how this may be affected by the personality types that exist within the group.

Experimental design. Fish were tested twice for one hour in the risk-taking task during two subsequent sessions. During the pairing session fish could see and interact with one another through a transparent partition.

Experimental design. Fish were tested twice for one hour in the risk-taking task during two subsequent sessions. During the pairing session fish could see and interact with one another through a transparent partition.

“Our research shows that personality plays an important role in collective behaviour and that boldness and sociability may have significant, and complementary, effects on the functioning of the group.”

In the study, the researchers studied the behaviours of sticklebacks in tanks containing gravel and weed to imitate patches of a riverbed. The tanks were divided into two lanes by transparent partitions and randomly-selected pairs of fish were placed one in each lane. Separated by the see-through division, the fish were able to see and interact with one another.

stickleback-tracking-perosnality

The positions and movements of the individual sticklebacks were recorded using sophisticated tracking technology, enabling accurate comparisons to be made of each fish’s role in the collective movement of the pair.

“We found that individuals differed considerably and consistently in their tendency to approach their partner,” said Jolles. The study showed that more sociable individuals tended to be coordinated in their behaviour while less sociable individuals were more inclined to lead.

Dr Andrea Manica, reader at the Department of Zoology and co-author of the paper, added: “Our research revealed that the tendency of fish to approach their partner was strongly linked to their boldness: bolder fish were less sociable than their more timid group mates.”

Jolles explains that sociability may form part of a broader behavioural syndrome. “Our results suggest that bolder, less sociable individuals may often lead simply because they are less reluctant to move away from their partners, whereas shyer, more sociable, individuals become followers because they prioritise staying close to others,” he said.

fig1

“Differences in boldness and sociability may be expressions of underlying risk-prone or risk-averse behavioural types, as risk-averse individuals may be more motivated to group together and to respond to other individuals in order to avoid predation.”

The findings of this study suggest that leadership and group coordination can be strongly affected by personality differences in the group and that boldness and sociability may play important but complementary roles in collective behaviour.

Jolles added: “Now we know these personality traits affect the collective movements of pairs of fish, the next step is to understand their role in the functioning and success of larger, more dynamic groups.”

See a 4min video in which we explain our paper in more detail below:

jolles-animal-behaviour-stickleback-leadershipClick here to download the paper.

Jolles JW, et al. (2015) The role of social attraction and its link with boldness in the collective movements of three-spined sticklebacks. Animal Behaviour, published online 2 Dec. Doi: 10.1016/j.anbehav.2014.11.004

Leadership in fish affected by previous experiences and linked to personality

Leadership behaviour is affected by social experiences from previous partners and depends on an individual’s personality, as shown by our latest study with three-spined stickleback fish, now published in Behavioral Ecology.

sticklebacks

From the political affairs we see on the news, to making decisions with your friends, leadership is all around us. But next to humans, leaders and followers can also be found in many group-living animals, such as fish, birds, and primates.

Social animals may receive benefits from grouping such as protection from predators and help in finding food. But to ensure individuals reap the benefits of grouping, they must time and coordinate their behaviour with the emergence of potential leaders and followers as a result.
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Timelapse video of a boldness session

Continuing on from yesterday’s post about the personality testing for boldness, today I made a time-lapse video from one of the sessions to get a quick overview of the actual running of the experiment. For most experiments I work with 40-64 fish per batch and potentially run multiple batches. Therefore, to be able to test all fish on the same day I test 8 fish simultaneously in 8 separate lanes for one hour and run 8 consecutive sessions in a row.
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Testing boldness in three-spined sticklebacks today

Throughout the animal kingdom, individuals have been found to behave consistently different from one another over time or across different contexts. This is now mostly referred to as “animal personality”. As part of my PhD I want to understand what role such personality traits play in the structuring and functioning of social groups, i.e. in collective behaviour.

Today I am running an experiment to investigate the consistency of risk-taking behaviour, also known as the boldness personality trait. I work with three-spined sticklebacks that I caught in wild streams near Cambridge. The three-spined stickleback is a wonderful little fish that is not only easy to work with and keep in the lab but a model system for collective behaviour and animal personality.

Topview of the boldness tank with left the deep covered area that leads to an increasingly shallow area on the other side. You can see a fish and its trajectory in the toplane

Topview of the boldness tank with left the deep covered area that leads to an increasingly shallow area on the other side. You can see a fish and its trajectory in the toplane

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Just another (cold, 12 hour) day in the lab

Often I wear a thick winter coat when working in my lab but today I forgot it.. Just on a day when I have to spent 12 hours in the lab..

Often I wear a thick winter coat when working in my lab but today I forgot it.. Just on a day when I have to spent 12 hours in the lab..

Although most people will probably be enjoying another warm and sunny summer day (unless you live in Britain), I will be in my underground fish lab for 12 consecutive hours. It is about 11 degrees Celsius down here to keep the water housing the hundreds of sticklebacks nice and cool so they won’t get into breeding state and show the associated changes in territorial/mating behaviour. I am however feeling a bit chilly as well as I forgot my coat today.. By typing this I hope at least my hands and fingers will warm-up a bit.

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