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Group dynamics and navigation in king penguin chicks (Aptenodytes patagonicus)

Final Report Summary - PENGUINAV (Group dynamics and navigation in king penguin chicks (Aptenodytes patagonicus))

How animals make decisions in groups and coordinate their movements when travelling together has recently emerged as a hotly debated topic in behavioural science. Yet in spite of a strong theoretical framework, empirical studies of group decision-making remain limited. Thus, one of the main aims of the PENGUINAV project is to provide much needed experimental work on animals navigating in their natural environment. We have suggested a new model system – king penguins (Aptenodytes patagonicus). These birds make excellent subjects since they have both a clear tendency to group and a strong motivation to return to a specific location within the colony. Chicks are of particular interest as they spend their first year of life in groups of other young, known as crèches.

The objectives of the PENGUINAV project were to investigate group navigation in king penguin chicks with an emphasis on decision-making processes by examining: 1) how the presence of experienced individuals affects navigational efficiency in group-mates and in the group as a whole; 2) mechanisms of conflict resolution in groups whose members have different preferred destinations; 3) how group size affects navigational efficiency; and 4) mechanisms underlying natural crèche movement.

To address our objectives we performed field experiments at Ratmanoff colony, Kergeulen Island on king penguin chicks, taking advantage of their strong motivation to return to their crèches if they are displaced. Chicks were displaced from their crèches and released in groups of different sizes and compositions. To monitor individual movements, each chick was equipped with a miniature GPS logger. We then performed detailed analyses of the resultant homing paths. In addition, experimental data were supplemented by field observations of natural crèche movements through a time-lapse photography system, MicObs, that was implemented for the first time for king penguin colonies.

The navigation of a group can be influenced heavily by differences in the individual experiences of its members. To address how experienced individuals change navigation of a group of king penguins, we experimentally created two types of pairs in which chicks differed in their level of navigational experience. Naïve pairs were composed of two chicks that had not been displaced before. Mixed pairs consisted of one naïve chick and one experienced chick that had a prior experience in navigating back to its crèche individually. Our results showed that naïve chicks homed faster and more efficiently if they walked together with their experienced partners compared to when they walked alone. Experienced chicks, however, maintained their relatively high walking speed and levels of efficiency irrespective of whether they walked alone or with others. Overall, pairs with an experienced chick travelled faster than naïve pairs. We also observed a shift in the leadership dynamics based on the experience differences. In naïve pairs, both chicks took turns in leading and following whereas, in mixed pairs, experienced chicks tended to take the leading position.

Conflict resolution
Conflicts may arise within a moving group if its members have different preferred destinations. We investigated the dynamics of decisions made by chick pairs navigating together to common or different destinations. To manipulate the levels of conflict faced by pairs experimentally, we captured individual chicks either at the same crèche (SC) or from two different crèches (DC). We displaced these pairs away from the colony and observed their homing. Consequently, SC pairs had no conflict over their desired destinations, while DC pairs experienced within-group conflict over their destinations. In both treatments, the majority of the chicks travelled at least part of the way together; and the closer partners were to each other, the further they walked together. A conflicting goal had a strong effect on group homing performance. The majority of chick pairs solved the navigational conflict by splitting. However, among DC pairs, we found no evidence that the size of the conflict affected the distance chicks would travel together. Chicks took turns in leading and following when walking together in both types of pairs. The need to navigate to two different destinations did not interfere with the chicks’ overall speed and efficiency. However, SC chicks arrived closer to their capture locations than DC chicks.

Group size
It has been previously suggested that navigational efficiency should increase with group size (the “many wrongs” principle). To address the question of how group size effects navigational performance in king penguins, we released groups of 1, 2, 6, and 10 chicks and observed their homing. When chicks travelled in pairs, they were more efficient and faster than individuals travelling alone. Groups of 6 and 10 individuals split into several subgroups of different sizes before chicks reached their crèches. Preliminary analysis has revealed that the number of interactions between individuals within groups of 6 and 10 remained the same, suggesting that there is an optimal operational group size. We are currently investigating further the navigational performance of larger groups.

Crèche movements
In addition to experimental manipulations, we have also monitored natural colony movements through a recently developed time-lapse photography system, MicObs. Preliminary analysis of these data has revealed that king penguin chicks’ distribution in the colony can undergo three different turnover regimes. The first is the predator attack regime, observed when chicks are suddenly driven away from their location in the colony by a predator, to which they return after ~20 min. The second is the microclimate induced turnover regime, where chicks remain up to 3 hours in the same place, and move only because of environmental changes (e.g. temperature, wind, rain). The third, unknown regime, lasts over 3 hours and probably accounts for wandering chicks that join crèches for the night. We are continuing our data analysis further.

This has been the first study that investigated group navigation in king penguins, thereby broadening our knowledge of king penguin biology and providing valuable empirical tests for theoretical models of leadership and information transfer within animal groups. The obtained results support some, but not all, theoretical predictions, suggesting that the generality of existing models needs to be re-evaluated and additional parameters may need to be considered in order to increase their applicability.

The success of the project was based on collaborations between several EU labs (UK, France, Germany), and a number of new collaborations (Netherlands, Germany, Hungary) have been established in the course of the project. These collaborations have enhanced European excellence in the exciting and thriving field of group navigation and stimulated information transfer across the European scientific community. Moreover, the project provides an example of how animal colonies can be monitored non-invasively via the MicrObs system, a new technological advancement, with the possibility to address questions at the individual, group, or colony levels. This methodology could be implemented for conservation purposes and for data collection in remote or hard-to-access places where continuous presence of human observers is not practical or possible.