Stickleback Leaders are Stickleback Loners

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 behavior. 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. The findings are published in Animal Behavior.

 

“Although we now know that the spectacular collective behaviors 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," said Jolle Jolles, lead author of the study. “Our research shows that personality plays an important role in collective behavior and that boldness and sociability may have significant, and complementary, effects on the functioning of the group.”

 

In the study, the researchers studied the behaviors 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.

 

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 behavior 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 behavioral 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 priorities staying close to others,” he said. “Differences in boldness and sociability may be expressions of underlying risk-prone or risk-averse behavioral 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 behavior.

 

“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,” said Jolles. "Although our study was conducted with fish and its results are therefore not directly applicable to humans, it provides new insights into the mechanisms that underlie group behavior and may therefore even tell us something about ourselves.”

 

Source: University of Cambridge