A recently published long-term study has been carried out in the Shark Reef Marine Reserve in Fiji which has discovered that bull sharks have stable social connections, that they show preferences towards particular companions instead of associating with anyone randomly, which supports the old view of sharks as highly individualistic creatures.
The study conducted by the scientists at the University of Exeter, Lancaster University, Fiji Shark Lab and Beqa Adventure Divers monitored the behaviour of 184 bull sharks during six years. The analysis of people at three stages of life has been made sub-adults, adults and older, post-reproductive sharks, which provides one of the most comprehensive insights to date on shark social structure.
The researchers claim that the sharks showed what they refer to as active social preferences and the sharks often associate with specific individuals and shun certain individuals. These relationships were assessed using proximity of sharks which swam within one body length of one another and more complex relationships like parallel swimming and the pattern of the leader-follower movements.
According to lead researcher Natasha D. Marosi, the results indicate that there are similarities between the results and social behaviour in humans and other animals whereby people do not interact randomly but instead have a range of relationships.
In the study, the adult sharks constituted the center of these social networks and the most common and close interaction were among the sharks of the same size. Conversely, younger sub-adults and older sharks were not as socially bound meaning that there might be differences in social activity among life stages.
Males Prefer Larger Number of Social Contacts
It was also found by the researchers that both male and female sharks preferred associating with females. Nevertheless, males were determined to have a larger number of social contacts in general. The study hypothesizes one possible reason, which is that larger male sharks can reduce the threats of aggression by other large sharks through heightened social integration.
Professor Darren Croft of the University of Exeter stated that the research evidence suggests the degree of behavioural sophistication which is not normally associated with sharks, indicating that sociality can confer benefits such as foraging success, learning and mating opportunities and avoiding conflict.
The Shark Reef Marine Reserve, which is an enclosed zone where sharks flock throughout the year allowed tracking the same species over a period of time. This consistency enabled scholars to examine how social associations were changed with the passage of time as the sharks grew old.
The paper also emphasized the fact that younger sharks are more likely to be found in other habitats including nearshore, rivers and estuaries where evading predators, including adult bull sharks is their main survival strategy. Few sub-adults were seen coming into the reserve with some seemingly being able to establish relationships with older sharks, which could have helped them integrate and learn.
In the old sharks, however, the researcher found them to be less active socially, which they theorize might indicate a certain level of experience in hunting and survival, and therefore, experience no necessity of social interaction.
Researchers say that the findings may be used in conservation efforts. The improved knowledge of shark socialization can be used to inform the management policy, especially in the protection zones where human activity and ecotourism overlap with the marine ecosystems.
Fiji Shark Lab is currently collaborating with Fiji Ministry of Fisheries to integrate the behavioural perspectives of the study into the conservation process since scientists keep on trying to understand the social lifestyle of shark species, which have been severely misinterpreted over a long period of time.
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