Buddies in the Sea
- 1 day ago
- 2 min read
The Social Life of Bull Sharks Is More Complex Than You Think
Fin to fin, these two bull sharks glide through the water: In front swims the powerful "Chunky," closely followed by the younger "Lady Lazarus." The two predators are apparently not just members of their own species, but something like friends. For a long time, sharks were considered solitary hunters and loners without social bonds. But new observations show that they repeatedly seek out certain members of their species.
As coastal inhabitants, bull sharks (Carcharhinus leucas) are found in tropical and subtropical waters worldwide. They can live in both salt and fresh waters and often dive far up rivers. Bull sharks owe their name to their stocky build, broad, blunt snout, and their behavior, which is considered comparatively aggressive and unpredictable.
Bull sharks are at the top of their food chains and were long considered solitary creatures. But now, a research team led by Natasha D. Marosi from the University of Exeter in the UK has examined their social behavior in greater detail.
Long-term study in the South Pacific
The study is based on six years of observations of a total of 184 bull sharks in Fiji, an island nation in the South Pacific. The sharks were divided into three age groups: immature juveniles, fully grown adults, and older adults after their reproductive phase. The researchers investigated how frequently two animals were within body length of each other, as well as which social interactions occurred, such as following a conspecific and swimming parallel.
The result was surprising: The bull sharks have an astonishingly complex social life and prefer certain members of their own species. "As humans, we maintain diverse social relationships—from casual acquaintances to our best friends. But we also actively avoid certain people—and these bull sharks behave similarly," explains Marosi.
Who swims with whom
The sharks preferred to interact with conspecifics similar in size. It was also noticeable that both males and females more frequently sought the company of other females. However, males were the most social overall. Furthermore, it was shown that adult animals form the "core" of the social network, while very old and not yet fully grown sharks are significantly less involved.
Overall, older bull sharks are less socially active. "These older individuals have honed their hunting and reproductive skills over many years. For them, social behavior may be less crucial for survival than for animals in their middle years," explains Marosi.
What does friendship bring in the ocean?
However, the precise role these social bonds play in the animals' daily lives is not yet fully understood. “We are only at the beginning of truly understanding the social lives of many shark species. Like other animals, they likely benefit from being social—for example, by learning new skills, finding food or potential mates, and avoiding conflict,” says Marosi’s colleague Darren Croft.
Marosi emphasizes the importance of better understanding the social behavior of shark species. This knowledge can help develop better frameworks for their protection and management. Currently, one of the study’s sponsors, the Fiji Shark Lab, is working with the Fiji Department of Fisheries to incorporate the study’s findings into joint conservation measures.
Source: University of Exeter
