Family ties shape social lives of bull sharks
Bull sharks have a slight preference for spending time with their relatives, new research shows.
New research published in Ecology and Evolution reveals that bull sharks, despite being large apex predators, have a slight preference for associating with their relatives. The study, titled "Is Blood Thicker Than Water? The Influence of Kin Within a Bull Shark Social Network," examined six years of observations at Shark Reef Marine Reserve in Fiji, where adult bull sharks regularly gather.
Using genetic data, scientists discovered that most sharks are not closely related, but individuals are more likely to socialize with relatives. Researchers coined the term "kinfluence" to describe the influence of kinship on shark social structure and behavior. While this effect is not as strong as other factors like sex, age, and size, it is still significant.
The study found that family ties influenced both proximity-based associations and directed social interactions, such as parallel swimming and joining swimming behaviors. These social preferences were particularly evident among male sharks. Evolutionary theory suggests that animals tend to favor their relatives, promoting shared genes.
It remains unclear how sharks identify their relatives, but early life in shared rivers and estuaries could help them recognize kin later in life. However, family ties may play an even more significant role in bull shark social structure, given the high mortality rates of young sharks in river and coastal habitats due to illegal fishing.
The findings challenge the perception of sharks as solitary, fearsome creatures and highlight the complexity of their social networks.
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