Blacktip reef sharks are one of the most commonly encountered shark species in Southeast Asia. For many divers, spotting a blacktip is a highlight of the dive. These sharks normally hang out on shallower reefs, making them easy to spot even for snorkelers. However, they are very shy and can be easily scared away.
Blacktip reef sharks are not just solitary predators. They often form groups and exhibit a fascinating and complex social life.
Dr. Mouriers research
In 2008, Dr. Johann Mourier started to study the social behavior of blacktip reef sharks in Moorea, French Polynesia. For several years, he documented the complex interactions and social networks of these sharks, revealing that blacktip reef sharks are much smarter than you would think and have a remarkably complex social life.
In 2011, his research came to a sudden stop when Chinese fishermen captured many of the sharks, decimating the population he had been studying.
Navigation skills
The research showed that blacktip reef sharks have impressive navigation skills, traveling long distances across the ocean. They often return to the same locations suggesting that they remember specific locations, such as rich feeding grounds or safe resting areas.
Making friends
They don’t just swim randomly over the reef as you would expect. Blacktips patrol their territory by swimming in particular patterns, often ‘teaming up’ with other sharks.
When a blacktip reef shark returned to the reef and rejoined the other sharks after a period of absence, the swimming pattern became more jagged and irrational. This indicates that the sharks could recognize each other and were ‘excited’ to see their ‘friends’ again.
Teaching the young
The study also revealed that blacktip reef sharks engage in social learning. Younger sharks observe and mimic the behavior of older, more experienced individuals. This helps the young sharks to navigate their environment, and learn social behavior and hunting techniques. Crucial survival skills that they might not learn independently.
Communication
In addition to learning, blacktip reef sharks use body language to communicate within their social groups. Specific movements can signal different intentions or states. For example, rapid flicking of the tail can signal agitation or alertness, indicating that the shark is on high alert or ready to react. Arching its body is a signal that asserts dominance or simply tells other sharks to back off.
These subtle cues help sharks to maintain cohesion within their group and ensure smooth social interactions.
Declining numbers
Although still commonly encountered by divers, blacktip reef shark populations have declined rapidly due to overfishing, habitat destruction, and the shark fin trade. Coastal development and coral reef degradation also contribute to their diminishing numbers.
Dr. Mourier’s research shows the complex social lives of blacktip reef sharks, revealing that they are far more than solitary ocean predators. They form and maintain complex social structures and they are able to learn and communicate.
Disruptions to their social networks can have significant impacts on their populations. Protecting these networks is crucial for the long-term survival of these beautiful and socially complex animals.