Historically known to be one of the most plentiful shark species in the world, unfortunately, oceanic whitetip sharks have faced significant population declines globally from overfishing and the global trade of their fins, which are extremely valued in the shark fin soup market.
Science In The Spotlight
Since oceanic whitetips are widespread, it’s challenging to identify undiscovered aspects of their life history and behavior. During a week-long expedition at Cat Island, Bahamas, researchers noticed a group of three female oceanic whitetips swimming together in an evenly spaced straight-line formation, with the largest female in the middle. Since oceanic whitetips are usually solitary and only come together to mate, the researchers predicted that this new social behavior might be related to mating or competition.
Investigating a Potential New Social Behavior in Oceanic Whitetip Sharks:
Follow The Leader
Scientific Study: Novel social behaviors in a threatened apex marine predator, the oceanic whitetip shark Carcharhinus longimanus by Austin J. Gallagher, Joe Romeiro, Debra Canabal, Vincent Canabal, and Neil Hammerschlag
Top Predator
Animal reproduction has always been a fascinating and complex topic in biology. Today, it’s crucial to understand these concepts to conserve species and prevent biodiversity loss. Top predators, such as sharks, are vital to maintaining a balanced ecosystem but are also at high risk of extinction. Therefore, studying their biology and behavior is essential to predict how they’ll be impacted by global change. Large predatory sharks, in particular, are becoming increasingly threatened globally, but it’s difficult to study them since they’re rare and elusive, frequently diving to inaccessible depths and traveling thousands of kilometers across oceans.
Discovering New Social Behaviors
From April to June, many oceanic whitetip sharks gather near Cat Island, Bahamas. Many tour companies use bait to attract the sharks closer to dive tourists. Adult female sharks make up most of the group, with male sharks occasionally stopping by. Recently, scientists went on a week-long trip to the Bahamas and discovered new social behaviors among these sharks. They believed these behaviors might be related to mating or competition and compared them to those seen in other predatory sharks. The researchers also discussed the potential impact of these behaviors on the environment and the conservation of top predators.
Follow The Leader
In 2013, a study was conducted near Cat Island in the Bahamas. The study area was a shallow reef that dropped into a deep oceanic trench. Observations were made from April 22 – 25 for 8 hours each day. During the study period, researchers observed between 8 and 15 adult female sharks each day, and on April 25, the first male shark was observed. This male shark exhibited hostile and unpredictable swimming behavior toward the divers and nearby females. At noon on the same day, three female sharks formed a straight line with an equal distance of 0.5 meters between them. The largest female was positioned in the center of the line. The group remained together for 8.5 minutes before breaking up. This behavior was observed an additional four times that day. The researchers learned from a local dive operator that this behavior is common during aggregation season.
Getting To Know You
When marine predators gather in one area, it can lead to social interactions and mating that may not occur when they are spread out. The researchers believed that the behaviors they witnessed in the female oceanic whitetip sharks might be because they were looking for a mate or competing with each other. It was hard to study these behaviors because these sharks are hard to track and observe in the open ocean. Although the researchers only observed them for a week, they believed these behaviors were important to understand the social lives of these sharks better.
Looking For A Mate?
The nose-to-tail swimming patterns observed in the three female oceanic whitetips may be a way for the female sharks to show that they are ready to mate and also to protect themselves from males who might harass them. This behavior has also been observed in other shark species, like basking and white sharks. In the past, similar behaviors have been observed in scalloped hammerhead sharks, where the biggest females were in the center of the group, which could help males to pick the healthiest females to mate with. It is unknown if males are causing these behaviors or if they happen before males arrive.
Put ‘em Up Just Put ‘em Up
Another possibility for the unique social behaviors observed in female oceanic whitetip sharks is that they are related to competition among individuals for the bait offered by divers. The sharks may be trying to establish dominance or assess their opponents’ willingness to fight. It’s also possible that these behaviors might be a response to the presence of humans and the use of bait to attract sharks to the area.
Keep Studying…
While it’s uncertain why the sharks behaved in the manner they did, it may be related to their life cycle. The researchers suggest that future research on these sharks should combine observations of their behavior with new technology to better understand them and help protect them.
References
1. Gallagher, A. J., Romeiro, J., Canabal, D., Canabal, V., & Hammerschlag, N. (2014). Novel social behaviors in a threatened apex marine predator, the oceanic whitetip shark Carcharhinus longimanus. Ethology Ecology & Evolution, 26(4), 413–417. https://doi.org/10.1080/03949370.2014.896831
2. Young, C. N., & Carlson, J. K. (2020). The biology and conservation status of the oceanic whitetip shark (Carcharhinus longimanus) and future directions for recovery. Reviews in Fish Biology and Fisheries, 30(2), 293–312. https://doi.org/10.1007/s11160-020-09601-3
3. Bester, C. (2018). Oceanic Whitetip Shark. Florida Museum. https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharhinus-longimanus/