Shark Social Life

By Tanya Brunner, MS

Sharks are often regarded as recluse. We envision them as solitary, cruising the oceans alone. Surprisingly, some species form established groups with hierarchies, and many even interact with other fish in nonthreatening, mutual relationships.

Not all shark species are solitary

EC_scallopedHH_galapagos.jpgForming groups provides several advantages. Aggregating might help with migration, it confers greater protection from predators, and it allows sharks to locate and capture prey more efficiently (Klimley and Nelson 1981).

Cooperative hunting has been demonstrated by blacktip reef sharks, and is likely employed by oceanic whitetip, thresher, and sandtiger sharks (Wetherbee et al. 1990).

Many sharks, like blue sharks, hammerheads, and spiny dogfish, spend much of their lives segregated by gender and age (Campagno et al. 2005). Scalloped hammerhead sharks form different groups: Subadult females live offshore with similar-sized individuals. They feed in the pelagic zone where they grow and reach maturity rapidly, and eventually seek males for mating (Klimley 1987). In the Gulf of California, schools are sometimes composed of both sexes (Klimley and Nelson 1981).  The males and females of some species purposely gather only during their mating period (Mojetta 2004). 

 

Sharks co-exist peacefully in groups

MO_carribeanreef7.jpgIt is conventional for shark groups to have established hierarchies, established by size, with smaller individuals acting as subordinates (Myrberg and Gruber 1974; Guttridge et al. 2009).

Great whites display dominance based on size, but typically avoid confrontational interactions with one another.

Like many terrestrial animals, sharks also establish territories, or show site fidelity, and are competitive with other individuals, both of the same and different species. Competitions generally arise when different species share similar food preferences (Mojetta 2004). Instead of fighting for territories, different shark species with the same taste in prey may have different distributions (Papastamatiou et al. 2006); this dispersal allows each species to exploit their preferred resources in different locations.

Still, sharks can and do co-exist peacefully in a shared environment. In the wild, reef sharks like blacktips form social groups, existing as a community composed of several groups in a particular location (Mourier et al. 2012). The sociability of sharks is further demonstrated by their ability to live peacefully in aquariums where different species of sharks are often on display in the same exhibit.

 

Sharks create partnerships with other fish

MO_lemon5.jpgNot all interactions sharks have with other fish are for feeding. Some purposely associate with other fish, forming mutual symbiotic relationships where both species benefit from one another.  One example of this interaction is seen at cleaning stations, typically found on reefs, where small fish and shrimp remove dead skin, mucus, and parasites from sharks. Even rays display this behavior (O’Shea et al. 2010).

The sharks, or clients, approach these stations, allowing their cleaners to move across their bodies, into their gills, and sometimes even through their mouths (Sazima and Moura 2000). In return for receiving a thorough cleanse, the clients at these stations provide their cleaners with food. 

References

Campagno, L., M. Dando, and S. Fowler. 2005. Princeton Filed Guides: Sharks of the World. Princeton University Press: Princeton, New Jersey. Pg. 42.

Guttridge, T. L., A. A. Myrberg, I. F. Porcher, D. W. Sims, and J. Krause. 2009. The role of learning in shark behaviour. Fish Fisher. 10:450-469.

Klimley, A. P. 1987. The determinants of sexual segregation in the scalloped hammerhead shark, Sphyrna lewini. Env. Biol. Fishes 18(1):27-40.

Klimley, A. P. and D. R. Nelson. 1981. Schooling of the scalloped hammerhead shark, Sphyrna lewini, in the Gulf of California. Fish. Bull. US. 79:356-360.

Mojetta, A. 2004. Underwater World: Sharks. White Star: Vercelli, Italy. Pg. 102, 116

Mourier, J., J. Vercelloni, and S. Planes. 2012. Evidence of social communities in a spatially structured network of free-ranging shark species. An. Behav. 83(2):389-401.

Myrberg Jr., A. A. and S. H. Gruber. 1974. The behavior of the bonnethead shark, Sphyrna tiburo. Copeia 1974(2):358-374.

O’Shea, O.R., M. J. Kingsford, and J. Seymour. 2010. Tide-related periodicity of manta rays and sharks to cleaning stations on a coral reef. Mar. Fresh. Res. 61:65-73.

Papastamatiou, Y. P., B. M. Wetherbee, C. G. Lowe, and G. L Crow. Distribution and diet of four species of carcharhinid shark in the Hawaiian Islands: evidence for resource partitioning and competitive exclusion. Mar. Eco. Prog. Ser. 320:239-251.

Sazima, I. and R. L. Moura. 2000. Shark (Carcharhiuns perezi), Cleaned by the Goby (Elacatinus randalli), at Fernando de Noronha Archipelago, Western South Atlantic. Copeia 2000(1):297-299.

Wetherbee, B. M., S. H. Gruber, and E. Cortes. 1990. Diet, feeding habits, digestion, and consumption in sharks, with special reference to the lemon shark, Negaprion brevirostris. In Elasmobranchs as living resources: advances in the biology, ecology, systematics, and the status of the fisheries. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 90:29-47.

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