Monday, July 23, 2012

Are Sharks Social?: Australian researcher studies social interaction of Port Jackson sharks

A great white shark seems to keep its distance from its fellow white sharks.  Even when I have had the opportunity to have as many as five white sharks circling around me, they still keep a respectable distance from each other and rarely came close to each other.

Then on the other hand, you have hammerhead sharks that can be seen swimming in large schools.  Lemon sharks or various types of reef sharks congregating in the tens and sometimes hundreds.  And I have seen seasonal congregations of up to 4-5 foot leopard sharks and guitarfish in Southern California, presumably part of a breeding behavior.

The social interactions of sharks is not well understood.  Each species has its own type of behavior and while the general public thinks of sharks as somewhat solitary (which they often can be), in reality it is more likely a very complex relationship that revolves around feeding, breeding, and a predator's sense of territoriality (ie: survival). In Australia, one researcher is specifically focusing his efforts on understanding the social behavior of sharks.   Working in conjunction with the Taronga Zoo in Sydney, Australia, Nathan Bass intends to study the patterns of interaction between Port Jackson sharks, a smaller, predominantly bottom-feeding species similar to the horn shark found along the Pacific coast of the U.S.

“Port Jackson sharks have some really interesting interactions,” says Bass. “These types of sharks can be solitary, but they often occur in large groups around breeding time. They are apparently social while resting and seem to favour their resting sites, frequently with more than 30 individual sharks recorded together in one area alone.”

Bass will be attaching acoustic transmitters, known as "tags," to several sharks to track their movements.  Tags have long been used in shark research often to study the animal's regional hunting movements or longer migratory journeys.  By attaching tags to a large number of Port Jackson sharks, Bass hopes to be able to correlate their movements and possible interactions with seasonal events such as known breeding periods to determine possible social behavioral patterns.

“What we’d like to find out is whether Port Jackson sharks are frequently congregating with the same individuals for social reasons, and if they are, whether they prefer to socialise with individuals of the same sex and size or rather with individuals they’re related to,” said Bass.

An understanding of the social behavior of one species of shark does not necessarily  open the floodgates of enlightenment regarding sharks as a whole.  But it is a solid first step and provides a sort of baseline with a set of behavioral assumptions that can be tested with other species.  Insight into the social behavior patterns of sharks, no matter how social or anti-social these animals prove to be, will provide us with a better understanding as to their role in the maintenance of a healthy marine ecosystem and what the implications are with the loss of one or more of these important predators within a specific area.


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