Read shark researcher Mark Marks' responses on the following shark topics:

Disappearing sharks
Shark evolution
Shark deterrent?
Nonstop swimmers?
Shark posturing
Swimming with the sharks?
Shark diving
Shark education
Shark enemies
Shark reproduction
Great white disposition
Favorite shark
Shark eyes
Shark companions
Bite pressure
Bladderless sharks
Warmblooded killers
Hammerheads
Thresher sharks
Great whites in captivity
Shark protection

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Q: On Shark Posturing

I know other smaller sharks show a postering move with their backs arched, fins down and a twisting motion. Does the white shark do that?

Thanks ahead of time,
Tom LaRosa

A: Dear Tom,
You are referring to the exaggerated swimming-threat posture known as "agonistic display," which was first observed in the gray reef shark, Carcharhinus amblyrhynchos. Some species of shark will demonstrate their social position (rank) in a type of dominance-based social hierarchy through physical posturing; that is, by displaying and directing an overt visual signal to a potential competitor or foe. Agonistic displays tend to be sets of ritualized behaviors often observed in large carnivores. These behaviors are typically seen within a territorial context, and are intended to avoid physical confrontation (better to signal your intent first before going to blows and risking possible injury!). If however, the threat is ignored, the encounter will often escalate into a contact fight. Considering the weapons these sharks possess — a mouth studded with razor-edged teeth — it makes biological sense for them to clearly broadcast their intent...social faux paus can be costly, as well as painful! While conducting a six-year study on the behavioral ecology of white sharks in South Africa, I described and categorized social behaviors exhibited in white sharks, many of which are much more subtle than the visually loud "hunching" of the gray reef shark. Other signals, however, are literally in your face and unmistakable, such as "gaping," by which a shark displays its weaponry, i.e. its full complement of large, white, triangular teeth.

Did you know that sharks are quite sociable? Listen to an audio interview with Mark Marks.