76 Sharks: The Animal Answer Guide
Hammerheads mentioned above. Among Scalloped Hammerhead females,
central positions within the group seem to be favored, and these positions
are most often occupied by larger animals. Spacing between sharks and po-
sition in the group are enforced by several displays. Larger females displace
smaller animals by swimming toward the smaller shark and performing an
underwater spinning backflip, referred to as “corkscrewing,” something
worth trying at home. Smaller females respond to this display by moving
away, usually towards an outer position within the group. At a higher level
of aggression, a large female may swim over a smaller one and strike down
with her head on the head of the smaller shark in a motion similar to the
way that hammerheads “hammer” stingrays into the bottom (see “How do
sharks catch their prey?” in chapter 7). Again, the smaller individual usually
moves off to the edge of the group after being struck.
Displays similar to those of the Gray Reef Sharks have been seen in
Galapagos, Silky, Lemon, Blacknose, and Bonnethead sharks; and a Bull
Shark performed exaggerated swimming before attacking a small boat that
had been following it. These sharks and Scalloped Hammerheads are all
members of two closely related families, the Carcharhinidae and Sphyrni-
dae, so it would not be surprising if other species in these families also
maintain personal space via similar displays. Defense of personal space may
also explain a behavior known from Sand Tiger Sharks. Female Sand Tiger
Sharks off the Natal Coast of South Africa perform a tail whipping be-
havior that sounds like a whip cracking. This tail whip-cracking has been
directed at divers who approached the sharks in caves and could be a keep-
away signal.
Basically, if you approach a shark and it starts to act strangely, consider
it a warning you shouldn’t ignore.
If we expand the definition of a territory to include defending an object
rather than just a piece of turf, we can include defense of food as a type of
territoriality. Sharks will defend food against other sharks. White Sharks
perform displays toward other White Sharks around food, including par-
allel swimming and slapping the tail on the surface in the direction of an-
other, approaching White Shark.
Home ranges are often distinguished from territories. A home range,
sometimes called an activity space, is the area where an animal spends most
of its time, regardless of whether it defends it or not. Many shark spe-
cies have well-defined if not constant home ranges. Horn Sharks constrain
their activities to a relatively small home range of about 1,000 m^2 (11,000
ft^2 ), which is about twice the area of a basketball court. The area includes a
shelter site for daytime resting and may be used by an individual for a de-
cade or more. Some other sharks with known home ranges include Black-
tip Reef Sharks (about 0.5 km^2 , or about 0.2 square miles) and Gray Reef
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