Shark Behavior 77
Sharks (0.2–53 km^2 , or 0.08–20 square miles). Half of 36 tagged female
Gray Reef Sharks in Palau remained within a few hundred meters of where
they were tagged over a 2.5-year period, with occasional movements away
from and back to their residence area. Such “site fidelity” is also considered
a characteristic of Nurse, Blacktip Reef, and Caribbean sharks, especially
among juveniles.
In Bimini, juvenile Lemon Sharks less than 1 m (3 ft) long initially pa-
trol shallow beach areas of about 70 ha (0.7 km^2 , or 0.3 square miles). This
area increases with age: a 1.8-m-long shark may have a range of 18 km^2 (7
square miles), while a 2.3-m-long shark’s home range encompasses as much
as 93 km^2 , or 36 square miles. Habitats also change with age, the shark
moving from shallow nursery areas to open sand flats and finally to the reef
and beyond. Whitetip Reef Sharks remain in small 1- or 2-km^2 areas (0.4–
0.8 square mile) for several days up to six years, but they also periodically
move between home range areas, sometimes traveling as far as 10 km be-
tween locales. Moving between different core areas appears to characterize
several of the few sharks studied to date. An individual can therefore have
several home ranges, staying for a while in one before moving to another a
few kilometers apart, as is true of Blacktip Reef and Whitetip Reef sharks.
We know less about home ranges in other taxonomic groups. Cownose
Rays are well known for their periodic long-distance migrations (see “Do
sharks migrate?” in chapter 5). But some individual rays in Florida stay in
fairly restricted areas for over a year. Average home range size for stay-at-
homes was about 22 km^2 (8.5 square miles), but they spent 50% of their
time in an area of only 3 km^2 (0.5 square mile).
Do sharks socialize with other kinds of animals?
Sharks don’t enter into ecological relationships with many other ani-
mals, unless you count eating or being parasitized by them as a relation-
ship. Some fishes follow sharks around, swimming just in front or under
their host. Several members of the jack family Carangidae, such as juvenile
Golden Trevally (Gnathanodon speciosus), do this. Pilot fish (Naucrates ductor)
are seldom found away from a shark or manta ray host.
One family of bony fishes is highly adapted for associating very closely
with sharks and rays. These are the remoras, or sharksuckers (family Ech-
eneidae). Smaller sharks may have one or two small sharksuckers attached,
but large species such as Whale Sharks and Manta Rays can have several
large hitchhikers. Remoras attach not only to sharks and rays but also to
marlins, whales, turtles, and an occasional diver. Remoras do this with an
evolutionarily modified first dorsal fin that can create strong suction pres-
sure. This allows the remora to remain attached to its host regardless of