Shark Ecology 99
mens plus visual sightings by divers of four animals along 300 km of the
eastern coastline of South Africa. The Java Stingaree (Urolophus javanicus)
is another species known from a single specimen. It was collected near Java,
Indonesia, 150 years ago and hasn’t been found since.
When during the day are sharks most active?
Sharks as a general rule are more active at night than by day, although
their opportunistic nature means they will take advantage of an easy meal,
such as a dead fish or baited hook, almost anytime. A common pattern,
then, is resting by day—alone or in groups, on the bottom or swimming
slowly—then moving at dusk to a nighttime feeding area (see “Are sharks
social?” in chapter 4). In many species, activity times are determined as
much by food availability as by light levels. Plankton-eating sharks such
as Whale and Basking sharks feed during daylight or we wouldn’t have
so many great photos of them. But their activity patterns as revealed by
depth-recording tags suggest they also feed at night, following moving
prey up and down in the water.
Manta rays—also plankton eaters—appear to feed both during the day
and the night; some of the most dramatic videos of feeding mantas have
been filmed at night. Many stingrays and skates forage actively during the
day, but torpedo rays and angel sharks are more active at night. One excep-
tion is the Ornate Sleeper Ray, which vacuums up worms by day. White
Sharks can feed anytime, but they tend to hunt seals during daylight and
especially at dawn and dusk because that is when seals leave and return to
their rookeries and when White Sharks can take advantage of backlighting
to strike upward at a seal at the surface preparing for or recovering from a
foraging dive.
How do sharks survive the winter?
Because they are oceanic animals and live mostly away from the shore-
line, winter survival isn’t a big issue for most sharks, especially tropical spe-
cies. Some species that live at higher latitudes move seasonally but mainly
to follow their food, migrating to places where food will be more abun-
dant (see “Do Sharks Migrate?” above). Basking Sharks leave northern re-
gions in the fall, moving south to warmer areas, but they then swim in
cool depths, so they aren’t gaining any great temperature advantage. Spiny
Dogfish spend spring and summer off the west coast of Canada and move
south in fall and winter.
Like many sharks and bony fishes, some rays and skates in the North-
ern Hemisphere move offshore or south to warmer waters in autumn, sug-