148 Sharks: The Animal Answer Guide
(Journal of Morphology, Sept. 2008, p. 1041). As powerful as this may be, the
pressures fall off rapidly with distance, and it is unlikely that prey can be
inhaled from a distance much greater than about 3 cm (1.2 in).
Many sharks use suction to capture buried or hidden prey. Leopard
Sharks suck worms out of their burrows. Hemiscylliid sharks such the
Epaulette Shark and the Whitespotted Bamboo Shark shove their heads
into bottom sediments far enough to cover the first gill slit and suction up
worms and crabs. They then winnow the prey from the sediment by swish-
ing the mixture around in their mouths. The prey are then swallowed while
sand and silt are expelled out the gills.
Batoid rays use suction as much as or more than selachian sharks do.
The Lesser Electric Ray (Narcine bancroftii) specializes in wormlike prey,
apparently including small, eel-like fishes. Instead of sticking its head
into the sand, it protrudes its jaws—which when extended are as long as
its head—deep into bottom sediments and suctions up prey (and sand).
The mixture is winnowed in the mouth and the sediment expelled out the
mouth, spiracle, or gill slits.
Suction can be applied to the task of feeding in other, unexpected ways.
Cownose Rays employ “hydraulic jetting.” They sit on the bottom, bal-
anced on the tips of their pectoral fins. They then repeatedly open and
close their mouths three times per second, drawing water in and shooting
it back out. The jet of water thus created is directed at the bottom, where
clams and sand are suspended. The sand is progressively flushed away by
the stream while the heavier clams remain (see also “Do sharks use tools?”
in chapter 4).
The ability of many batoids to use suction pressure in their feeding has
even led to the naming of a new species. A rare electric ray from South
Africa, the Ornate Sleeper Ray (Electrolux addisoni), was known to scuba
divers before one was captured and officially described in 2007. Divers had
videotaped the animal and showed that it feeds by moving slowly along the
bottom, protruding its jaws and inhaling worms by means of a “vigorous
sucking action,” reminiscent of a vacuum cleaner.
Filter Feeders. Large filter feeders like Whale, Basking, and Mega-
mouth sharks and manta rays don’t need much stealth or speed to capture
the zooplankton—small floating animals—that they eat. The challenge isn’t
so much outrunning the prey as it is keeping it from slipping past the filter.
Each one of these giant filter feeders accomplishes this in a slightly differ-
ent manner, with food captured on gill rakers, which are inward-facing,
fingerlike extensions from the gill bars that support the gill filaments in-
volved in breathing. Technically, these structures are referred to as “filter-
ing pads,” and they differ in each species. Basking Sharks have bristlelike
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