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How do Sperm
Whales Catch Squids?
 Vision
may play a central role in sperm whale predation. Two complementary
hypotheses regarding the detection and capture of prey items are
presented, based on a review of mesopelagic ecology. The first
hypothesis postulates that sperm whales locate their prey visually,
either silhouetted against the midwater "sky," or by searching
for bioluminescence produced by the movements of their prey. The
second hypothesis postulates that sperm whales create a zone of
stimulated bioluminescence around the mouth, which attracts squids
and other visual predators. Studies of midwater fishes and invertebrates
document the importance of vision in mesopelagic communities.
If sperm whales search for silhouetted prey, they should be oriented
upside-down to improve visual coverage and to facilitate the transition
from search to prey capture. Prey capture events should be marked
by excursions toward the surface. If they lure their prey, they
should swim at a steady pace, with little rapid acceleration,
and spend most of their time foraging at depths with the greatest
potential for stimulated bioluminescence. |
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