In a new study published in PLOS ONE titled, "White sharks (Carcharodon carcharias)
scavenging on whales and its potential role in further shaping the ecology of
an apex predator," Captain Chris Fallows from Apex Expeditions
collaborated with University of Miami (UM) scientists Dr. Neil Hammerschlag and
Austin Gallagher, to explore the behaviors of Great white sharks scavenging on
dead whales in South Africa.
The team documented as many as 40 different sharks
scavenging on a carcass over the course of a single day, revealing unique social
interactions among sharks.
Sharks off SA coast
The study summarized observations based on four scavenging
events opportunistically observed over a 10 year period. In each multi-day
observation, the team recorded daily evidence of social, aggregative and
feeding behaviours observed in the waters off South Africa.
They suggest that although the occurrence of coming upon a
whale carcass may be sporadic, the shark populations are likely prepared to
scavenge on them, and may even rely on their scavenging activities to supplement
their regular feeding activities.
"Although rarely seen, we suspect that as white sharks
mature, scavenging on whales becomes more prevalent and significant to these
species than previously thought," said Hammerschlag, who is director of
the R.J. Dunlap Marine Conservation Program at UM.
The team found that sharks showed a clear preference for
scavenging on the blubber, probably because these high calorie meals can
sustain the sharks for longer periods of time. Interestingly, though, the study
also found that sharks showed an initial preference for feeding on the whale's
fluke before moving on to feed on the rest of the carcass. The team also found
that while scavenging on whales, they ceased hunting and feeding on seals, one
of their primary natural prey.
"While scavenging on the whale, the sharks clearly
showed a size-based pecking order," said Fallows. "The biggest sharks
came right in, targeting areas of highest blubber content, while smaller sharks
fed on areas with less blubber or kept their distance from the whale, mostly
scavenging on pieces of blubber that drifted away from the carcass."
Sharks may swim
around looking for carcasses
The paper reveals how the social and size structure of
sharks at the carcass appeared to be influenced by environmental patterns.
"The cues, such as the oils, emanating from this pulse of food are likely
attracting much larger sharks over 4.5 meters from long distances to
scavenge," said Gallagher. "These data provide some credence to the
hypothesis that large white sharks may be swimming known ocean corridors looking
for dead, dying, or vulnerable whales."
"By attracting many large white sharks together to
scavenge, we suspect that the appearance of a whale carcass can play a role in
shaping the behaviours, movements, and the ecosystem impacts of white
sharks" said Hammerschlag. "These patterns may shed some light into
the ecology of this often studied - yet still highly enigmatic - marine