Oceanography | September 2018
Sanctuary. “Other baleen whales feed by
rapidly swimming forward, but humpbacks
are adapted for fine-scale movements that
allow them to create bubble nets.”
Humpbacks release the bubbles while
swimming in upward spirals, often during
a behavior called double loops. Double
loops starts with an ascending spiral to
corral fish, then the smack of a fluke on
the ocean surface and a second upward
lunge to capture the corralled prey. The
whales work in teams of two to 10 or more,
emerging at the ocean surface in a boiling
cauldron of open mouths. “The sequence
is as complex as the tool use of apes in
the forest,” says Wiley. He and colleagues
reported bubble netting and double loops
in 2011 in the journal Behaviour.
Further research has uncovered other
new-to-science whale feeding behaviors
such as bottom side-rolls and repetitive
scooping. The findings are detailed in a
2014 paper in Marine Mammal Science
coauthored by Wiley and others. In bottom
side-rolls and repetitive scooping, hump-
backs repeatedly dive to the seafloor,
roll onto their sides, tilt their heads down,
open their mouths, and expand their throat
pleats. They then swim along the bottom,
funneling in sand lance as they go.
Bottom side-rolls are common on
Stellwagen Bank and in the Great South
Channel, a deepwater passage between
Nantucket, Massachusetts, and Georges
Bank to the southeast.
Scientists wondered whether the whales
were bottom side-roll feeding when
they saw scars on the humpbacks’ jaws.
Indeed, humpbacks bottom side-roll for
extended periods wherever sand lance
are common. Research conducted this
summer is revealing new information on
humpbacks’ bottom-feeding techniques.
IT ALL COMES DOWN TO SAND LANCE
What’s driving all the bubble netting and
bottom feeding? Stellwagen Bank, with
its sandy bottom and relatively shallow
waters, is prime habitat for sand lance.
The bank’s abundant sand lance, which
travel in huge schools reaching the tens of
thousands, offer the whales high- calorie
meals. In one day, a whale might eat a ton
of the fish.
At night, sand lance burrow into sandy
sediments or form schools close to the
seafloor. During the day, the fish often
swim in dense mats along the seabed. The
humpbacks’ recently discovered feeding
techniques, especially side-rolling, result
in efficient fish-catching when the whales
Humpback whales blow bubbles to form “fishing nets” that capture sand lance. Image credit: NOAA/
NEFSC/Allison Henry; MMPA research permit #17355
Oceanography | September 2018