November 2019, ScientificAmerican.com 19RICARDO SOLAR
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By Jennifer LemanANIMAL BEHAVIORFeather Trap
Brazilian ants build an
unusual pitfall for bugsFallen feathers may appear innocuous, but
bugs in tropical Brazilian savannas should
think twice about approaching them. New
research suggests Pheidole oxyops ants
sometimes place feathers around their
underground nest’s single entrance as bait
for other creatures, which then tumble in.
This behavior is an unusual example of ants
using lures or traps rather than actively
hunting down their prey.
Inácio Gomes, an ecologist at the Fed-
eral University of Viçosa in Brazil, had nev-
er seen any description in scientific studies
of ants building traps. He first noticed
feathers around ant nest entrances in city
parks and on his college campus, and he
found two hypotheses in scientific litera-
ture: the feathers could collect morning
dew in dry areas, or they could act as lures.
Gomes is lead author on an August
study in Ecological Entomology that experi-
mentally tested both ideas. The research-
ers provided a ready supply of wet cotton
balls but found the ants still collectedfeathers, suggesting they were not being
used for water. And the team found that
artificial traps with feathers around them
captured more wandering arthropods than
those without.
Gomes says that once prey such as
mites, springtails or other species of ants
fall in, the nest entrance’s soft walls make
it hard for them to climb out, and the
inhabitants quickly subdue them.
Helen McCreery, a biologist at Harvard
University, who was not involved in Gomes’s
research, says the study is “really cool” and
well done. “It’s a very charismatic, conspicu-
ous behavior,” McCreery adds. “There arecertainly very few examples of ants acquir-
ing food without leaving their nest.”
McCreery wonders why prey are attract-
ed to the feathers in the first place; Gomes
suggests smell and shape are potential
draws. “In general, soil insects are very curi-
ous—that’s why pitfall traps are so effective,”
Gomes says. Scientists use similar traps to
capture wild specimens.
P. oxyops forage alone or in groups like
other ant species—Gomes once saw them
take down a praying mantis—but he said
they most likely supplement hunting with the
feather traps to get through long dry seasons
with scarcer prey. — Joshua Rapp LearnCAMEROON AND
EQUATORIAL GUINEA
Scientists found that
Goliath frogs, which are
Earth’s largest living frogs
and can be longer than a
football, construct protect-
ed ponds for their young
by pushing heavy rocks
across streams. They live
only in this region.
TANZANIA
Marine biologists discovered a colorful fish
species, dubbed the vibranium fairy wrasse,
during a biodiversity assessment of largely
unstudied deep reefs off Zanzibar’s coast.MEXICO
Researchers have rationed
electricity and cut
temporary employees’
jobs after Mexico’s
president lowered funding
for federal institu tions,
including those supported
by the National Council
of Science and Technology,
by 30 to 50 percent in
certain budget items. COLOMBIA
Scientists confirmed a destructive fungus targeting
banana plants has arrived in the country. No
treatment is available, so officials put potentially
infected crops under quarantine to stop its spread.GERMANY
A vengeful crowd attacked two intoxicated German
men who killed a western capercaillie they said
attacked them. The bird is endangered in Germany;
species populations have shrunk because of habitat
loss and stress from increased human contact.CANADA
In the famed Burgess Shale rock formation,
paleontologists discovered hundreds of fossils
from a horseshoe crab–shaped, prehistoric
predator that lived in the ocean 506 million years
ago. It measured up to a foot long.Pheidole oxyops nest entrance
is surrounded by feathers.For more details, visit
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