D NA t e s t s s o lve mys t e r y o f
g i a n t ' l i o n - k i l l i n g ' a p e s
People living around the town of Bili, about
200 kilometers east of the Ebola river, have
long swapped stories of ferocious apes with a
penchant for killing lions (New Scientist, 9
October 2004, p 32). The apes seemed too
large to be chimps. From photographs, they
were estimated to weigh up to about 100
kilograms, and their footprints at up to 34
centimeters long were bigger than a gorilla's.
To solve the mystery Cleve Hicks and
colleagues at the University of Amsterdam, the
Netherlands, spent a year in the field tracking
the apes. During that time, Hicks logged an
unprecedented 20 hours observation. "I see
nothing gorilla about them," he says. "The
females definitely have a chimp's sex swellings,
they pant-hoot and tree-drum, and so on."
Analysis of mitochondrial DNA taken from
faecal samples also puts the animals within the
Pan troglodytes schweinfurthii group. Hicks is
now analyzing samples of nuclear DNA in the
expectation that this will rule out a chimpgorilla
hybrid. "I would say that possibility is
negligible," he says.
The Bili apes are, nevertheless, unusual. Their
skulls have a gorilla-like sagittal crest, but also
many chimp-like features. Recordings reveal
that they howl during the full moon. The apes
live at high density. Hicks found 430 nests in a
160-kilometer trail system. "At least some are
definitely night nests," he says, which is
atypical for a chimp. While gorillas nest on the
ground, chimps usually bed down in trees.
Hicks says the animals regularly smashed up
termite mounds, and used tree roots and rocks
as anvils for breaking open fruit and, in one
instance, a forest tortoise. They also use sticks
up to 2 metres long to dip for driver ants, and
shorter sticks to fish for other invertebrates.
Colin Groves of the Australian National
University in Canberra has studied skulls
collected from the region. He thinks that the
Bili skulls are unusually large, but that
morphologically they are a unique population
of P. t. schweinfurthii.
About 18 kilometers north-west of Bili, Hicks
discovered a large population in which the
density of the animals is much greater. What's
more, they do not appear to have encountered
humans before. "It's fantastic. They surround
us and show curiosity - even the adult males,"
he says. "It is these guys we want to study."
From issue 2558 of New Scientist magazine, 30
June 2006, page 14