SET against the 50 million years that ants have been farming, the 10,000-year
history of human agriculture is a mere blink of an eye. Now it seems that as
well as pre-empting our efforts at cultivation, ants have some neat tricks for
avoiding crop diseases too.
Panamanian leaf-cutter ants (Atta colombica) have a sophisticated
rubbish disposal system that protects their underground fungus gardens from
infestation. 鈥淚t鈥檚 so human,鈥� says Francis Ratnieks at Sheffield University,
鈥渢hey go to great pains to dump in a way that minimises contact with the
苍别蝉迟.鈥�
Cleanliness is vital because of a parasitic fungus called Escovopsis
that can devour the ants鈥� fungal harvest, he explains. The cultivated fungus
grows on leaves brought back by foragers. But contamination with
Escovopsis can destroy the colony鈥檚 crop.
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Ratnieks and his team have found that rubbish dumps of rotten garden fungus
and dead ants are located so as to avoid contamination, often several metres
away and downhill from the colony. 鈥淭his makes beautiful sense in terms of
avoiding flow back into the colony during flash floods,鈥� says Nigel Franks, an
ant expert at Bristol University. Ratnieks鈥檚 team will report their findings in
a future issue of Behavioral Ecology.
Other tactics are to chuck garbage into streams or from high points on nearby
plants or rocks. Ratnieks believes that this 鈥渇ly-tipping鈥� avoids the problem of
clambering over the garbage pile. Rubbish carriers even use a separate 鈥渦nclean鈥�
nest entrance, presumably to minimise contact with their nest-mates. Foraging
ants also observe a five-metre exclusion zone around the dump.