Ants that beat up elephants help shape the forests of Africa, according to researchers.
Jacob Goheen of the University of Wyoming published a study on the effects of ants on the African savannah last week. The study looks at how ants protect certain trees from elephants, changing the shape of forests.
“Savannas are somewhere between grassland and a forest,” said Goheen, a professor of zoology and botany. Elephants help control the extent of savannah by eating trees — too many, and it becomes grassland; too few, and it becomes forest. He and Todd Palmer at the University of Florida set out to study the effects of elephants at an elephant sanctuary in Laikipia, Kenya.
The team used fences to keep elephants out of parts of a forest and then studied satellite images of the region over five years. Elephant-free plots gained more trees over that time compared to normal ones, as expected, but only if they contained red, sandy soil. Plots with clay-like soil showed little difference in tree cover during the study, despite an almost three-fold increase in elephant numbers in the region.
The difference turned out to be ants. The clay regions were dominated by an acacia tree that housed swarms of ants in its thorns, which swell to the size of ping-pong balls. Whenever the trees were attacked, the ants fought back by biting the attacker. These trees were much less common in red, sandy plots.
Goheen and his team set out test trees for the elephants, some with ants and some without. They found that the elephants ate acacia branches when the ants were removed, but avoided branches from a species they’d normally eat when the team put ants on them — kind of like how most people avoid liver, he said.
“Elephants are unique in that what they use to feed with, their trunk, has a nostril on it,” Goheen said. Ants rush into those nostrils while the elephant eats and start biting — elephants have been seen sneezing the ants out when this happens. This protects the host tree from the elephant, preserving the forest and changing the African landscape. The ants do not work on giraffes, he noted, as they flick them away with their long tongues.
The big question is why these ant-covered trees haven’t taken over the savannah, Goheen said. He suspects that elephant foot-traffic might change the region’s soil, limiting the spread of the trees.
The study can be found in this week’s issue of Current Biology.
Medicines of the future might come from the brains of cockroaches, say scientists.
Veterinary medicine researcher Simon Lee of the University of Nottingham spoke on his study on bug brains and antibiotics at a meeting of the Society for General Microbiology this week.
Cockroaches and locusts live in dirty, disease-ridden environments, Lee said in an interview, so he and his team thought they might have defences against pathogens. They took molecules derived from the brains, fat, blood, and muscle of these bugs and tested their effects on antibiotic-resistant Staphylococcus aureus and E. coli bacteria.
They found that nine types of molecule from the bug brains destroyed about 90 per cent of the bacteria without harming human cells, Lee said. “The brain and central nervous system are crucial to the survival of the organism,” he noted, which is likely why the bug brains had this disease protection.
This is very early research, Lee said, but it could one day lead to new bug-based drugs that could fight antibiotic resistant disease. “We are still many years away from the ‘take two locusts and call me in the morning’ stage,” he said.
