Monkeys filmed feasting on locust swarm in Ethiopia
By Jody Bourton
Earth News reporter
Extraordinary locust feast event filmed in Ethiopia
Geladas have been filmed feasting on a swarm of locusts in the highlands of Ethiopia, behaviour rarely seen before.
Scientists recorded the extraordinary scenes with a video camera as millions of desert locusts invaded the grasslands where the geladas live.
The primates are known to feed almost exclusively on grass, so eating insects this way is highly unusual.
The intensive feeding raises concerns that using pesticides to limit locusts can have adverse affects on wildlife.
The study is published in the journal Primates.
The event occurred in June 2009 on the Guassa Plateau, Ethiopia, located on the western edge of the Great Rift Valley.
Air currents allowed millions of locusts to travel up from from the Rift Valley to the alpine grassland 3500 metres above sea level.
Researchers have been studying gelada monkeys (Theropithecus gelada) in this location for years.
The 220 geladas around me uttered a series of screams, suggesting that they were initially afraid of what was happening
Dr Peter Fashing California State University, Fullerton, US
"The desert locust invasion at Guassa was the most amazing biological event I have witnessed in 17 years of studying primates in Africa," says Dr Peter Fashing from California State University, Fullerton, California, US.
Dr Fashing describes how a loud humming sound could be heard before the sky began to darken and massive numbers of the pinkish-brown locusts (Schistocerca gregaria) appeared.
"The 220 geladas around me uttered a series of screams, suggesting that they were initially afraid of what was happening," Dr Fashing says.
"They then began running rapidly and chaotically in pursuit of the locusts. It was remarkable to see geladas leaping high into the air to catch the locusts or pouncing on the locusts that had landed on the ground."
The researchers write that due to the chaotic nature of the event and the high speed of the animals it was difficult to follow and study individual geladas.
Dr Fashing undertook the research along with Dr Nga Nguyen also from California State University, Fullerton and Dr Norman Fashing of the College of William and Mary, Williamsburg, Virginia, US.
Other species joined the geladas to feed on the locusts, including an extremely rare Ethiopian wolf (Canis simensis) and thick-billed ravens (Corvus crassirostris).
"Feasting on locusts by geladas is interesting because geladas are known for being extreme dietary specialists," Dr Fashing says.
Geladas are the only primates known to subsist mostly on grass.
Though many birds species have been known to prey and sometimes track desert locusts swarms, little is known about the extent to which other vertebrates feed opportunistically on these insect aggregations.
The scientists explain the large influx of locusts meant animals were able to take the opportunity to switch diet and take advantage of the large source of protein.
However, the researchers' amazement is also tempered with concern.
"While, on the surface, the locust invasion at Guassa was a huge source of protein for the animals who ate them, our concern is that desert locusts are still primarily treated with pesticides in most of Africa, including Ethiopia when outbreaks occur," Dr Fashing says.
That means these pesticides may be passed onto species such as geladas or Ethiopian wolves, as not all of the locusts die during spraying operations.
"We have to be concerned about possible adverse affects that pesticide spraying might have on some of Ethiopia's most spectacular endemic wildlife," Dr Fashing says.
"Indeed, Ethiopian wolves and geladas are the two main flagship species for the conservation of the threatened Ethiopian Highlands ecosystem."
Increases to locust swarm activity in the highlands due to possible changes in climate could also make the situation worse.
"Desert locust invasions have never before been reported at elevations anywhere near as high as at Guassa," Dr Fashing says.
"We cautiously raise the issue in the paper of whether the invasion that occurred at Guassa could be linked to global warming.
"Only time will tell based on whether more desert locust invasions are reported in the future in the Ethiopian Highlands."