Mass Hysteria in Baboons at Dutch Zoo Remains a Mystery

A group of baboons in a zoo in Netherlands surprised the zookeepers earlier this week by giving up usual activities and sitting huddled in a corner.

Emmen Zoo said that the baboons looked frightened and just sat in a corner together. The monkeys even gave-up eating their favorite food. The Zoo said that this isn't the first time that the monkeys exhibited such behavior. This has also happened earlier in 1994, 1997 and 2007.

However, the monkeys have now gotten a bit back to normal and some of them have resumed eating fruits, the zoo said. But, biologists haven't been able to explain this strange behavior.

"The first deviation we saw was on Monday evening. We were going to bring them to the night enclosure - it normally takes a minute for all 112 to enter, but it took more than an hour to get them all inside. Then the next morning it was a problem to get them out, and then they were immediately sitting in the trees and on the rocks doing nothing at all," Wijbren Landman, a biologist at the zoo told told BBC News.

Hamadryas baboons are native to the deserts of Africa and the Arabian Peninsula. The animals rarely stay away from their watering holes and have an intriguing social structure. Each group has one male who controls about ten males. These one male units (OMU) are the basic structure of the baboon society and multiple OMUs form a clan. Collective clans make a band. Multiple bands then make a troop of these baboons.

Previous research has shown that these baboons display high level of social interaction that is based on mutual respect and kinship.

Even though baboon behavior has been studied extensively, biologists haven't been able to explain the mass hysteria in the baboons at the zoo.

"What frightened them? We don't know, it's a mystery. There have been many suggestions - an earthquake, escaped snakes, aliens, thunder," Wijbren Landman, a biologist at the zoo told told BBC News.

Landman said that the mass hysteria only affected the hamadryas baboons, the other animals- lemurs, elephants and kangaroos- haven't shown any sign of panic.