for National Geographic News
Cannonball!
Scientists have found that male gorillas in the
forests of northern Congo (Brazzaville) deliberately splash about in
swampland clearings to intimidate their competitors in the battle to woo
female companions.
The discovery is the first evidence of a wild
animal using its body to manipulate water for a visual effect.
"If you see a 160-kilogram (353-pound) silverback charging into the river, you are unlikely to lead to the conclusion that he is bathing," said Richard Parnell, a primate researcher at the University of Stirling, United Kingdom. "It is a very forceful display."
Parnell and his colleague Hannah Buchanan-Smith studied the behavior of western lowland gorillas at Mbeli Bai, a swampy clearing in the Congo where at least 14 gorilla families come to feed. The gorillas visit the area regularly to eat aquatic herbs, some of which are high in sodium.
The frequency of those visits makes the site a good place for researchers to observe the gorillas and study the interactions among families and individuals. Parnell and Buchanan-Smith monitored the gorillas' behavior over a 32-month period that ended in 1999.
The insight they acquired is especially intriguing because researchers have generally found it difficult to get close to western lowland gorillas in the dense forests of the Congo, so knowledge about their social behavior is quite limited.
Splish-Splash
From their observations at Mbeli Bai, the researchers discovered that the wide-open swampland was more than just a feeding ground. In human terms, an analogy might be a pick-up joint, like a hotdog stand at the beach on a hot summer day.
"The bai is a great place to check out females," said Parnell.
A male who's searching for a female companion might go the clearing to feed on the swampy vegetation but also to watch members of gorilla groups that stop by. What the solitary male gorilla appears to be hoping for, the researchers say, is an opportunity to hook up with a female.
To strengthen his chances of being the one chosen by a female, a male often intimidates other males by heartily displaying his splashing prowess. The behavior is so pronounced the researchers could observe it from a fairly long distance.
"We are pretty confident that the behavior is tied to aggressive display where [the male gorilla] is saying something about himself—announcing his presence and saying he is not to be messed with," said Parnell.
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