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N°33 I quarterly I APRIL 2014 In Images | 29 w BY Laure Cailloce The “hunt,” so to speak, is on. The Mandrillus project team, who has left its research station located in Bakoumba (Southern Gabon) a few kilometers away, parks its jeep at the edge of the forest in Lékédi Park. It’s just before sunrise, on an April morning in 2013. Anesthetic darts and blowpipes are prepared for catching the mandrills, together with syringes, scales, a portable ultrasound, and a host of other essential equipment. Everything needs to be ready before the mandrills come down from the trees. Once awake, these primates, endemic to central Africa, quickly move to other parts of the equatorial forest. Losing sight of them in such a dense environment would mean hours of tracking to find their trail again. The researchers know only too well: day in, day out, from dawn to dusk, they have spent the past 18 months monitoring a group of about a hundred individuals. It is the first time that such a population has been studied in the wild, and the scientists are anxious to have some of their many questions answered: how is the group structured? What are the determinants of the relationships between individuals? Does a mandrill’s health depend on the strength or quality of its social network? How do individuals behave toward parasitized conspecifics? “While our capture campaigns provide valuable information on the morphology and health status of each individual, 90% of our work consists of behavioral observation,” explains Marie Charpentier, behavioral ecologist at the CEFE,1 who founded this long-term project in early 2012. If, in the first months of the study, the scientists were only able to recognize about 20 of the mandrills, they can now identify 75 with the naked eye. “We look at which individuals stay together, groom or defend each other from aggressive third parties,” explains the researcher. “Automated data will also be available soon, as the mandrills are being fitted with radio-transmitter collars to record which group Lékédi park 01 Number 33, a non-dominant male, is the females’ favorite in the mandrill group studied. 02 03 Recruited by Marie Charpentier (with the binoculars) in the town of Bakoumba, these field assistants observe the mandrills every day. One of them uses a GPS antenna to locate three females fitted with radio collars. 04 05 Social relationships between the individuals in the group, such as the behavior of these females with their young, are under constant study. 06 The animals are knocked unconscious with anesthetic darts. 07 08 Ultrasound can measure the thickness of the mandrills’ intercostal muscles. 09 Once all the mandrills are fitted with radio collars, the researchers will be able to know which individuals are close to one another. 10 Male mandrill canines can measure up to 5 centimeters. 04 05 06 10 07 © photos : C. DELHAYE/CNRS Photothèque 08 09


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