IWRA Proceedings

AbstractIntroduction. Surface water is an essential source of life for mammals and higher vertebrates. Global warming and dryness restrict available water resources. In the African Sudanese climate, an annual rainfall deficit period, up to 350mm, began in the 1970’. Objective. How do Chimpanzees living in dry habitats face increasing dryness as water pools dry at the end of the dry season? Methods. In 1975, 1976, and from 1988 to 1999, we followed groups of chimpanzees and baboons living inside and outside the Niokolo Koba national Park in the Kédougou department, Senegal, and recorded water related behaviors and indices. Additionally, comparative blind tests of water samples drink ability were made. Results. In contrast with the 1975-1994 surveys, those carried in the 1995-1999 period revealed that chimpanzees and baboons dig wells in river basins during the dry season. The wells are hand dug holes of 20 to 40 cm depth, localized in fine sand zones less than 2m far from stagnant water puddles. The water in the wells is therefore filtrated by the surrounding sand. Indices of animals access to water were only found around the wells dug in the sand, not near the stagnant water puddles. The water of the wells was clear and limpid, contrasting with the stagnant water of the natural puddles. Some wells dug by chimpanzees were dug with wood sticks used as “tools”. Results of comparative bacteriological analyses show that pathogenic germs characteristic of stagnant putrid water were present in the natural puddle water and made water unsuitable for consumption, but were absent in the wells. The water of the wells contained only pathogenic germs typical of mammal species which came to drink there, indicating that the chimpanzees have contaminated the water with their own germs. Discussion. Some mammal species like warthogs and antelopes dig for water in the bottom of dried pools as the water vanishes in the dry season. Although water is still available as stagnant putrid water pools, chimpanzees and baboons dig holes in the sand nearby the stagnant water pools and get clear, limpid, filtrated water without pathogenic germs, except for germs that probably came from the primates themselves. Conclusion. Among the Chimpanzees populations studied on the long term in Africa, the Senegalese one lives in a very hot and dry habitat and is the first one recorded, in 1995, to filtrate water. This behaviour has then been observed in other sites like in Uganda, were it has been recorded from 1997. Digging wells in order to get filtrated water is a new cultural behavior. It appeared recently independently in different Chimpanzees populations, as an adaptation to face a long increase of dryness period. Acknowledgements. National Parks of Sénégal. Grants ORSTOM, IRD, DDR.