Why do animals dig waterholes?

Animals digging waterholes in Ruaha National Park (Tanzania). Photo: Claudia Stommel
Animals digging waterholes in Ruaha National Park (Tanzania). Photo: Claudia Stommel
Scientists from Berlin showed that animals in the Ruaha National Park in Tanzania, East Africa, already dig waterholes during dry seasons even if water is still available in the riverbed. When the river dries up and the water stops flowing, the water quality in the remaining pools deteriorates as they are contaminated with faeces and bacteria. In order to gain clean drinking water the animals have to find new water sources. The study has been published in the scientific journal „Mammalian Biology“.
 
Researchers from the German Leibniz Institute for Zoo and Wildlife Research (IZW) examined the relation between the digging of waterholes by wild animals and the availability and quality of water in the Ruaha National Park in Central Tanzania. With its National Park and its adjacent sanctuaries, the Ruaha ecosystem covers 50,000 km² of the miombo woodlands in Eastern and Southern Africa. The observations took place along the Great Ruaha River during three dry seasons from June to November 2011 to 2013. They clearly demonstrated that wild animals not only dig waterholes when the river is completely dried up but already when the river stops flowing. The water in the remaining pools was highly contaminated by bacteria and faeces.
 
The scientists conducted the research along a 130 km stretch of the river. They were able to observe elephants, plains zebras, warthogs and yellow baboons digging waterholes. Other species also drank from these holes. The waterholes were used for up to two weeks. Sometimes they were the only available water source within a radius of five kilometres. The waterholes may enable some species to stay in areas they otherwise would have to leave during dry seasons.
Water is essential for life, which is why animals in the Ruaha National Park have to adapt in times of water shortage. The results indicate that digging waterholes is such an adaptation. By digging waterholes, wild animals probably reduce the risk of infections which is more likely with the ingestion of potential pathogens. Many germs including bacteria use water as a transmission path between different hosts.
 
The results emphasise the essential role of the Great Ruaha River as a key water source for wild animals in the Ruaha ecosystem during dry periods. The deterioration of the water quality during dry season is on the one hand ascribed to the stagnation of the river; contaminations cannot drain off. On the other hand, remaining pools get contaminated with faeces and urine as they are highly frequented by wild animals. It is therefore important to maintain the water flow throughout dry seasons. Since the 1990s the Great Ruaha River has stopped flowing and dried out inside the National Park for a period of up to three months during dry seasons because its water has been used upstream of the National Park on a large-scale basis for agriculture.
 
Publication:
Stommel C, Hofer H, Grobbel M, East ML (2015): Large mammals in Ruaha National Park, Tanzania, dig for water when water stops flowing and water bacterial load increases. MAMM BIOL; doi:10.1016/j.mambio.2015.08.005
 
Contact:
Leibniz Institute for Zoo and Wildlife Research (IZW)
Alfred-Kowalke-Str. 17
10315 Berlin
Germany
 
Marion East
Phone: +49 30 5168-512
 
Steven Seet
Phone: +49 30 5168-125

 

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Background information:
 
The Leibniz Institute for Zoo and Wildlife Research (IZW) investigates the vitality and adaptability of wildlife populations in mammalian and avian species of outstanding ecological interest that face anthropogenic challenges. It studies the adaptive value of traits in the life cycle of wildlife, wildlife diseases and clarifies the biological basis and development of methods for the protection of threatened species. Such knowledge is a precondition for a scientifically based approach to conservation and for the development of concepts for the ecologically sustainable use of natural resources. The IZW belongs to the Forschungsverbund Berlin e.V. (www.fv-berlin.de)

www.izw-berlin.de

Evidence is increasing that water may have been overlooked as a path of transmission of pathogens. It is assumed that pathogens shed into water bodies gain a fitness advantage under optimal ecological settings by evolving traits permitting both the retention of their infectivity in water and a reduction of host specificity. The IZW is also a member of the Leibniz Research Alliance “Infections‘ 21“ to combat infectious diseases in the 21st Century. Within the alliance, the IZW examines water as an aquatic viral vector for new emerging diseases (research project “AQUAVIR”).

 

The Leibniz Association connects 89 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services. The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz Institutes collaborate intensively with universities – in the form of “WissenschaftsCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad. They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the institutes’ importance for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 17,500 individuals, including 8,800 researchers. The entire budget of all the institutes is approximately 1.5 billion EUR.

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