Figure from Pastorini et al. 2010 - A 'rare' daytime visit to a reservoir by a male elephant.

Water is something that all living things require, to varying degrees.  Elephants require a great deal.  Researchers in Southern Sri Lanka from the Center for Conservation Research have recently found that this dependence on water may be the key to determining whether elephants inhabit an area [1].

One may not think of elephants as being particularly difficult to spot, but in the scrubby or dense habitats most Asian elephants occupy, they can be surprisingly shy and reclusive.  In fact, it has been our own experience that it is nearly impossible to view elephants outside of national parks. Herds, which contain vulnerable calves, are particularly cautious, preferring to remain hidden throughout the day and coming out only at night.  This makes Asian elephants very difficult to count, and is part of the reason we have such a poor idea of how many there are in the wild.

But elephants do leave indirect evidence, by way of footprints and dung.  And in areas where water is scarce, or available only during certain times of year, any elephant within walking distance is bound to turn up and make use of it.  By looking for these indirect signs, we can get a rough idea of their space use.  It wouldn’t tell us how many there are, but it would simply indicate their presence or absence from a location.

Researchers find that perennial tanks (i.e. those that reliably contain water most of the time) are more popular with elephants, particularly herds with young.  Interestingly, while the presence of temporary huts discouraged  elephants from using a water source, the presence of permanent buildings did not.  One might guess that this is because they become habituated over time to whatever activity is present and learn to time their visits accordingly.  There was also some suggestion that the size of the water body may also matter, with elephants possibly preferring larger ones to smaller ones.

A finding particularly relevant to conservation and wildlife management is that in areas thought to be evacuated in the past through the use of ‘elephant drives’ in fact still do contain elephants.  The authors suggest that the drives may even lead to more conflict by making the elephants accustomed to disturbance.

The authors suggest that surveying areas around water bodies may be a cost-effective way of determining whether and how elephants make use of habitats, providing much-needed data on which to base human activities and management measures.  A recently announced census plan by the Department of Wildlife Conservation suggests that someone is taking this advice into consideration.

The creation of artificial water sources by people (i.e. reservoirs, or ‘tanks’ as they are called in Sri Lanka) is a common practice, both for human use and what has been termed ‘habitat enrichment’ for wildlife.  However the effect of this both on elephants and surrounding habitats is mixed [2].  In parts of Africa where this has been done (particularly in the middle of forest patches), there are sometimes adverse effects on surrounding landscapes.  Elephant populations that may previously have passed through an area, allowing trees to recover from their browsing, may linger for longer periods of time and cause more severe damage to trees as a result.  Moreover, water sources close to human habitation can become attractants that promote conflict.  Therefore while water sources offer a feasible means of detecting elephants, their effects and placement for this very reason should be very carefully considered.

[1]Pastorini,J., Nishantha, H.G., Janaka, H.K., Isler, K., & Fernando, P. (2010). Jennifer Pastorini, H.G. Nishantha, H.K. Janaka, Karin Isler, & Prithiviraj Fernando (2010). Water-body use by Asian elephants. in Southern Sri Lanka Tropical Conservation Science, 3 (4), 412-422. Article

[2] Loarie, S., Aarde, R., & Pimm, S. (2009). Fences and artificial water affect African savannah elephant movement patterns Biological Conservation, 142 (12), 3086-3098 DOI: 10.1016/j.biocon.2009.08.008