Elephants on a tight-rope

“Eastern Serengeti 2012 06 01”- Savanna elephants

I spent the last week looking through lots of documents on elephants (even a few theses, so there was a mountain of reading), and I’ve learned quite a bit about what elephants eat, how populations have changed, and the impact that these mega-herbivores can have on the environment around them- they definitely live on a large scale. Some of the big ideas I gleaned from my elephant reading are:

  • These animals eat a lot of food, they pull off bark, and they even knock down trees (Coetzee et al. 1979), and their diet is very adaptable (Steyn 2003).
  • Elephant ranges have become increasingly restricted, partly through conversion of land for agriculture and development, and partly because elephants are confined to specific areas (like parks) by fences (Cumming et al. 1997).
  • When talking about elephants in Africa, it’s important to differentiate between savanna elephants (Loxodonta africana) and forest elephants (Loxodonta cyclotis)- they interact with their environment in diverse ways (Blake 2002).


Elephant populations around the world have fluctuated– for example the ranges of savanna elephants have contracted over 75% since AD 1500 (Morrison et al. 2007), and the elephant population of the Eastern Cape of South Africa had been nearly destroyed by 1931,  but by 2001 there were over 400 animals (Boshoff et al. 2002). As a result of these changes in elephant ranges and numbers, we’re still figuring out how elephants fit into ecosystems. And since both elephants and some plants (such as trees) can live for a long time, it may be decades before we fully understand all the pieces of the puzzle- imagine trying to study the environmental impact of an animal that lives 60-70 years, especially when it has been reintroduced to a location in the last decade. We do know that elephants eat a wide variety of foods and that their food preferences may change from season to season, and elephants do more than just eat- they remove plants, make trails, and even create watering holes (Steyn 2003).


Forest elephants vs. savanna elephants. These two species can have very different effects on the world around them- both create paths between resources, but forest elephants eat more fruit while savanna elephants eat more grasses. Since only some trees are fruiting at a particular time (versus grass which is usually available over longer periods of time), it’s important to remember where they are at the right moment, and trails can help elephants in that regard- paths around fruit tree patches tend to be bigger (Blake & Inkamba-Nkulu 2004) perhaps as a way to lead elephants to those resources. These trails operate as highways for other species, giving them access to areas they may not otherwise have reached. Forest elephants also help disperse seeds from fruiting plants and can move them great distances. Why is this important? Apart from helping the plants spread to new locations (an estimated 3192 seeds/elephant/day!), some of the plants are used as economic resources by people (Dudley 2000).

By stripping bark off the trunk, elephants can injure or even kill the tree

Savanna elephants are involved in the transformation of woodland and thickets into grassland (although not the only factors and I saw many, many differing estimates of how important elephants are)- by pulling down trees and breaking tree trunks, they can open up areas for colonization by grass, which is helpful for some species such as zebra (Steyn 2003)- of course, that can be a problem for animals like giraffes which browse on woody vegetation (Chafota 1998). Why is this important? If you’re trying to manage a reserve or park, your decisions are made more complicated when a species both helps and harms others.


So why did I put elephants on a tight-rope? To a large degree, keeping elephants and ecosystems healthy seems to be about balance: balance between space and population density, and balance between competing interests. As a result of restrictions in movement caused by park fences plus growing populations, elephant densities in some areas have reached unnaturally high levels (Cumming et al. 1997)- those crowded elephants have no place to go and all depend on the same resources, which can lead to habitat degradation, as in Amboseli National Park where bushbuck and lesser kudu disappeared due to elephant-caused changes in the ecosystem. At the same time, too few elephants can have an equally negative impact on some species- in Hluhluwe Game Reserve, zebra and wildebeest declined after extermination of elephants helped forests and thickets spread (Chafota 1998). Transition from woodland to grassland is helpful for grazers, but not necessarily for browsers- how do you maintain enough of each habitat? Tourists want to see elephants- it’s easier to see find elephants when they exist at higher densities, but that could mean declines in other animals such as black rhinos. It’s all about finding the pivot point.


So there are many ways in which elephants interact with what is around them, and, in some cases, researchers are finding newer ways of measuring those interactions. The amount of disagreement about elephant impacts I found in this background reading surprised me, although I guess I should expect such a massive animal to be the subject of a wide range of opinions. For next week, I’m going to look at more current research and also take a peek at how these issues connect to large herbivores in other locations. There are so many facets to this topic and I don’t expect to touch upon them all- given the complex nature of elephant ecology, there may be no single lesson to take away from this, but I imagine that it’s going to be pretty fascinating no matter what I uncover in this information mega-transect.


Works Cited:

Blake, S. 2002. The ecology of forest elephant distribution and its implications for conservation. PhD dissertation, University of Edinburgh.

Blake, S. and C. Inkamba-Nkulu. 2004. Fruit, minerals, and forest elephant trails: do all roads lead to Rome? Biotropica 36(6): 392-401.

Boshoff, A., Skead, J., and G. Kerley. 2002. Elephants in the broader Eastern Cape- an historical overview.  In Kerley, G., Wilson, S., and A. Massey, eds. “Elephant Conservation and Management in the Eastern Cape: Proceedings of a Workshop Held at the University of Port Elizabeth.” Terrestrial Ecology Research Unit: Port Elizabeth, South Africa.

Chafota, J. 1998. Effects of changes in elephant densities on the environment and other species- how much do we know? From “Proceedings from the Workshop on Cooperative Regional Wildlife Managements in Southern Africa” University of California, Davis, August 13-14, 1998.

Coetzee, B.J.,Engelbrecht, A.H., Joubert, C.J., and P.F. Retief. 1979. Elephant impact on Sclerocarya caffra trees in Acacia nigrescens tropical plains thornveld of the Kruger National Park. Koedoe 22: 39-60.

Cumming, D.H.M, Fenton, M.B., Rautenbach, I.L., Taylor, R.D., Cumming G.S., Cumming, M.S., Dunlop, J.M., Ford, G.S., Hovorka, M.D., Johnston, D.S., Kalcounis, M.C., Mahlanga, Z., and C.V. Portfors. 1997. Elephants, woodlands and biodiversity in miombo woodland in southern Africa. South African Journal of Science 93: 231-236.

Dudley, J.P. 2000. Seed dispersal by elephants in semiarid woodland habitats of Hwange National Park, Zimbabwe. Biotropica 32(3): 556-561.

Morrison, J.C., Sechrest, W., Dinerstein, E., WIlcove, D.S., and J.F. Lamoreux. 2007. Persistence of large mammal faunas as indicators of global human impacts. Journal of Mammalogy 88(6): 1363-1380.

Steyn, A. 2003. The impact of introduced elephant on selected woody plant species on the Songimvelo Game Reserve. Dissertation, Technikon Pretoria.