Do Elephants Affect Frogs?

Elephants are hefty herbivores that are well known for their 'destructive' feeding behaviour. This has been demonstrated throughout Africa and said to change the look of the bushveld landscape.

But how does this affect the smaller creatures further along the food chain? This is a question that is being tackled by an ambitious research program led by the Organisation for Tropical Studies (OTS), who are currently working in the Kruger National Park (KNP).

This is part of a broader research program run by Sanparks Scientific Services, which looks at the impact of elephants on biodiversity. The focus of this particular study is to look at different frog communities in vegetation of different areas along the Sabie River.

The idea behind this is to see if areas with shorter vegetation and more open areas have different species of frogs living there compared to those sections of the river which have tall trees and a closed canopy.

To see what goes hopping about in these areas, the team set out a series of four pitfall traps in five places with tall tree and five places with only shrubs and these were checked everyday.

Fortunately KNP experienced some welcome early rain and this seemed to get the frogs out and about. "We collected 11 frog species during the survey" explained Dr Laurence Kruger from OTS "but it seems the frogs were enjoying the cooler wet weather and we caught lots of individuals of the same species.

We also had other smaller creatures in the traps including scorpions, spiders, a few snakes and even skinks, which makes it interesting every time we check the traps. You are never sure of what you are going to find” explained Laurence.

This initial survey found that there were equal numbers of frogs in both sample sites but of all the species collected, three species were only found in the sites with tall trees.

So even though it seems that frogs are happy to move about in all areas, some species do have specific habitat requirements, in this case they prefer areas with tall trees.

If these trees are lost from the ecosystem, it could be detrimental to these habitat specific species. This is the first of many such surveys, which are done in conjunction with bird and small mammal surveys, throughout the KNP.

It will be interesting to see how these trends differ in different landscapes of the park. All the frogs collected are taken back to the lab where they are correctly identified, photographed, weighed and returned to place they were collected from the next day.

Frogs were selected for this survey as global scientific research has shown that they are good indicators of how healthy an ecosystem is and if there is a problem, they are often absent or in lower numbers. This has been shown to be true in areas that are highly polluted.

Frogs are very sensitive to habitat change and if elephants are having an effect on their environment, surveys such as this will be able to determine if this is actually happening and how serious the problem is.

Information collected during these surveys is valuable for scientists and park managers who have the difficult task of looking after all aspects of biodiversity from the smallest frog to the biggest elephant and everything in between.

Text and images by Michele Hofmeyer

Kruger National Park - South African Safari