Baraza

Category: wildlife | Date: Jul 24 2008 | By: Maina

I read about the re-introduction of five cheetahs into the wild at the Cheetah Conservation Fund blog and it reminded me of an article I had read in the Conservation magazine of the Society for Conservation Biology (Vol 9 No.1, Jan-Mar 2008). This particular article took me on a journey of the Lago (Lake) Guri archipelago in east-central Venezuela. For the record, the Lago Guri is the result of the construction of a mammoth hydroelectric dam at the confluence of the Orinoco and Caroní rivers in 1986 and the resultant flooding upstream. The Lago Guri has an expansive matrix of hilltop islands some as little as half-an-acre to 700-ha tracts of land.

So how does this tie in with predators? Simple, in the article, written by William Stolzenburd, one ecologist, John Terborgh, had come up with the theory that top predators were “the irreplaceable forces holding everything together”. Terborgh was not convinced that the modern extinction crisis was as a result of habitats shrinking or their fragmentation. He had observed that in the absence of top predators, the prey would “run amok, with cascades of local extinctions and ecological convulsions in their wake”. Terborgh had boldly declared this theory to his peers in his 1988 essay titled “The Big Things That Run the World” but he so badly needed to prove it.

When he learned of the Lago Guri in 1990, he found what he wanted: a place with islands small enough not to support any large predators. He started his experiment in 1993, by which time, the surviving species at Guri had ballooned to scary proportions. The resident howler monkeys for example, finding themselves without their natural predators, had multiplied and browsed their favorite trees bare. Now they were starving. The trees were fighting back by producing leaves with high concentrations of toxins but the monkeys were too hungry to notice. They would eat only to vomit a few minutes later.

Terborgh was advancing towards proving his theory, and, in a disturbing light, disapproving the island biogeography theory which calculates a ratio to the effect that the smaller and more isolated the island (or forest patch, etc.) the smaller the number of species it can support. According to this theory - proposed by Robert H MacArthur and Edward O Wilson way back in 1963 - fragmentation is the main culprit of extinction and biodiversity loss.

Now, my friend Dino introduced me to the writings of Edward O Wilson and, needless to say, I find Wilson very convincing. But if Terbogh is right, then we, the conservation conscious (and students of Wilson), must then start rethinking how we treat predators. As a matter of fact, we might have to rethink conservation all together.

While am not saying that Terborgh is right and Wilson is wrong (after almost half-a-century), all i am saying is that every species has its place in the whole scheme. Ecosystems are complex. For instance, the reason why there are no predators in the monkeys territory that i spoke of above is because the island is too small to harbor a large predator that can control the population of the monkeys. Therefore, fragmentation led to the absence of predators and the entire system is now collapsing.

Still, the role of the predator is important, and the recent introduction of these five cats into the wild by CCF could help the NamibRand Nature Reserve where they were re-introduced. It would be interesting to find out how these cheetahs fare and how the ecosystem health is affected.

Finally, I need to commend all our bloggers who are working with predators and to encourage them to take good care of our predators. If Terborgh is right, you will have saved the wild as we know it.

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Tags: cheetahs, conservation, ecology, howler monkeys, predators