South African reserves facing unprecedented elephant populations could turn to immunocontraception to slow growth
?| December 22, 2011?|
Too Many Elephants Elephants in Addo Elephant National Park, in South Africa, gather around the watering hole.
Image: Clive Reid, Flickr
In South Africa they have a problem, a big one: too many elephants.
For most of the 1900s extensive poaching threatened to wipe out the country?s elephants. In response, conservationists established reserves throughout the region and relocated as many herds as they could. Now those herds are doing quite well. So well, in fact, that they?re causing problems. Wildlife managers are currently facing a dilemma: how to deal with too many elephants. While some advocate for culling the giants, a group of scientists has outlined a different plan to control their populations: contraception.
Rather than simply setting a quota and culling the extras, immunocontraception could be a tool to allow land managers to control elephant populations in response to conditions on the ground such as food availability. "The approach now has to be much more dynamic and look at the influence the animals are having on the land," says Robert Slotow, a biologist at the Amarula Elephant Research Program in Durban, South Africa. His team recently published a paper in PLoS ONE describing how scientists might be able to use immunocontraception?a vaccine that gets the body to make antibodies that target sperm receptors on the surface of the egg cell. Slotow and his team outlined an immunocontraception schedule that would halt the growth of herds in a South African park and even out their population structure.
The problem
In the wild, two things control elephant populations: natural mortality and environmental conditions. Calves and full-grown animals get sick and die from all kinds of things, from predation to viruses. And when the environment is unfavorable?during years of drought or food shortages, for instance?females will put off having babies. In closed systems like conservation parks, however, neither of those controls is in place. The fences around the park keep out new animals and pathogens, and controlled park conditions make sure that there is ample food. Mothers keep having babies, and the death rate seems to slow to a crawl.
But simply letting the population boom isn?t an option either. Herds can reduce forests to grasslands by trampling plants and uprooting trees as they feed. There is concern that the elephants are pushing out other species. Kruger National Park, the oldest elephant reserve in South Africa, has about 15,000 elephants. The sustainable number estimated for the park is probably more like 7,500. One way that Kruger dealt with its growing population was to relocate juveniles to other parks in South Africa, which temporarily solved the problem in Kruger but created issues elsewhere. These smaller parks suddenly had a bunch of elephants that were all the same age, which leads to a young, fast-growing population. Now those smaller parks are having the same challenge?too many elephants.
In 2008 South Africa announced it would lift the 1994 ban on elephant culling to deal with increasing populations, although to date the cull has not happened. Culling itself is controversial: some argue it?s a way to utilize a resource and profit from the skin, meat and ivory provided by elephants, whereas others contend that the killing is barbaric and unnecessary.
?All these things that people want to talk about?deer gnawing on your shrubbery, culling elephants?they?re symptoms of the larger problem, which is reproduction,? says Jay Kirkpatrick, director of the Science and Conservation Center at ZooMontana and longtime advocate for immunocontracpetion. And if you want to curb reproduction, he says, contraception is one option.
A potential solution
Source: http://rss.sciam.com/click.phdo?i=37598193f90bc4be1f36fb6fbdc1373b
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