A growing number of people in Tanzania are being attacked by lions, resulting in the killing of these endangered animals. Wildlife researchers discuss the problem this week in the journal Nature.
In the past decade, there has been an upward trend in Tanzania in the number of rural people being killed by lions, according to Craig Packer, a professor at the Department of Ecology, Evolution and Behavior at the University of Minnesota.
"In the early 1990's, there might be an average of 30 or 40 cases per year, and now we are well above a hundred," he said. "And we think that ultimately this has to do with the fact that the human population in Tanzania has grown so much that there just far fewer resources for the wild lions that live outside the [conservation] parks."
The country's population has grown rapidly, from 23 million in 1988 to more than 34 million in 2002. Mr. Packer says this has reduced the amount of land and natural prey that is available to lions in the wild.
In the study reported in Nature, Mr. Packer and colleagues looked at the distribution of man-eating attacks, which appear to occur most often during the harvest period between March and May. An analysis showed that half of the attacks occurred in four districts in southern Tanzania, between the capitol, Dar es Salaam, to the border with Mozambique.
Mr. Packer says in those areas there is very little natural prey for the lions, but heavy populations of bushpigs, animals that are crop pests.
Mr. Packer says the bushpigs pillage the crops at night. So, it is common for farmers wanting to protect their fields to sleep in them. Unfortunately, that puts them at risk for being attacked by lions.
"Once the lions learn that they can take human flesh for food, they can become very aggressive and they can become very adventurous," he explained. "And instead of just taking victims from agricultural fields, they will actually go into villages; they will break into peoples' houses; they will pull people out of bed."
Once there has been an attack, lions are often hunted down and killed.
Tanzania has the largest number of lions in the world, and researchers propose protecting some of the country's dwindling population of 12,000 cats by keeping bushpigs away from crops.
One strategy includes protecting fields by digging ditches that the bushpigs cannot cross.
Another possibility - planting a fenced crop just for the pigs.
"And the pigs learn that they can go into this, and they have free access to this field. It is sort of the pigs' field," Mr. Packer said. "And as time goes on, as the pigs get more and more used to being able to going into their field, and your own crops are getting closer to maturity, one night you just wait until all the pigs are in the field and you go and close the gate on their fence. And you have trapped the entire population around there."
Researchers also note that people hunted by lions are usually alone, so they should try to stay together in groups.
The investigators say the safety and well-being of humans come first. But they conclude resolving the conflict between humans and lions must be a top priority if animal conservation efforts are to be successful.