By Kerri Miller
Reporter, Crossing Continents
Serengeti lions are vulnerable to human problems pressing up against the borders of the park
Almost half of Africa's lions live in just one country: Tanzania. But lions and humans are increasingly coming into conflict.
Lions have been known to kill up to 100 Tanzanian people in one year, and steal a much greater number of livestock.
An American lion researcher says the way to save lions is to focus on human poverty.
We met Craig Packer in Dar es Salaam, a noisy city on the Indian Ocean, Tanzania's historic capital.
He has spent seven months knocking on doors of politicians and foundations.
He is here on a mission for the Serengeti Lions he has spent 30 years studying
He wants to use the tools of science - data collection and analysis - to help poor Tanzanians improve their way of life.
"When I first came out [to the Serengeti], it was like being in some sort of fairy tale. There were no people. Things were like they were some misty time ago."
The Serengeti Lion project is one of the most ambitious carnivore studies in the world, spanning over 40 years
Packer threw himself into compiling detailed life histories of hundreds of lions.
"Over their whole lifetime, when they started breeding, when their cubs were born, how many, each time they gave birth, and how well their cubs survived."
The point was to build a record for the ages, of a species in undisturbed natural splendour.
But Packer discovered the Serengeti was not immune to the problems outside its borders.
In 1994, a third of the Serengeti lions died from canine distemper.
The disease had come from unvaccinated dogs that belonged to people living on the edges of the national park.
Packer helped vaccinate fifty thousand dogs living along the perimeter, and saw the collision course humans and lions were on.
"Hungry mouths or hungry families. Their dogs. Their need for land," says Packer. "Everything is just pressing right up against the edges."
Lions were leaving Tanzania's many national parks and hunting areas and preying on humans and their livestock.
Packer suspects the cause is ecological.
"If you are unable to live inside one of these well-protected national parks and find enough of the food you grew up eating - wildebeest, zebra, buffalo - then you are not going to stand there and starve while you watch a bunch of kids playing."
Villagers have set up a number of defences to protect their goats and cattle from attacks by lions
In Mkuranga, a village less than an hour's drive south of Dar es Salaam, two children were eaten by lions in 2007.
Packer notes that in the wild, lions prey on mature animals and eat them at the scene of the kill.
As the top predator, they have no one to fear.
But when they prey on humans or livestock, angry villagers chase after them sometimes killing a whole pride.
Lions have learned to take smaller prey they can carry away to eat.
Packer wants to learn what turns some lions into man-eaters and what villagers can do to better protect themselves and their animals.
The fewer lion attacks that occur, he reasons, the fewer revenge killings by villagers.
Packer wants rural people to see how their choices affect the environment around them.
"When you wake up in your rural village, where do you go to work? And I want to know how that decision affects where the wildebeest is going to graze. And what is the impact on children's growth? It is all linked, you can not look at it in isolation."
Savannas Forever have been surveying villages about their conflicts with wildlife
Packer and his wife launched an organization called "Savannas Forever" to provide practical solutions for protecting wildlife while reducing poverty.
They hired a team of Tanzanian graduate students to survey rural villages about their conflicts with wildlife, the trees they chop for firewood, and public health.
They weigh babies to find critical clues about what a village is eating. Are they relying on bush meat and competing with the lions for food?
But Packer's thinking has not made him popular.
One of the first things Savannas Forever did was to reach out to Tanzania's safari hunters, publishing a booklet with them to help identify which older male lions to shoot.
Packer sees hunting as an important way to keep the population in check so lions do not terrorize the local people.
This put him out of step with conservationists, but Packer does not consider himself "a bunny hugger."
"I grew up in Texas," he says, "I grew up hunting. I am perfectly all right with hunting. It can be a valuable tool for conservation but only if it is regulated."
But as Packer dug deeper into the hunting industry's wildlife management practices, they grew wary.
Charles Buekes is a professional hunter who originally supported Packer's work.
"He started wanting to do a little bit more than he actually told us," explains Buekes, "and started stepping on people's feet, other NGO's toes, ... and he basically overextended himself."
Buekes mentions AIDS research as an example of how Savannas Forever is expanding its reach. To Packer, it is part of understanding the web of human misery that takes its toll on the environment.
To his opponents, he has strayed far beyond his expertise as a lion researcher.
Neither the hunting companies nor the government will reveal how many lions are taken by trophy hunters each year, and Packer suspects the lion population is crashing.
The government drastically raised hunting fees this year to raise more revenue. We wanted to talk with the wildlife division but they declined repeated requests for an interview.
For the time being, the Tanzanian government has blocked Packer's Savannas Forever team from doing any more village surveys. A new law has gone into effect giving the wildlife division control over all research - on animals or people - in rural areas.
Packer can still study his Serengeti lions, but he says that feels self-indulgent.
"I knew too much to be able to live with myself in that self-indulgent mode. There were things I had to deal with directly and nobody else would do it."
But Packer admits he has grown weary of the battles.
"All I really wanted to do was focus people's attention on what the problems are."
He does not talk about giving up, despite being in debt and having made powerful enemies.
"All these wildlife populations we have been looking at - none of them are safe and the livelihoods of these people are not secure and I do not see that anybody is really prepared or capable of making the difference that is necessary. It is just so large."
Crossing Continents on BBC Radio 4 reports from Tanzania on the uneasy co-existence of man and lion on Thursday, December 27 at 1100 GMT.
This episode is a co-production between American Public Media and the BBC