By Daniel Dickinson BBC News, Dar es Salaam

This lion is believed to be one of the biggest killers of humans

They say the lion probably switched from hunting buffalo to humans because it found the meat less painful to chew.

The lion stalked its prey in eight villages in the coastal Rufiji River district over a period of 20 months.

It was finally killed by game scouts in April 2004, around 150km south of the commercial capital Dar es Salaam.

Man-eating lions are not unheard of in Tanzania.

Around 200 people are killed by wild animals each year in Tanzania, a third of those by lions.

It almost certainly found humans easier to catch and less painful to eat Dr Rolf Baldus GTZ wildlife programme coordinator

What makes the story of this latest man-eating lion so shocking is its profligacy.

It is probably the highest number of deaths ever recorded for one lion.

Since the lion was killed, wildlife researchers have been trying to determine what drove it to kill so many.

Large abscess

And now they have come up with an intriguing theory - that the lion had been suffering from toothache.

When the skull of the lion was examined, a large abscess was discovered under one of its molar teeth, which was cracked into many pieces.

Tanzania is believed to have the highest number of lions in Africa

"This lion probably experienced a lot of pain, particularly when it was chewing," said Rolf Baldus, coordinator of the wildlife programme of GTZ, the German development cooperation agency which has been working with the Tanzanian government on wildlife conservation issues for the past 17 years.

"It probably gave up hunting wild animals like buffalo because the meat was just too tough and too painful to chew. It almost certainly found humans easier to catch and less painful to eat."

There is of course no scientific proof for the toothache theory.

One of the main problems facing scientists researching the behaviour of man-eating lions is that the lions themselves are seldom caught and so analysis is extremely rare.

Taught to hunt

One fact that many lion authorities do agree on, however, is that it is not just old lions who are unable to hunt effectively who turn into man-eaters.

The Rufiji lion was just three and a half years old - a young adult.

"This lion was probably taught to hunt humans by its mother when it was young. Perhaps it gave up hunting humans until it got toothache but then restarted," Mr Baldus said.

Tests revealed a large abscess behind one of the molar teeth

The lion population in Tanzania, it is thought, is the highest in Africa.

This is partly due to the large areas of wilderness lions can roam in but also the Tanzanian government's policy of protecting them and managing them sustainably through controlled hunting.

Most attacks on humans have taken place in the south of the country. It is a trend which experts are yet to fully understand.

The capture and shooting of the Rufiji River lion does not of course mean that attacks against humans will stop in the district.

Its death has however, according to Dr Baldus, put the conservation of lions and the relationship with local people back on the agenda.

"Care must be taken that rural people benefit more from the wildlife they live alongside. This will serve as a powerful incentive to tolerate and even conserve them."