image sourceGrace Ekpu/BBC

Bala Amarasekaran and his wife, Sharmila, spotted the baby chimpanzee tied to a tree in a village in a rural part of Sierra Leone.

He was for sale.

The couple bought the animal and pledged to care for him.

Little did they know that this chance encounter would change their lives. Three decades later, they run a sanctuary devoted to saving the critically endangered subspecies known as the Western chimpanzee.

"We didn't understand what we were getting into," Mr Amarasekaran says.

"We were newly married and we had this affection seeing this baby chimp and we thought: 'OK, we'd bring him home and nurse him.' That's all we thought about.

"But once he came into our lives, I think we got attached.

"We rescued another one and another until we had seven or eight chimps in our house and that is what drove us," he adds.

The Tacugama Chimpanzee Sanctuary the couple set up is now home to about 100 Western chimpanzees. It sits in a patch of pristine rainforest on the outskirts of the capital, Freetown.

image sourceGrace Ekpu/BBC

These primates mostly live in the forests of Sierra Leone, Guinea and Liberia. They are also found in Ivory Coast, Ghana, Guinea-Bissau, Mali and Senegal.

Western chimpanzees have been found to use tools unknown in other chimpanzee populations, a 2016 paper in the American Journal of Primatology said. These include cracking nuts, hunting bush babies with spears and throwing stones.

But they are under threat.

The population is estimated to have declined by 80% between 1990 and 2014, to about 52,800.

They mostly live in the wild. Only 17% of Western chimpanzees are to be found in protected areas.

image sourceGrace Ekpu/BBC

As urbanisation and development eat into their forest habitat, Western chimpanzees have been put "on a trajectory towards extinction unless drastic measures are taken" to protect them, according to the International Union for Conservation of Nature (IUCN).

In 2016, the organisation moved their status on its Red List of threatened species from being endangered to critically endangered, reflecting their increasingly dire situation.

image sourceGrace Ekpu/BBC

In 2019, Sierra Leone became the first country in the world to declare the primate a national animal, in a bid to reverse this trend.

"Sierra Leone has a significant population. Between Sierra Leone, Guinea and Liberia, we probably have 70% or 75% of these Western chimpanzees and if we do not address this issue, as three nations, we will watch them disappear right before our eyes," Mr Amarasekaran warns.

image sourceGrace Ekpu/BBC

The conservationist, who gave up his 15-year career as an accountant and has dedicated his life to the chimps, sees it as a sense of obligation.

"For every rescue, we try to do our best to make their lives different, because they have suffered at the hands of humans," he says.

Mr Amarasekaran feels he has a special connection with every chimp at the sanctuary and adds: "They still have that lifelong relationship with me and I think that will last forever."

The chimpanzees are also attached to the people who take care of them every day.

Among the chimpanzees at the sanctuary is Celia, a six-month-old orphaned baby. When she arrived at the sanctuary she could not sit or walk.

image sourceGrace Ekpu/BBC

Celia was rescued from the hands of poachers after having been burnt when people set fire to some land in order to clear it.

Posseh Kamara – also known as Mama P – is responsible for looking after her, including bottle-feeding her.

"I feel good every day when I wake up because I have to work with my baby chimps. I grew to have a love for the job and for the baby chimps," Mrs Kamara says.

image sourceGrace Ekpu/BBC

Most of the rescued chimpanzees arrive malnourished and abandoned, often traumatised after being separated from their group. They are then cared for and rehabilitated at Tacugama.

Mrs Kamara, who has grandchildren of her own, says it breaks her heart to see what the baby chimpanzees have to go through. She adds that she is proud of the progress she has made with Celia.

As the chimpanzees grow older, they are brought together with others and use an enclosure where they learn skills before being released to join the 100 others that now call this sanctuary their home.

image sourceGrace Ekpu/BBC

Tourists and local people, including children, spend time at the sanctuary to learn about the chimpanzees and wildlife in general.

Mr Amarasekaran says educating people about the risks facing the Western chimpanzees is essential, and the sanctuary is working with communities across Sierra Leone.

It has a growing international profile but for the founder it is most important to get the message across to people at home

"Sometimes you get [more] recognition from afar than from within," he says.

All pictures by Grace Ekpu