KIGALI, RWANDA — In 1988, a small group of almost-extinct mountain gorillas in volcano ranges straddling Rwanda, Uganda and the Democratic Republic of the Congo became movie stars.
Since then, not much has changed about the Rwandan parkland featured in “Gorillas in the Mist.” But a lot has changed for the gorillas.
No longer movie stars, mountain gorillas have more than tripled in population to more than 750, but their species remains one of the rarest on earth.
Tens of thousands of people, including Rwandan President Paul Kagame, plan to celebrate the growing population on Saturday.
Every year, Rwandans hold what feels like a national holiday called “Kwita Izina” - an adaptation of a traditional naming ceremony held especially for gorillas.
This year, 22 baby gorillas will be named - the largest batch since the event began seven years ago.
Planners say this year’s ceremony is especially happy because of the unusual births of two sets of twins since last year’s naming ceremony. Seven gorillas have given birth to twins since the animals started being monitored in the 1960s, but rarely do the offspring survive.
Rica Rwigamba, head of tourism and conservation at the Rwanda Development Board, said the four twins - three males and one female - appear to be doing fine, and two will be named at Saturday’s ceremony. The other two, born May 27, will be named at Kwita Izina 2012.
Ms. Rwigamba said gorillas have served as the mainstay of the country’s tourism industry, which caters to high-end, eco-friendly visitors and collected $200 million in 2010.
“Mountain gorillas [are] the anchor product that Rwanda is known for,” she said in the Rwandan capital, Kigali.
Mountain gorillas in Rwanda are treated like national heroes, accounting for 90 percent of the country’s tourism revenue.
Visitors pay $500 to see the gorillas, excluding the price of travel, food and lodging. Gorilla permits often sell out months in advance because any given family of gorillas in Rwanda is allowed a maximum of eight visitors a day.
Still, the gorillas live practically on top of some of the most crowded and poorest areas in the region, leaving the animals constantly vulnerable to encroachment, human diseases and poachers.
“It’s still a very, very delicate, small population,” said Dr. Mike Cranfield, executive director of the Mountain Gorilla Veterinary Project, an organization that has been providing health care to the gorillas since the mid-1980s. “There is no buffer zone around it.”
Known as one of the organization’s “gorilla doctors,” Dr. Cranfield said the gorilla population is growing rapidly and has increased by 26 percent in the past seven years.
Dr. Cranfield said gorilla safety and population growth remain matters of constant vigilance.
Most of the people who live around Volcanoes National Park, the Rwandan territory where the gorillas roam, live on about $1 a day, he said. The extreme poverty induces a tendency to exploit the forest for short-term gains, such as poaching and illegal animal trafficking, which could destroy the gorilla population.
“If you look at any conservation issue,” Dr. Cranfield said, “it seems to be magnified here to an extreme.”
Rwanda’s government has several programs designed to protect the forest, Ms. Rwigamba said. Former poachers are recruited to work as conservationists, and a revenue-sharing plan guarantees that 5 percent of the money earned from gorilla tourism is sent back to the communities to build schools and fund agriculture and beautification projects.
But Dr. Cranfield said poverty remains a threat to the gorillas, regardless of the behavior of local people. A lack of available health care and limited hygiene make the people and the livestock generally sicker, he said.
Because gorillas share almost 99 percent of their genes with humans, they are highly susceptible to human diseases. Human respiratory diseases are the second-highest cause of death among the mountain gorillas, trumped only by trauma from snares.
Political instability is another constant threat to the gorillas in the tumultuous region, according to the Mountain Gorilla Veterinary Project’s regional veterinary manager, Dr. Jan Ramer. Conflict in Congo makes it difficult to provide the animals with regular care and sometimes forces local people to flee their homes for the forest.
As a result, she said, gorillas can be exposed to diseases as people defecate and cough in the woods.
Dr. Ramer said even gorillas that are accustomed to humans have to be treated with extreme care. Tourists cannot eat, smoke or spit near the animals for health reasons, and doctors retreat behind makeshift blinds after darting the animals to sedate them for medical care.
Like Sigourney Weaver, who portrayed the now-deceased Dian Fossey in “Gorillas in the Mist,” doctors approach the animals by making soft gorillalike noises to indicate they come in peace, Dr. Ramer said. Ms. Fossey is credited with spearheading conservation efforts starting in the 1960s that led to the preservation of the gorilla population.
In the movie, Miss Weaver also grunted, lumbered about and munched on leaves like a gorilla to gain the animals’ trust. But Dr. Ramer said doctors no longer pretend they are gorillas.
“They know you are not a gorilla,” she said of the great apes. “We are just trying to make them feel more comfortable.”