Five-decade study of wild orangutans points to new urgency as “pre-extinction” looms

A 50-year study of orangutans in the wild led by Simon Fraser University professor Biruté Mary Galdikas, the world’s foremost authority on these animals, concludes that the declining Bornean species is in a “dire state” and may be already in pre-extinction.

In her new study published in the journal Biodiversitas, Galdikas details five decades of observational study in the forests of Borneo that has succinctly captured orangutan movement and lineage. She concludes that more conservation efforts are needed to keep as many individual orangutans—and intact wild populations— alive as possible.

Galdikas says creating a few 100-kilometers-long corridors would allow males to travel. Adult males can no longer roam as they once did in the past due to increasing habitat disruption. After they become adolescents or sub-adults, males typically leave their families and become nomadic, until as dominant adults they settle down to mate for an indeterminant period of time.

Massive deforestation carried out by palm oil companies, timber estates and development are leaving orangutans with “no place to run, hide or find shelter” while their habitat also faces the impending perils of climate change. As a result of these habitat changes, orangutan populations are decreasing.

“The challenge generally is to convince people to care about nature,” says Galdikas, who at 77, continues to follow orangutans in the wild, adding timely new observations to an already exhaustive cache of field data. She also continues to inspire students by teaching in SFU’s Department of Archaeology.

Her latest study details her half-century of tracking orangutans who roam in the study area she established in 1971, known as Camp Leakey in Tanjung Puting National Park, located in Central Kalimantan, Indonesian Borneo.

The study outlines a possible case for pre-extinction by detailing findings of genetic data collected in 2016, which provides some explanation of the changes occurring in the wild population over 50 years.

“Adult males are disappearing and no longer visit the study area in the way they did before,” she says. “In particular there were only two wild flanged adult males found in the region in 2016. Three decades ago, there were as many as 24 wild adult males.”

Looking for possible genetic signals of “a resounding change” in the flanged adult males—referring to the large cheek pads characteristic of adult males—the study found the two adult males in 2016 weren’t related to each other, but were each related to different females.

Overall Galdikas found the number of typically long-lived, adult males in the study area decreased “in a marked way over a long period of time.”

Documenting change over time

“Documenting changes within existing orangutan populations over time is important to understand demographic changes that may indicate pre-extinction processes and imminent collapse,” says Galdikas.

“Over time something has happened. We can see that clearly. Anyone who visited the study area for a brief time would see that there were numbers of females, juveniles, infants, and a few males, so things might seem normal. But observations over time tell a very different story about the males.”

Since first starting in 1971, tracking orangutans has typically meant up to 20 days of constant dawn-to-dusk walking within the study area. Galdikas recalls starting out roaming the forest “in torn jeans” with few resources and no lines of communication to the outside world.

Galdikas’ former husband, Rod Brindamour, and local assistants created a trail system spanning 125 kilometers to help search for and locate wild Bornean orangutans, who spent 99 per cent of their time in the trees, and to collect behavioral data, a process made somewhat easier by the fact that orangutans are typically slow travelers.

Wild observational data were collected every year from 1971 to 2023. For analysis, data were extracted from 1976, 1986, 1996, 2006 and 2016 to check the number of adult and sub-adult males in the study population during those years.

Demographic changes may be key

The decline of adult males over those years became “very clear in the analysis.”

“It’s difficult to actually document extinction; there are very few records of how it occurs,” says Galdikas. “First, we notice there are fewer individuals, next we are alerted that the number has fallen further, and then they are gone—an example is the Javan tiger of the 1980s. Scientists assumed tigers were still there, did a study in the 1990s, and found nothing, no tracks, no carcasses, nothing. They can go, right in front of us, as we are watching.”

Documentation needs to be continuous she insists. “If we look at the characteristics of extinction, maybe extinction is being foretold by demographic changes, such as adult males becoming fewer; it’s a sign. Each species has its own characteristics and ecological context, but demographic changes may be key in foretelling extinction.

“If this is happening to one of the largest orangutan populations in the world, then something is happening to the species in the wild. I would hope to be wrong but my life’s work could be telling us how extinction may occur."