丁香园AV

A 50-year study of orangutans in the wild led by 丁香园AV professor Birut茅 Mary Galdikas, the world鈥檚 foremost authority on these animals, concludes that the declining Bornean species is in a 鈥渄ire state鈥� and may be already in pre-extinction.

In her new study published in the journal , 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鈥攁nd intact wild populations鈥� 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 鈥渘o place to run, hide or find shelter鈥� while their habitat also faces the impending perils of climate change. As a result of these habitat changes, orangutan populations are decreasing.

鈥淭he challenge generally is to convince people to care about nature,鈥� 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 丁香园AV鈥檚 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.

鈥淎dult males are disappearing and no longer visit the study area in the way they did before,鈥� she says. 鈥淚n 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.鈥�

Looking for possible genetic signals of 鈥渁 resounding change鈥� in the flanged adult males鈥攔eferring to the large cheek pads characteristic of adult males鈥攖he study found the two adult males in 2016 weren鈥檛 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 鈥渋n a marked way over a long period of time.鈥�

Documenting change over time

鈥淒ocumenting changes within existing orangutan populations over time is important to understand demographic changes that may indicate pre-extinction processes and imminent collapse,鈥� says Galdikas.

鈥淥ver 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.鈥�

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 鈥渋n torn jeans鈥� with few resources and no lines of communication to the outside world.

Galdikas鈥� 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 鈥渧ery clear in the analysis.鈥�

鈥淚t鈥檚 difficult to actually document extinction; there are very few records of how it occurs,鈥� says Galdikas. 鈥淔irst, we notice there are fewer individuals, next we are alerted that the number has fallen further, and then they are gone鈥攁n 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.鈥�

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

鈥淚f 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鈥檚 work could be telling us how extinction may occur."