Forest patches amid agriculture are key to orangutan survival: Study

- A recent study highlights the importance of small fragments of forest amid landscapes dominated by agriculture for the survival of orangutans in Southeast Asia.

-The research, drawing on several decades of ground and aerial surveys in Borneo, found that orangutans are adapting to the presence of oil palm plantations - if they have access to nearby patches of forest.

- The authors say agricultural plantations could serve as corridors allowing for better connectivity and gene flow within the broader orangutan population.

Over the past two decades, orangutan researcher Marc Ancrenaz watched as a tidal wave of oil palm has engulfed his once-forested research sites in northern Borneo.

When he would find an orangutan in a patch of forest surrounded by planted palms, he said he figured the animal would soon disappear.

But as the months and years rolled on, some of those orangutans stayed where they were, Ancrenaz said. Females turned up with babies clinging to their bellies, and he would occasionally spot males swaggering on the ground between the palms.

“Year after year, they were still there,” he said.

A male orangutan in Indonesian Borneo. Image by Rhett A. Butler/Mongabay.

Ancrenaz, a biologist and director of the conservation organization HUTAN, works along the Kinabatangan River in northeastern Sabah, a Malaysian state on the island of Borneo. In few places in Southeast Asia is the dominance of oil palm more apparent than in the Kinabatangan region, and it’s had a withering effect on the forests — and orangutan habitat.

“What is really surprising to us is that even in this super-degraded landscape where the forest is nearly gone, we still find orangutan in the plantations,” Ancrenaz said.

Their continued presence suggested that Bornean orangutans (Pongo pygmaeus) were adapting to this changing landscape. But it wasn’t clear whether this was a local anomaly or something more common throughout the orangutan’s range.

At first, Ancrenaz said he suspected it might be something unique about the Kinabatangan. Many people living nearby practice Islam and adhere to its taboos against eating primate meat, so they don’t hunt orangutans. Kinabatangan also has a growing ecotourism sector that relies on sightings of orangutans and other wildlife to attract paying tourists.

When Ancrenaz shared his findings with other scientists working in Borneo, however, he found that they too were seeing orangutans living in and alongside oil palm plantations.

For a study published Feb. 4 in the journal Frontiers in Forests and Global Change, the team looked at decades’ worth of data from aerial and ground orangutan surveys from around Malaysian and Indonesian Borneo. They found that some orangutans indeed have worked out a way to live in these “mosaic” landscapes that include plantations across the world’s third-largest island.

Ancrenaz said that sometimes the existence of orangutans within plantations is seen as evidence that they can cope well with these massive alterations to their habitat. “It’s not true,” he added. “Orangutans need the forest to survive.”

The research also revealed that orangutans spotted in and among plantations usually have access to at least a small fragment of standing forest nearby, which Ancrenaz and his fellow authors see as absolutely necessary to allow the orangutans to persist.

Parks and reserves are still a foundation of conservation, Ancrenaz said. But the team’s finding suggests that orangutans in these increasingly isolated islands of protected habitat may benefit from the ability to make use of agricultural plantations as well. Those bits of forest, often maintained on plantations to fulfill certification requirements from groups like the Roundtable on Sustainable Palm Oil, could be crucial corridors allowing the free flow of genetic material between parts of the larger orangutan population, Ancrenaz said.

“We need to protect the forest, and this model is still valid,” Ancrenaz said. “But it’s not sufficient.”

A young orangutan in Malaysian Borneo. Image by John C. Cannon/Mongabay.

Populations of the three orangutan species that live in Borneo and Sumatra have dwindled as forests have been cleared for timber and to make way for oil palm, rubber and acacia plantations. All three are now listed as critically endangered by the IUCN. To combat the loss of habitat, the practice of “rescuing” orangutans has increased. Conservation groups engaged in this sort of work focus on getting the animals out of harm’s way, where they might come into sometimes-violent contact with local community members or workers on the plantations. The groups then rehabilitate them, treating disease and helping them put on weight.

Ultimately, the aim of rehabilitation is often to translocate the orangutans to high-quality, protected forest where they would be in less danger.

The rescue-rehabilitation-translocation cycle is “a feel-good exercise,” Ancrenaz said, at least compared with the alternative of leaving orangutans to fend for themselves without the refuge of the tall trees where they spend most of their lives. But he also notes that the process of capturing an orangutan is fraught with risk for the animals and captors. It’s stressful for the animal and can bring them in contact with human-carried diseases that their immune systems aren’t prepared for. For the rescue team, the prospect of trying to wrangle a 100-kilogram (220-pound) male orangutan is daunting.

What’s more, a 2020 study led by Julie Sherman, one of Ancrenaz’s co-authors, found that around 90% of translocated orangutans were healthy when they were first captured. And the practice could remove individuals vital to keep the broader population stable and healthy.

Ancrenaz said the team’s findings suggest translocation shouldn’t be the “default approach.”

“We are not against translocation,” he added, “but this is a tool that should ideally be used only in the last resort when there is nothing else we can do to save the animal.”

A diagram showing the ranging pattern and ranging dynamic of wild orangutans in a fragmented landscape. Image by Ancrenaz et al., 2021.

Gail Campbell-Smith, research and conservation program development adviser with the U.K.-based NGO International Animal Rescue (IAR) in Bogor, Indonesia, said she agreed: In certain instances, orangutans should stay where they are. There are, however, situations when translocation is the only option, she said.

“We never go with the premise that translocation is a key solution in orangutan conservation,” Campbell-Smith said in an email. But, she said, each and every case must be evaluated independently to ascertain the best course to give each orangutan the best chance to survive.

“There is ‘no one size fits all’ solution here I’m afraid,” she said.

In addition to the “rescue” aspect of IAR’s work, Campbell-Smith said the organization works with land managers to protect the remaining forest and wildlife on their concessions and find “solutions to coexistence.”

It’s often a tricky situation because, in areas with less high-quality habitat and in turn less food for orangutans, resourceful apes can quickly turn to crop-raiding. While Ancrenaz notes that orangutans do little damage to mature oil palm plantations, Campbell-Smith said they could decimate young shoots, with severe financial repercussions for companies and smallholder farmers alike. Orangutans also go after community gardens, threatening an important food source for many human communities.

Proboscis monkeys along the Kinabatangan River in Borneo. Image by John C. Cannon/Mongabay.

These disturbances prime the situation for conflict with humans, in which the orangutans are sometimes killed and their babies taken for the pet trade.

To counter such problems, IAR helps farmers with strategies to minimize the damage to their crops. IAR teams also invest in developing alternative livelihoods, and the group itself employs many former loggers and hunters.

The primary goal is to avoid the circumstances that would require removing an orangutan.

“Translocation of these animals is our last ditch at saving them after every other option has been exhausted,” Campbell-Smith said.

Oftentimes, it’s because an animal is sick or hungry. Or fires set to prepare the land for agriculture may threaten an orangutan’s life or force them out of the forest and into places where they’re likely to run across humans.

IAR will translocate orangutans to a forest only after teams have carried out a suite of assessments to help predict what introducing a new animal will mean for the ecology of the area. Campbell-Smith said she sees it as a sign of success that reintroduced orangutans have been observed with babies, “bolstering the local population that was on the trajectory of local extinctions.”

“I think this is a pretty high conservation value of a project and demonstrates exactly what we do as conservation practitioners on the ground,” she said.

The study found that female orangutans living in or near oil palm plantations frequently had young — a sign that they were adapting to the altered environment. Image by John C. Cannon/Mongabay.

Ancrenaz said there are indeed situations in which translocations are necessary. Along with that, ensuring the survival of orangutans will also require larger and better-funded conservation areas. Conservationists also must engage with communities and find ways in which the presence of orangutans can benefit them, such as ecotourism.

“The big picture is to really decide if we want to coexist with this species,” Ancrenaz said.

How long they can continue to adapt to a world changing around them is still an open question.

“I cannot say that they are viable. I cannot say that they will survive there forever,” Ancrenaz said. “But if we can give them a chance, this is the best we can do.”


Article posted by John C. Cannon on 26 February 2021 on Mongabay: 
Republished with permission.


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