African Swine Fever has devastated wild pig populations in Sabah. To understand its impact on the animals, the forest, and people, data is needed. But counting pigs is tricky. This is Part 1 of a two-parter on the impact of the disease.
IT IS December 2020 and in the Lower Kinabatangan Wildlife Sanctuary, Sabah, a dead Bornean bearded pig (Sus barbatus) lies on the ground. It was the first of 14 that would be found in the following weeks.
“We knew something was very wrong when more pig carcasses started to pop up,” says Dr Benoit Goossens, director of the Danau Girang Field Center, which is located there.
(Photo: Since ASF, camera trap photos of wild pigs like this one from 2013 are rare | Pic by Danau Girang Field Centre)
That discovery was the first report of African Swine Fever (ASF) in Sabah. ASF is a highly contagious viral disease affecting pigs and can kill them in as few as 6 days.
From media reports and interviews with scientists and locals, the disease is decimating wild pig populations in Sabah. Currently, the outbreak is on-going as there is no treatment for ASF.
To control its spread, the state instituted culling, suspended hunting of wild pigs and cautioned against wild pig consumption.
If so many wild pigs have died from the outbreak, how is this affecting the forest ecosystems? This worries one tropical forest ecologist.
Sui Peng Heon was reading the newspaper when she learned about the ASF outbreak in the Kinabatangan area in March last year. She is a research team lead with the Stability of Altered Forest Ecosystems (SAFE) Project, Sabah.
Her team has been monitoring populations of medium sized mammals such as the bearded pig in the Kalabakan Forest Reserve since 2010.
“There are severe gaps in our understanding of bearded pigs,” says Sui. Calling them the “gardeners of the forest”, she says wild pigs contribute to essential ecological services in maintaining forest biodiversity in Malaysia.
However, no thanks to the lack of scientific interest and dedicated funding for wild pigs, even the basic biology of wild pigs is “very poorly understood”.
Goossens agrees. “There are not many studies on what they do, how they contribute to the forest and what would happen if they were not there.”
With ASF impacting these ‘gardeners’, what is happening to the forest? Sui and her team are determined to find out.
Barriers to counting
But getting information about the outbreak has been difficult. To begin with, nobody has counted wild pigs in Sabah, though there are estimates of where they live, says Sui.
Scientists could not run field surveys due to strict movement control orders (MCOs) implemented to curb the concurrent Covid-19 pandemic raging through Sabah.
So scientists turned to crowd-sourcing for information on the ASF impact. “Have you seen any dead pigs? How are the pigs doing in your area?” they asked on social media. They shared findings with colleagues and the government.
That quickly formalised into the Babi Hutan Project Borneo, a citizen science project to track bearded pigs.
A collaborative project of Imperial College London, the Sabah Wildlife Department, and Sabah Department of Veterinary Services (DVS), the project invites the public to report details and submit photos of ASF-infected pigs.
Despite their efforts, the project’s data could not conclude on the severity of ASF, says Sui. The data comprised primarily anecdotal evidence and had huge discrepancies in everything from timelines to numbers of dead pigs.
Macaranga has been contacting the DVS for data and comments since November last year but has had no response to questions. Macaranga is therefore referring to validated data by the Malaysian DVS available on the public platform, World Organisation for Animal Health (OIE).
OIE sent Macaranga data from the date of the first confirmed outbreak on 8 February 2021 to 22 October 2021 (see below).
Interestingly, the data does not reflect the scale of devastation of ASF as reported by the media, locals and researchers. There were 38 ASF outbreaks in that period but the total verified number of deaths was 1,454. This comprised 72 wild pigs and 1,382 commercial pigs (including culled animals).
On the contrary, mass culling was announced by the state in February 2021 when the first ASF cases were detected among farmed pigs in Pitas district. The Star reported that 2,000 commercial pigs and 1,000 wild bearded pigs would be culled to counter the outbreak in the Pitas district alone.
However, according to the OIE data, in Pitas, 315 commercial pigs succumbed to ASF and only 25 were culled. No infected wild pigs were recorded.
For commercial pigs, the data appears to suggest that not many farms have been affected. According to federal DVS estimates, there were 89,627 commercial pigs in Sabah in 2020. The OIE data indicates that only a small number of that has been verified as affected.
Nonetheless, as of January 2022, the Star reported that 20 of Sabah’s 23 districts had been declared outbreak districts, 10 of which were by then ASF-free.
Macaranga could not verify commercial pig data and reports with the DVS, pig farm associations or commercial pig farmers, except for one commercial pig farmer (see below).
As for wild pigs, scientists aver that pig numbers have plunged. Goossens says his research centre’s camera traps in Kinabatangan show this.
Before ASF, large families of wild pigs were regularly observed on camera traps and sighted along the Kinabatangan River. Tracks were observed in the forest.
But these sightings have plummeted since the outbreak. Goossens reckons that Kinabatangan has lost 90% of its pigs based on the impact of ASF as published in scientific findings elsewhere.
“Usually what happens with ASF, about 90—95% of the wild pig populations are killed.”
The Covid factor
Collating data on wild pig deaths is extremely challenging, says Sui. The MCO meant rangers, researchers and even recreational hikers could not enter pigs’ forest habitats in protected areas.
By nature, bearded pigs are already difficult to spot, with the males especially being solitary creatures unless it is breeding season, she says.
“They are widely distributed across a large spatial area, so it is unlikely you would notice many dead pigs or be alarmed [by them].”
Equally challenging is getting data from other wild pig habitats like oil palm estates and state forests near villages. Sui suggests that workers and villages did not understand the significance of dead pigs and did not trust authorities enough to report them.
Impact on forests
Sui hopes to bring the project to its next stage of investigating the ecological impacts of such a large drop in wild pig populations and recovery of the populations
“The bearded pigs are the most likely creatures you will encounter when you enter a forest. They’re a very good indication generally of how the ecosystem is doing because they are resilient.”
Bearded pigs are also important for forest regeneration.
When pigs consume seedlings and turn over the soil, they contribute to top-down control of how many seedlings tend to survive and become saplings.
Competition and diversity
Without them, Sui says “there could be uncontrollable sprouting of most seedlings into saplings and stiff competition in the understory. They [the seedlings] have to compete for more resources to grow into trees, which affects forest dynamics quite a bit.”
What’s more, wild boars shape tree diversity. Female pigs construct birthing nests using hundreds of tree saplings from different areas.
A 2021 scientific paper by Matthew Luskin and his colleagues suggests that the lack of wild pigs in “defaunated forests may be missing these wildlife disturbances that contribute to the maintenance of hyperdiverse (very diverse) plant communities”.
Despite the gloomy backdrop of bloated pig carcasses across Sabah, both Sui and Goossens are optimistic that the wild pig populations will bounce back.
Says Goossens, “Pigs are really resilient. (ASF) hasn’t wiped out the whole population; we still have evidence of pigs in our area. There have been photos taken of pigs and their piglets. They are a fast-reproducing species.”
“It might take 2 to 3 years but I am pretty sure they will recover.”
A note on terminology: we use ‘commercial pigs’ to refer to pigs that are farmed, whether in large farms or backyards; we use ‘wild pigs’ interchangeably with Bornean bearded pigs (Sus barbatus). Update 18 February 2022: the information about the wild pigs being solitary creatures has been corrected to “male pigs being solitary creatures”.
[Edited by YH Law]
In Part 2: Has the decimation of wild bearded pigs hurt the Kadazandusun community, whose economy and culture are tied to hunting, consuming and selling these animals?
This story was produced with the financial support of the European Union in the form of a grant from Internews Malaysia. Its contents are the sole responsibility of Internews and Macaranga and do not necessarily reflect the views of the European Union. Kymberley Chu also received training under the Macaranga Sprouts programme.
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