The far-ranging impacts of Borneo’s vast palm oil industry are well known, from the extinction of the orangutan to the destruction of the once pristine rainforest. Yet far less is understood about how these vast plantations are affecting other ecological processes that also play a significant role in the forests.
This paucity of knowledge has spurred researchers to look at what is happening to the populations of scavengers over a scale of environments reflecting human disturbance, ranging from untouched rainforest to heavily managed palm oil plantations, publishing their results in PLOS One.
While little attention is given to the role of scavengers, their importance to the ecosystem cannot be overstated. The animals play an integral role in scouring the rainforest for the carcasses of animals to feast upon, contributing to the recycling of nutrients and helping to prevent the spread of disease. Interfering with these processes could result in some incredibly serious implications not only for the wildlife, but the people who live close by.
Focusing on these oft-maligned creatures, researchers assessed which scavengers were using which habitats, starting with virgin rainforest, and moving to various stages of logged forests, before ending on full palm oil plantations. They found that while the two most common animals they managed to catch were the Malay civet and the fulsome Southeast Asian water monitor lizard, they also recorded mongooses, otters, pigs, and bears.
But what was of particular interest was how these communities of scavengers shifted as they moved into the most human-dominated and disturbed forests. The virgin forests were dominated by the mammals, with only a few smaller monitor lizards recorded. But as the researchers moved into the more heavily disturbed environments, they found that the number and size of lizards rocketed. In the plantations, it appeared the lizards were wearing the trousers, so to speak. In fact, among the palm oil trees, the only other scavengers they found were civets.
The success of the monitor lizards seems to be occurring at the expense of their mammal competitors. As the plantations typically only contain a single species of tree there are few other species surviving and thus little prey. The monitor lizards, however, will eat pretty much anything, and so can take advantage of the trash and refuse left behind by the humans working in these plantations.
This means that they have come to dominate in the wastelands of the plantations. This abundance of trash also seems to be making the lizards bigger, and even attracting in males from the surrounding forests, skewing the sex ratio of the population massively towards the fellas.
How this will affect the ecosystem in the long term is not known, but it is not expected to be good.