The Dietary Impacts of Deforestation on Macaca fascicularis (Long-Tailed Macaque) using Metabarcoding

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Primate poop exposes how animals adapt to deforestation. Searching through monkey faeces has revealed exactly what they eat, and how this changes as their environment is destroyed. Across the world, many primate habitats are under threat from deforestation. Can primates adapt their lifestyles to these changing environments, and if so, how? In a search for answers, researchers at Imperial College London extracted DNA from stool samples of the Long-Tailed Macaque from the lush Bornean rainforest, and also a man-made plantation where pristine forest once stood. But why poo? Every living organism contains a unique DNA code, and the DNA stored in whatever a monkey eats will pass through its digestive system and end up packaged in the poo. Thus, by ordering through all the DNA in the poo you know exactly what the monkey has been eating since its last bowel movement. Previously, processing all this DNA was labour intensive and expensive, however an exciting new technology known as Next Generation Sequencing (or NGS) makes this possible with a single experiment. Diet is arguably the most important life factor that determines how an animal lives. Frugivores eat fruit, folivores like leaves and insectivores eat insects – different primate species consume varying ratios of these three resources. The balance of these foods in various ecosystems will determine which species are best suited each environment. In Borneo, deforestation targets fruit trees (dipterocarps) which spells trouble for those frugivores who would otherwise flourish in lush jungle. If this forest is altered, and the balance disrupted, will they be able to supplement their diet with other foods in order to survive? Adaptable Omnivores Luckily for the Long-Tailed Macaque, despite preferring fruit, they are omnivorous which means they can eat a combination of plants and animals. They are known to be hardy and adaptable, often seen living alongside humans in semi-rural environments. Their dietary flexibility makes them a suitable subject for researchers when exploring diet in a very disturbed ecosystem. Analysis revealed that Macaques in a plantation are surviving on a completely different diet compared to those in natural rainforest such as tarsiers who specialise on insects, or langurs who primarily eat leaves. These species could get outcompeted as the environment changes, possibly driving them towards extinction. The results have given scientists an idea of how long tailed macaque diet changed. Macaques in the disturbed forest ate proportionally more insect species such as many types of ant and shield bugs. They also ate plants common to deforested areas such as grasses, climbing wild pea, and even some domestic melons from the nearby forest workers! The macaques in the pristine forest were eating much more fruit – in particular figs. With little to no overlap in diet between environments, the study demonstrated that Macaques were able to adapt their diet to a dramatically different habitat by supplementing their otherwise fruit heavy meals. This omnivorous advantage in threatened forests is important as it widens their diet to more readily available resources and could be the difference between life or death. Faecal samples from the plantation also contained some bird DNA. It is highly likely that some Macaques opportunistically ate birds’ eggs, this may be damaging for threatened bird species with no way to defend from the primate intruders. This is only one direct observation; more analysis will reveal what else could be in danger as species’ habitats are forced to overlap. Ecosystems are carefully balanced, and even a small unnatural change can cause large changes in ecosystem composition. This study has exposed a conundrum; a flexible diet will likely aid species when confronted with destruction of their natural habitat, but will the hardiness of the survivors cause those less adaptable to suffer as they become gradually outcompeted? The next step would investigate a species with restricted diet, such as the Red Leaf Monkey or Orangutan, and perhaps research a way to discover not only what, but exactly how much of each food these animals are eating. One thing is certain, diet is an essential life factor which will directly influence the long and short-term behaviour of species, potentially causing a cascade of species extinction if the ecosystem balance gets tipped over the edge. Applying new technologies to this field is a big step towards understand the ever changing dynamics of threatened ecosystems.

Primates are increasingly threatened due to habitat destruction. Agricultural plantations in Borneo, Malaysia, comprise 15 percent of land use, and logging of pristine rainforest is removing natural primate habitat. Understanding how primates adapt to secondary habitats is a fundamental step towards implementing successful conservation programs. I explored the diet of Macaca fascicularis (long-tailed macaque), a generalist primate species, to understand the repercussions of dietary flexibility. Plant, arthropod, and vertebrate DNA was extracted from Macaca fascicularis faecal samples in pristine Bornean rainforest, and an Albizia timber plantation. Illumina sequencing produced a full dietary breakdown for each sample. The proportion of plants and arthropods was not significantly different between environments, however the taxonomic composition of each group greatly varied. The pristine forest macaques were found to have a diet based mainly on flowering plants, and Lepidoptera larvae. The plantation macaques had a more balanced diet and would travel to find Ficus, as well as eating introduced plants and ants. M. fascicularis ate food that was harder to acquire in the plantation, but may have had nutritional benefits that out-weighed the costs. I propose that M. fascicularis consumes taxa in line with the ‘optimal foraging theory’, expending as little energy for the best gain. I also explore how M. fascicularis changes its diet in proximity to humans, and question the potential impacts their adaptable nature could have on ecosystem balance.