The challenge of macaque management


THERE was fuss when it was revealed that 97,119 long-tailed macaques had been culled in Peninsular Malaysia in 2012, while the federal wildlife authority noted in a later report for 2013 that a further 68,413 macaques were culled that year.

Some Malaysians were shocked, and condemned the practice. But unless we are to believe that the wildlife authorities have nothing better to do, and kill monkeys for fun, then surely there must be a reason.

Since then, the issue of culling of wild monkeys has largely – although not entirely – gone quiet. Apparently, the issue is just one of many “sensitive subjects” that we are enjoined to not raise.

The white variety of the red langur in Tawau Hills is injured by an attacking long-tailed macaque, as witnessed by observers.The white variety of the red langur in Tawau Hills is injured by an attacking long-tailed macaque, as witnessed by observers.

As a professional biologist and resident of Malaysia since the 1970s, with experience and knowledge of the harm caused by macaque monkeys to human welfare and business, as well as to other wildlife species both directly and indirectly, I feel that it is overdue to acknowledge and understand this elephant-in-the-room topic.

The issues really need to be resolved.

Two species of macaque monkeys are involved: the long-tailed macaque, known as kera, and pig-tailed macaque, known as berok or, in Sabah, gebuk. Both species occur in all three regions of Malaysia.

On a personal level, this story goes back to 1975, when I received a scholarship from the British government to study berok in Pahang. After three months, I could find none in my allocated study site in the dipterocarp forest of Krau Wildlife Reserve.

Later, I realised that troops of this monkey species typically roam over areas in excess of 3sq km. In natural forests, they are “here today, gone tomorrow”.

This is very different from other primate species, where one troop of leaf monkeys or gibbons, for example, will typically spend most of its time within less than half a square kilometre, and one can usually find the same troop again within a day’s searching.

When one of my daughters left Kota Kinabalu in 2000 to begin her study in Universiti Malaya, I asked her how she is, and was informed that one of her biggest concerns were macaques almost daily entering bathrooms and kitchens.

Most universities in Malaysia have unresolved problems with macaques. In November 2023, for example, a dead macaque was found inside a water tank in Universiti Malaysia Sabah. One thirsty macaque made life unpleasant for hundreds of students for several weeks thereafter.

Unlike most wildlife species, the macaques have adapted supremely well to the expansion of human interests into what was formerly natural forest land.

The 13 field staff of my non-governmental organisation, Borneo Rhino Alliance (BORA), live in the same patch of forest-oil palm estate edge that is shared by more than 200 pig-tailed macaques. Along the road to Lahad Datu, there are a few hundreds more pig-tailed macaques.

Some 10km further down the road, there are several large troops of long-tailed macaques. Two large, old wild fig trees there have died as a result of macaques constantly nibbling at leaf shoots.

We have experienced frequent and costly damage by macaques to our electricity supply, roofs, vegetables and nursery. Their food, apart from theft of human food and miscellaneous items including grass shoots and seeds and insects, consists in large part of oil palm fruits.

One of BORA’s roles is to grow orangutan food plants in oil palm plantations. In our experience, of almost 9,000 such food plants that we have planted in 20 sites, the single biggest cause of damage to and death of those plants is macaque monkeys. They turn out to be a more serious threat to the survival of young plants than drought, floods, insects and elephants.

The forests of the Kinabatangan Wildlife Sanctuary, and most forest patches in the Kinabatangan district of Sabah, are now filled with macaque monkeys of both species.

This is very different from four decades ago, when one would see sparse groups of long-tailed macaques only along the river banks, and no pig-tailed macaques at all.

For myself, having been a visitor to that area since 1983, my impression is that a contributory factor in the decline of the wild orangutan population there is the stress imposed by macaques.

The stress would result both from a reduction in food availability (the macaques being the most aggressive feeders on fruits) and the physiological and emotional stress of dozens of monkeys constantly harassing single orangutan.

The current situation of gross over-population of macaques in protected areas is serious yet largely unknown. In one state park in Sabah, for example, they devour entire cohorts of Wallace’s flying frog eggs, and attack and sometimes kill red leaf monkeys.

Arguably, the most worrying issue with Malaysia’s massive and ubiquitous macaque population is that the majority of wild macaques of both species, at least in Sabah, carry the so-called monkey malaria, Plasmodium knowlesi, which is the commonest form of malaria occurring by humans in Sabah.

I hasten to note here that the objective is not to demonise macaques but, firstly, to stop this issue being too sensitive to discuss and, secondly, to work towards a management solution.

We must be careful to understand the difference between individual animal welfare, and the need to manage the entire population – in this case of macaques. I also wish to note that the IUCN classification of long-tailed and pig-tailed macaques as endangered is not only misleading but undermines the credibility of the IUCN and the need to manage wild macaque populations.

Put simply, the need is to sustainably reduce the Malaysian macaque populations to levels that are in tune with the health of wild plants and other wildlife species, and with human welfare.

Instead, the aim is to reduce the population to a level that significantly reduces conflict with human interests, and to sustain that level in the long term. Every time we see a group of wild macaques, it is clear that the demography is excellent for continuous population increase.

Numbers are limited only by food availability. Mortality from human agency or from other wildlife species is extremely low.

During the 2013 debacle, the Peninsular Malaysia wildlife authority stated that an “inventory” of the macaque population in 2007 showed there were 740,000 macaques across the peninsula. My own guess is that this is a significant underestimate.

Such is the fertility of macaques, an “offtake” of say, 100,000 individuals per year out of 740,000 is a drop in the proverbial ocean. If you take out 100,000, there will still be in excess of 250,000 fertile females, and that will just allow space and food for a next generation of 100,000 macaques to be born and live. Overall numbers will be back up to the maximum within five years.

There seem to be only four ways to tackle the problem of too many macaques. The first is to do nothing, and pretend that there is no problem. This is what we see now.

The second, apparently recommended by some mainstream voices, is to translocate “problem macaques” from wherever they are now, to other places.

We must realise and acknowledge that this is the worst of the four possible options. In any operation to capture macaques alive, given that they live in groups of many tens of individuals, and there are usually other groups not far away, then only a proportion of the total number of macaques present can be captured.

If you remove that captured proportion, the remaining macaques will simply breed and bring numbers back up to the local maximum carrying capacity. The problem will not be solved at that problem site.

But worse still, wherever the captured macaques are moved to, one of two outcomes will occur. One possibility is that these animals will cause mayhem in the new site, whether or not there are existing macaque troops present. The other is that they will lead a miserable existence with poor nutrition, because there is insufficient food productivity.

The third option is a programme of sustained and large-scale culling. There are both ethical and practical problems with this approach.

The practical one is that, as shown by Perhilitan’s past experience, even annual removal of, say, 100,000 macaques makes hardly a dent in human-macaque conflict situations.

A more pragmatic approach might be to target total culls of certain small, isolated troops, such as occur on university campuses. Of course, the methods must be chosen to avoid pain and suffering. But this does not fit with the ethical concerns of some commentators, who are against any killing of any animal for any reason.

The fourth option is to introduce and sustain a programme of contraception, specifically vasectomy for males, wherever there are problems between humans and macaques. If done again and again, consistently, the birth rate will be suppressed significantly, and population size will decline wherever the programme is conducted.

In conclusion, the case of macaques points to a more general issue concerning Malaysian wildlife. There is “no one size fits all” in wildlife management.

Some wild species are now in very low numbers, scattered in distribution, with low birth rates and perhaps insufficient food supplies to allow recovery. Interventions are needed to boost births and population size. This would apply to the Malayan tiger and the seladang.

For macaques, numbers definitely do need to be moderated, by implementation of agreed regional programmes. There is no fear of extinction, despite the IUCN classifications.

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