With monkeys, specifically toque macaques, becoming the target of discussion once again amidst plans of exporting them to China, preventing crop damage has become a growing imperative with the frequency of monkeys raiding crops.
Agriculture Minister Mahinda Amaraweera has claimed that as per a Hector Kobbekaduwa Agrarian Research and Training Institute (HARTI) report submitted to the ministry, the toque macaque has been identified as the animal that causes most crop damage, having destroyed 200 million coconuts last year.
In the article ‘Problems with Pest Monkeys: Myths and Solutions’ published in LORIS in 2012 by Smithsonian Primate Biology Programme Director Dr. Wolfgang Dittus, who has undertaken extensive studies on toque macaques in Sri Lanka, several causes for increased human-monkey conflict are outlined.
These include the fact that only a limited number of monkeys can live in any one area proportional to the amount and quality of available food and water, the inability of national parks to support greater numbers of monkeys, and the clearing of forests depriving monkeys of their home and supply of natural foods. The last cause also entails the transformation of monkeys into pests once natural forests are replaced by rice fields, vegetable plantations, etc., which provide water and food sources that support primate survival.
The article underscores findings to the effect that “monkeys that have access to human foods have increased exponentially in number,” with “some towns and villages, by way of their excess of food litter, having turned into public monkey breeding farms”.
Speaking to The Sunday Morning, University of Peradeniya Faculty of Agriculture Professor Buddhi Marambe said: “When the population starts expanding and the natural habitats do not provide adequate food for them to live, naturally, wild animals will start encroaching on human habitats. Clearing of forests and encroaching on their land have contributed to limiting the area available for the wild animals to live.”
Prof. Marambe noted that while only estimated values on damage caused to crops by monkeys were available at present, crop damage by wild animals, including monkeys, had seen a significant rise.
“We have been discussing this for a long period of time. Everyone, including politicians, have recognised the issue, but the effective implementation of the remedies is the problem right now.
“The meeting we had in December last year at HARTI provided a window for all concerned parties – animal lovers, affected agriculturalists, and administrators – to collectively agree that something has to be done. At that meeting, though we did not come up with a methodology, there was an agreement that there should be a control of this particular menace as soon as possible before agriculture and food security of the country was further damaged.
“This is a positive outcome, since everybody, even animal lovers, do understand that there should be some control measures. But the most effective control measure to be applied is still an issue.”
Farmers’ concerns
Meanwhile, speaking to The Sunday Morning, All Ceylon Farmers’ Federation Convener Namal Karunaratne noted that the damage caused by monkeys to crops was a problem that had persisted for a while, with their destruction taking on numerous forms.
“In addition to eating and plucking the coconuts, monkeys also destroy the buds while jumping across coconut trees,” he said. However, as mitigation strategies, farmers lacked solid or longstanding solutions, he noted.
“Farmers have no effective measures against monkeys. They sometimes use catapults and air guns, the latter which is not accessible for everyone and impractical because bullets are expensive. They now also wear masks that look similar to the monkeys and yell to frighten the animals when troops arrive. Sometimes they resort to throwing stones or hooting, but monkeys eventually get used to these disturbances.
“As such, these measures are not fully successful and are only effective 25% of the time, since even if monkeys are chased away, they will return later. For instance, the monkeys that are chased away from one plantation will simply move towards a different plantation and cause damage. These measures are therefore only a temporary form of relief for farmers.”
Accordingly, he stressed that a long-term and scientific solution was urgently required, adding that forests must be made hospitable to wild animals so that they could sustain their food requirements.
Remedies against monkeys
Attempts to deal with monkeys have included culling, chasing, translocation, sterilisation, and preventing monkeys’ access to food, with varying degrees of success. Dr. Dittus notes several downsides to some of these methods, pointing out that killing is not effective in the long-term while translocation is ineffective and harmful to people and monkeys. Meanwhile, sterilisation is costly, impractical to carry out on a large scale, and does not immediately rid a community of pest monkeys.
He therefore proposes preventing monkey access to food as the best option, especially for toque macaques, since it stops monkeys visiting areas where food or water are absent while a reduction in their food and water supply eventually reduces their population numbers.
Prof. Marambe noted that scientifically-defined selective culling would be one of the effective techniques to resolve the issue of pest monkeys.
“Scientifically defined selective culling of wild animals is one of the ways most countries have adopted. But in Sri Lanka, when religion comes before regulation, it’s a very difficult practice or directive to implement.”
He emphasised that selective culling was not the eradication of the species. “That’s not the way to tackle the problem. Selective culling is the management of the species by reducing or minimising the population to a manageable level, especially in terms of crop damages that they have caused.
“I do not know whether it’s prudent or easy to move people out of the areas that they have been cultivating in at present. Several measures have been implemented, like the electric fence, etc., with respect to the wild elephant. Wild animals that follow the terrestrial rules are easily detected, but wild animals that have an aerial route, such as peacocks, giant squirrels, and monkeys, are the most difficult ones to control.”
In the meantime, long-term remedies such as sterilisation were also being implemented, he noted.
“Immediate solutions will have to be given to the farming community, especially to save their crops, since Sri Lanka is in a dire situation at present,” he said, adding that efforts were underway to ensure that the contribution of the country’s agriculture sector could be maximised in achieving food security. “Such efforts will be in vain if such macro pest problems are not solved in the immediate future as well as in the long-term.”
No one-size-fits-all solution
University of Colombo Department of Zoology and Environment Sciences Professor in Zoology Sampath S. Seneviratne too noted difficulties with controlling monkey behaviour.
“The problem with the toque macaque is that it is intelligent, so whatever the farmer tries to do, they try to counter. The toque macaque is particularly aggressive because it eats everything that humans eat. It is very crafty and works around whatever the mitigation measures we devise,” he said.
Accordingly, he noted that there was no one-size-fits-all solution to offset the losses caused by monkeys to crops. However, he outlined a few solutions.
“In certain areas, one option for some seasonal crops is to shift to crops that are less susceptible to monkeys. For instance, monkeys are not attracted to sugarcane, but they go for corn. Of course, farmers don’t have this option with multi-year crops, which shows that solutions are not one-size-fits-all.
“For farmers who grow seasonal crops that are closer to the ground, keeping the monkeys away is relatively easy, since there are options such as having a dog, electric fences, or removing trees around the perimeter so that monkeys can’t use the trees to access the plantation.
“Farmers growing multi-year crops such as coconut, pepper, etc., where it takes a while for the crop to grow and yield a harvest, need more innovative strategies. Coconut farmers can clear the perimeter of their fields so that it prevents monkeys. Another solution is to have a watcher for the crop.”
In related research, Dr. Dittus too has recommended this option of dawn to dusk watchers for defending crops against raiding monkeys, noting that “once monkeys have learned that no food can be gained from raiding, they seek their diet elsewhere”.
“Crops can be shielded from monkeys by buffer zones. In Sri Lanka, the forest-dwelling toque macaques shun crossing open ground: this reluctance can serve in the defence of crops. To be effective, however, the buffer should be at least 100-200 m wide, devoid of trees, shrubs and food sources; pasture could serve this purpose. The buffer should be ‘no man’s land’ for monkeys and crop farmers,” his research notes.
Stressing that the solutions to preventing crop damage from monkeys varied according to crop type as well as location, Prof. Seneviratne also pointed out that monkey behaviours should also be considered in preventing crop damage.
“In most cases, monkeys are nomadic, meaning a troop would patrol a large area and settle in areas with less disturbance. Accordingly, if monkeys are chased away frequently, the likelihood of them targeting the plantation becomes less.”
Prof. Seneviratne pointed to the rapid deforestation and erosion of natural resources as another significant issue, noting that ensuring that the wild animals had access to more forest lands would be one of the main solutions to the crop raids.
Meanwhile, Minister of Agriculture Mahinda Amaraweera said that with the plans to export monkeys being halted, a new solution to crop raiding monkeys would be required.
“Since we don’t have the solution of exporting monkeys, we are waiting for a new solution to be provided. Environmentalists, etc. have to provide this solution,” he said.