Monkey troopers
Experts from usm discover monkeys eat rats in oil palm estates
The solution to the long-standing pest menace at oil palm plantations in the country lies within the problem, according to a surprising find by local scientists. A study has identified the pig-tailed macaque, a known crop raider, as a natural pest control tool against rats which have been wreaking havoc at the plantations.
by LIEW JIA XIAN and LO TERN CHERN
GEORGE TOWN: Local scientists have found a “natural mechanism” to cut down the use of pesticides in oil palm plantations.
Much to their surprise, the answer is in the pig-tailed macaques – long been regarded as crop raiders themselves.
The findings followed a two-year observation by a Universiti Sains Malaysia (USM) team at an oil palm plantation in the Segari Melintang forest reserve in Perak.
“We were amazed to discover that the pig-tailed macaques, which are generally thought to eat mainly fruits and occasionally lizards and birds, also fed on rats.
“I did not expect them to hunt the relatively large rodents, or that they would even eat so much meat,” USM senior lecturer Dr Nadine Ruppert revealed in an interview.
She said data collected between January 2016 and September 2018 showed that each group of 44 monkeys killed around 3,000 rats each year.
“The crops eaten by the macaques were very little, less than 0.6% of the overall harvest,” she added.
Comparatively, she said rats were the “bad guys” for foraging an average 10% of oil palm crops.
“By allowing macaques to act as pest control, the industry could save on buying pesticides, apart from protecting the wildlife,” she said.
A report released in Current Biology, a biweekly peer-reviewed scientific journal, in October stated that the southern pig-tailed macaques were falsely perceived as crop raiders in oil palm plantations.
The report, Macaques can contribute to greener practices in oil palm plantations when used as biological pest control, concluded that the damage done by the monkeys was minimal compared to rats.
According to the report, damage from rats could amount to monetary losses of US$ 930 mil (RM3.9bil) every year.
The research was conducted by University of Leipzig PhD student Anna Holzner and led by Ruppert.
Ruppert said she started studying the primates in 2012 as part of her PhD research.
“There is not much information nor studies on the macaques, and it took us three years to get close to the monkeys,” she added.
It was only after the primates became familiar with the researchers “that we could follow them into the wild”, Ruppert said.
“We did not feed or handle them, so that they could be in their natural state.
“We want to protect these primates and their natural habitat and create forest wildlife corridors in oil palm landscapes,” she added.
On plantation workers having bad encounters with macaques, Ruppert said her team was ready to assist them in finding a solution.
“We will educate them on the best way to behave and react to the primates.
“The pig-tailed macaques live in the forest and only come into plantations that are less than 500m from the forest before going back to their habitat when they are full.
“They do not attack humans unless they feel they are in danger, or if they are regularly fed by humans or kept as pets in captivity,” she said.
Ruppert said pig-tailed macaques were a complementary species to barn owls, the widely used pest control in oil palm plantations.
“Both monkeys and owls can forage in plantations with the owls feeding at night and macaques during the day,” she added.
Malaysia is the second largest producer of palm oil after Indonesia with 90 million tonnes of lignocellulosic biomass, including empty fruit bunches, oil palm trunks and oil palm fronds, as well as palm oil mill effluent.