Lethal attraction: Plantations are deadly for infant primates 

Researchers have uncovered startling evidence that frequent visits to oil palm plantations significantly increase mortality rates among infant primates, particularly southern pig-tailed macaques. 

This finding highlights a disturbing trend where agricultural practices are directly impacting wildlife, including vulnerable young primates.

Perilous environment 

Southern pig-tailed macaques, native to Peninsular Malaysia, are increasingly drawn to oil palm plantations. 

While these areas provide easy access to food, they also expose these primates to a multitude of dangers, including predators, human encounters, and harmful agricultural chemicals. This perilous environment is proving detrimental to the survival of infant macaques.

Researchers from Universiti Sains Malaysia, the German Centre for Integrative Biodiversity Research, Leipzig University, and the Max Planck Institute for Evolutionary Anthropology conducted an extensive study over nearly a decade. 

Alarming statistics

The experts discovered that a shocking 57 percent of macaque infants died before their first birthday – a mortality rate far exceeding that in other wild primate populations. 

The team observed two groups of macaques in a landscape interspersed with rainforests and oil palm plantations. They found that prolonged exposure to plantation environments tripled the likelihood of mortality among the infant primates.

Contributing factors 

According to the researchers, this startling mortality rate could be explained by increased encounters with predators and humans, and potential exposure to harmful chemicals such as pesticides.

“Some of these risks are relatively clear: infant macaques are more likely to fall prey to feral dogs that roam in the plantations in packs or to be captured by humans and sold illegally as pets,” explained Dr. Nadine Ruppert from USM, who established and leads the field site. 

“But the potential long-term effects of the pesticides used to manage the monocultures on mammalian wildlife are much less obvious and very poorly understood.”

Accumulation of agricultural chemicals

The study further revealed an unexpected pattern of increased infant mortality linked to first-time births or long intervals between consecutive births. This contradicts previous findings that shorter interbirth intervals lead to higher mortality. 

The accumulation of agricultural chemicals in a mother’s body, which can be passed through breastmilk, is believed to play a significant role. 

“The literature suggests that certain harmful substances used in agriculture can cross the placental barrier and be passed on to the unborn offspring. We also know that certain fat-soluble molecules can be passed on through breastmilk,” said study lead author Dr. Anna Holzner.

“Accordingly, the longer the chemicals accumulate in the mother’s body, the more they could influence foetal development during pregnancy and also during lactation.”

Study implications 

The study highlights the urgent need to address the threats that agricultural landscapes pose to wildlife. The survival of infant primates, crucial for the maintenance of viable populations, is being jeopardized by our agricultural practices. 

“We know that the use of pesticides in agriculture has led to drastic declines in insect populations, so chemical analysis is essential to understand the effects of pesticides on mammalian wildlife,” said study senior author Dr. Anja Widdig. 

“Our findings underscore the critical need to implement environmentally friendly cultivation practices that minimise the risks to wildlife populations and also to people living near plantations.”

The research is published in the journal Current Biology. 

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