A new species of monkey sighted on the island of Borneo in Southeast Asia is leaving scientists worried. Apparently, it is a new hybrid fruit of the cross between a proboscis monkey (Nasalis larvatus) and a silvery langur (Trachypithecus cristatus), two different species that share the same habitat.

Far from being a cause for celebration, the occurrence of crossbreeding between distinct species in the region is an indication that the Borneo ecosystem is under pressure, and the main culprit is human action. That's because these monkeys rarely cross. According to Newsweek, this is the first time a hybrid between the two species has been recorded. It is also the second time in history that scientists observe a hybrid between two distinct species of primates in nature.

The hybrid specimen was first sighted in 2017 amid the leafy forest near the Kinabatangan River. It was a young female considered a "mysterious monkey" given the exotic look, until then not described by scientists. More recent images, taken in 2020, reveal that the animal grew and gained a cub. The researchers noted that the monkey was living in an area where proboscis monkeys and silver langures shared space.

The two types of monkeys are distant relatives, but differ markedly in both traits and size. Proboscis monkeys have large pink noses and faces and grow up to 76 cm, weighing on average 20 to 24 kg. Less well known, the silver langur has a much smaller nose and a black face, reaching up to 56 cm and 6.6 kg.

Both species live in "families" with one male and several females. With territory increasingly vulnerable and pressured by the advance of humans, monkeys are possibly competing for smaller space and companions to form new families.

According to the researchers who analyzed borneo's "mysterious monkey," with less and less territory to branch out, the proboscis monkeys appear to be mating with the silver langur females. The hybrid monkey has physical characteristics of both species – as described in a study published in the scientific journal International Journal of Primatology.

"Seeing this supposed hybrid is an alarming symptom of an ecosystem that seems unbalanced," said study co-author Nadine Ruppert, a primatologist at the University of Sciences malaysia. The scientist was also impressed to see that the hybrid female was with a baby monkey. This is because most hybrids born of different species are sterile and unable to produce offspring.

"She seemed to be nursing a baby," Ruppert told Live Science. "We were all amazed. It was quite surreal." Although it is possible that she was taking care of another female's baby, the scientist points out that she appeared to have swollen breasts, suggesting she was in the process of breastfeeding.

Despite the rarity of the circumstances, the researcher reinforces the alarming character of this finding. "It is tragic that both species now accumulate in the remaining narrow areas of riparian forest surrounded by oil-on plantations, where they compete for food and mating opportunities," he said. "I hope people start talking about it, not as an attraction, but as a 'flagship' animal of the area that needs to be protected, and with it, its two mother species and their habitat."

Source: Um só Planeta