Several endangered species of monkey are likely to be pushed further towards extinction by the effects of climate change, research has suggested.

At least four primates from South America that appear on the international Red List of endangered species are adversely affected by climate phenomena that are predicted to worsen as the world warms, scientists have found.

The muriqui, the Colombian red howler monkey, the woolly monkey and Geoffroy’s spider monkey, have all declined in population either during or soon after recent El Niño events, according to a study from a team at Pennsylvania State University.

Many scientists expect El Niño events, in which abnormally warm ocean temperatures in the southern hemisphere affect the climate, to become stronger or more frequent over the next century.

This could create fresh pressures on species that are already under threat. The muriqi and Geoffroy’s spider monkey are officially endangered, while the woolly monkey has vulnerable status and the Colombian red howler is classified as declining but of least concern.

Ruscena Wiederholt and Eric Post, of Pennsylvania State University, who conducted the study, said that it highlighted the need for more research into how rising temperatures might affect the ateline primate family, to which all four species belong, and other endangered primates.

They said that their findings were particularly concerning because El Niño was shown to have a negative impact on all four species, even though they were native to different parts of South America.

“Our results indicate that global climate change and increased El Niño events could pose a serious threat to ateline primates,” they wrote in the journal Biology Letters.

“Given that the status of many primate species is already precarious, in the face of continued global change, further studies to quantify the effects of climate and environmental variability on primate species are needed.”

Dr Post said: “El Niño events are expected to increase in frequency with global warming. This study suggests that the consequences of such intensification of the El Niño Southern Oscillation could be devastating for several species of New World monkeys.”

In the study, the scientists examined abundance trends collected by other research groups for four populations of ateline primates: muriquis from Minas Gerais in Brazil, Colombian red howlers from Guarico State in Venezuela, woolly monkeys from Meta in Colombia and Geoffroy’s spider monkeys from Barro Colorado Island in Colombia.

All four species live in social groups and spend most of their time in the trees of tropical forests. Spider and woolly monkeys mainly eat fruit, howlers predominantly eat leaves, while muriquis eat both.

The researchers then investigated how monkey numbers in each population varied from year to year, and compared these with El Niño events. They also used detailed ecological data from Barro Colorado Island, the spider monkeys’ habitat, to track how fruit and leaf abundance varied with the climate.

The results showed that all four monkey species were affected by the El Niño climate cycle. The leaf-eating howler monkeys declined in the year of El Niño events, while those that ate fruit declined in the following year.

Dr Post said that further research would be needed to establish how the El Niño Southern Oscillation and climate change would affect many endangered species.

“Long-term studies like those we derived data from are incredibly valuable for illuminating effects of global warming,” he said. “Unfortunately such studies are also incredibly rare. We hope our results bring attention to the importance of maintaining long-term monitoring efforts.”

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