Monkeys and lemurs are coming down from the trees as climate warms up

Rising temperatures and deforestation are pushing tree-dwelling primates to spend more time on the ground in search of shade and water

By Madeleine Cuff

Brown howler monkeys

Gabriela Pacheco Hass

Tree-dwelling species of monkeys and lemurs are spending increasing amounts of time on the forest floor as they seek refuge from rising temperatures.

Scientists say the shift from arboreal lifestyles is a “concerning” sign the primates are struggling to survive in forests damaged by human activity and climate change.

The warning follows a study based on more than 150,000 hours of observations of 47 tree-dwelling primate species living across almost 70 sites in Madagascar and the Americas.

Some primates, including howler monkeys (genus Alouatta) and bamboo lemurs (genus Hapalemur), are spending more time on the ground in areas where their forest is degraded and fragmented.

The findings are a signal that these animals are having to adapt their behaviour in response to climate change and habitat loss, says Giuseppe Donati at Oxford Brookes University in the UK, a member of the study team.

He says the animals are being forced to the ground to seek shade and water to recover from rising temperatures higher in the forest canopy.

“In most tropical countries where these species live, humans log the forest,” he says. “This creates gaps and it opens the canopy of the forest. That causes an increase in temperature.

“The deforestation is working together with climate change [to force primates to the ground].”

Southern lesser bamboo lemurs (Hapalemur meridionalis) grazing

Tim Eppley

Donati says he has seen first-hand how bamboo lemurs in Madagascar are now spending around half their waking hours at ground level.

“Those bamboo lemurs usually live in the forest and they are tree-dwelling lemurs,” he says. “But in the south of Madagascar, a very fragmented area, those bamboo lemurs get out of the forest and they graze the grass, a bit like little cows.”

Species that live in large groups and those that eat foods other than fruit are among the most likely to spend more time on the forest floor, the study concluded.

It suggests these more flexible species may be able to partially adapt their lifestyles in response to climate change and habitat loss, at least in the short term.

But Timothy Eppley at the San Diego Zoo Wildlife Alliance, a non-profit organisation based in California, warns arboreal primates can’t adapt quickly enough to keep pace with deforestation and climate change.

“None of the species we studied are likely to fully transition to a terrestrial lifestyle. It’s simply not a viable long-term outcome to happen in such a short period of time,” he says.

“We need to actively protect the forest habitat that we currently have.”

Journal reference: PNAS, DOI: 10.1073/pnas.2121105119

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