More than 100 scientists who spent about 151,000 hours observing animals across Madagascar and Central and South America found that primates risk exposure to new predators to escape the heat and find food, even though they still spend the vast majority of their time in trees.
Those species that are more inclined to adapt to spending time on the ground — whether because they have a more diverse diet, because they live in the relative safety of large groups or are physiologically better able to walk the forest floor — are more likely to descend from trees, Tim said. Epley, a postdoctoral fellow at the San Diego Zoo Wildlife Alliance, said it may be more likely to survive in the future. Epley is the lead author of the study, which was published in the Proceedings of the National Academy of Sciences.
With the acceleration of global warming and the spread of deforestation and wildfires, those primates least privileged to such a transformation will be increasingly vulnerable.
“They won’t be able to live for long,” Epley said. This can exacerbate environmental challenges in vulnerable forest habitats, because animals such as lemurs play an important role in dispersing tree seeds. “Once you get rid of the lemur, there’s this full chain effect.”
The scientists said the research shows signs of hope in the resilience of vulnerable organisms and ecosystems, while also emphasizing the need to slow or prevent warming and Habitat loss.
“The primates of Madagascar are already the most threatened in the world, but studies like this show us that they may be able to find refuge from the worst of climate change by adapting flexibly while spending more time in areas with lower temperatures,” Amanda Korsjens, Professor Behavioral Ecology at Bournemouth University in the UK in an email. “But the study also highlights the importance of maintaining healthy forest habitats to allow primates to use the limited options available to them to manage global warming.”
Helen Slater, a research associate at Newcastle University in the UK, said the study points to a “very daunting task” to predict how different primate species will respond to climate change, and to determine how best to promote their conservation.
“There is not going to be a one-size-fits-all solution, and we will probably have to develop site- and species-specific strategies,” she said in an email.
The research began with Epley’s own observations. He spent a year observing southern bamboo lemurs in southeastern Madagascar and collecting data on their nutrition. He was surprised to discover that in degraded forest habitats, the animals were willing to risk their lives to go down to the forest floor, where they gather more nutritious food and sometimes even sleep. In a healthy, continuous rainforest, Epley said, lemurs can “almost always” be found in trees or bamboo booths.
Then, a discussion at a 2016 conference about his observations and questions, shared by other researchers, became the genesis of the study. Epley began calling anyone he could find who had spent time tracking primates, eventually reaching out to 118 co-authors at 124 different institutions. The study is based entirely on preliminary observations of monkeys and lemurs, as opposed to analysis of a sample taken beginning in 1985.
The study came to different conclusions about what makes primates more likely to leave their natural habitat in trees. Those who live in large groups can come down to earth more often because there is security in numbers, and those willing and able can eat more than just fruit. The warmer the climate and the scattering of tree cover in any given location, the more likely the animals will descend to the ground.
The study found that in areas close to roads and other human infrastructure, primates were less likely to spend time on the forest floor, possibly because that often means proximity to stray dogs.
Researchers not involved in the study said it supports the literature that has shown the effects of climate change on primates, including that primates will increasingly rely on the availability of shade in forests as global temperatures rise, according to Kristjens.
The researchers said more investigations are needed to analyze in detail what is driving the changes in primates’ habits. For example, comparing temperatures on the ground versus in the canopy at monitoring sites can better explain the role higher temperatures play, Slater said.
It is not clear how significant the variability is in the long-term ability of primates to adapt to terrestrial habitats. The study found that of the 15 species of lemur and 32 species of monkey that were observed, they spent less than 5 percent of their time on land, on average, a level low enough that Korstjens wondered how important the habit was to primate survival.
It’s not safe to assume that some species will thrive simply because they may be better able to adapt to spending time on land, said Andrew Bernard, a doctoral candidate in anthropology at the University of Michigan whose research focuses on primate behavior.
“Many primates spend too much time in low-quality habitats that cannot independently sustain viable groups,” he said.
But the study still emphasizes the effects of global warming on animals, and the adaptations it requires of them.
The study focused on primates in Madagascar and the Americas because similar species in Africa and Asia already underwent similar transformations millions of years ago, adapting from living primarily in trees to spending time on land. It’s a relatively common evolutionary transition among primates, although what the researchers observed appears to be different.
“What we’re seeing now is very much man-made,” Epley said. “This happens quickly.”