Ground instead of treetops: moving down one floor when it gets too hot upstairs or there is a lack of forest – can primates do that? A large research team has investigated this question.
San Diego – The climate crisis and global deforestation are driving lemurs and other arboreal primate species to the ground. This is the report of the authors of a broad study published in the journal Proceedings of the National Academy of Sciences (PNAS). The change of habitat can save the animals from extinction – however, such an adaptation is not possible for all species.
“The study began with a discussion among colleagues who had noticed that certain populations of arboreal primates spend more time on the ground,” recalls biologist and lead author Timothy Eppley of the San Diego Zoo Wildlife Alliance. As a result, 118 scientists from 124 institutions began to work together. They collected more than 150,000 hours of observational data on 15 lemur and 32 monkey species at 68 sites in America and Madagascar. All primate species studied are considered to be predominantly arboreal.
The researchers estimated how factors such as human influences and species-specific traits affect how much time the primates spent on the ground. Data analysis revealed differences both between and within species.
Search for food and refreshment
Species that eat less fruit, have a broader diet, and live in large social groups are more likely to land. The researchers assume that they find more food here, while the larger group size offers better protection against potential enemies. Especially in hotter regions, where the treetops are getting lighter, the animals could also flee from the heat down below.
“For example, we found that primate species such as Eulemur fulvus and Eulemur rufifrons spent significantly more time on the ground in the relatively hot tropical deciduous forests of Madagascar than their counterparts in the cooler humid forests, likely to access terrestrial water sources,” it says in the study. This could mean a potential pre-adaptation to life on the ground.
“It’s conceivable that more time on the ground protects some primates from the effects of forest degradation and climate change,” says study leader Eppley. However, such an adaptive behavior might not be possible for all primates: “However, fast and effective protection strategies are required for the less adaptable species in order to ensure their survival.”
Humans interfere with adaptability
The study also found that primate populations that are close to human infrastructure are less likely to climb down from trees. “This result could indicate that the presence of humans, which often poses a threat to primates, is affecting the natural adaptability of species to climate change,” explains biologist Luca Santini of Italy’s Sapienza University.
In principle, there have been several transitions from an arboreal to a terrestrial way of life in the evolution of primates. However, today’s rapid changes pose a serious threat, points out Giuseppe Donati of Oxford Brookes University, another author of the study. “Although similar ecological conditions and species traits may have influenced previous evolutionary shifts of arboreal primates, including hominins, to terrestrial lifestyles, it is clear that the current pace of deforestation and climate change is putting most primate species at risk.”
