If you were to picture a monkey, you might imagine a medium-sized body, brown fur, a long tail, and, of course, an animal swinging through the trees. Most monkeys are considered to be arboreal, or tree-dwelling and the fact that humans predominantly walk on land is actually a major part of primate evolution, and there is lots of research that investigates the transition from tree-dwelling to land-dwelling.
But, new research suggests that climate change may actually be driving many monkey species from the trees to the ground. With the rise in temperatures, arboreal monkeys are spending more time on the ground than they used to previously.
Warming temperatures impacts other ecological factors such as fruit availability. If there is less canopy coverage and less food, monkeys are likely to explore other avenues to both stay cool and eat. For monkeys that already eat a relatively generalized diet, the transition is easier than it would be if they relied on a very specific food source. Shifting to a more terrestrial lifestyle comes with other risks such as increased predation, and increased risk due to anthropogenic factors (e.g., proximity to roads, human population density). In turn, this is causing a shift to smaller group sizes.
The current study, led by Timothy Eppley from the San Diego Zoo Wildlife Alliance and Portland State University, observed 47 different arboreal primate species and found that some species in particular—like howler monkeys and bamboo lemurs—spend more time on the ground when the forest is fragmented. The bamboo lemurs are now spending half of their time on the ground, usually grazing grass when they can’t get enough fruit in trees.
The change in climate in these habitats is most likely due to human activity—logging creates gaps in the forest canopy which increases temperature in that area. Unsurprisingly, climate change continues to affect non-human species, and recent reports from the United Nations suggest drastic measures must be taken to mitigate the effects. While these primates are unlikely to transition to a fully terrestrial lifestyle, this study found that more flexible species are able to alter their behaviors when necessary for survival.