Anglia Ruskin University: Pressures drive tree-living primates to the ground

A large-scale study of 47 species of monkeys and lemurs has found that climate change and deforestation are driving these mainly tree-dwelling primates to spend more time living on the ground.

The study, published today in the journal Proceedings of the National Academy of Sciences (PNAS), was led by Dr Timothy Eppley of San Diego Zoo Wildlife Alliance. It examined more than 150,000 hours of observation data on 15 lemur species and 32 monkey species at 68 sites in the Americas and Madagascar, and involved experts from institutions around the world, including Anglia Ruskin University (ARU).

Many of the species studied are already burdened with living in increasingly warmer, more fragmented, and more heavily disturbed environments that often have fewer available dietary resources. The study found that primates living in hotter environments, and with less canopy cover, were more likely to adapt to these changes by shifting toward more extensive ground use.

As climate change worsens and arboreal habitats diminish, the study suggests primates consuming a more generalised diet and living in larger groups may more easily adapt. The study found that primates that consume less fruit and live in large social groups are already more likely to adopt a terrestrial lifestyle.

The study also found that primates living closer to human populations are less likely to descend to the ground. The presence of humans, which can be a threat to primates, may therefore interfere with their ability to adapt to global change.

Lead author Dr Timothy Eppley, a postdoctoral associate at San Diego Zoo Wildlife Alliance, said:

“This study began with a discussion among colleagues about how we’d noticed certain populations of arboreal primates spending more time on the ground, yet at sites with relatively less disturbance, members of the same species may never descend to the ground.

“It’s possible that spending more time on the ground may cushion some primates from the effects of forest degradation and climate change; however, for the less-adaptable species, fast and effective conservation strategies will be necessary to ensure their survival.”

Co-author Dr Andrew Smith, Associate Professor in the School of Life Sciences at Anglia Ruskin University (ARU), said:

“As a primatologist, I investigate the behaviour and ecology of small, tree-living monkeys – saddleback and moustached tamarins. My research involves working with tamarins in zoos in the UK as well as in their native rainforest in the Peruvian Amazon.

“I was contacted by Tim Eppley, who was coordinating a large team of primate researchers from around the world to look at what may be influencing the degree to which these tree-living primates use the ground. Together we pooled our field observations to create a unique dataset. This data includes ecological information alongside behavioural observations, and shows that increased use of the ground is linked to rising temperatures and decreasing forest canopy cover.

“As human-caused impacts to habitats and climate worsen, primates are facing unprecedented challenges to survive. Our results suggest that those primates already living in hot, more open forests, and which have more generalised diets are likely to increase their use of the ground, something which may help buffer them against extinction as their climate and habitat continues to change.”

The transition from an arboreal to terrestrial lifestyle has occurred previously in primate evolution, but the researchers believe today’s rapid changes are a serious threat. Dr Giuseppe Donati of Oxford Brookes University, a senior author on the study, added:

“Though similar ecological conditions and species traits may have influenced previous evolutionary shifts of arboreal primates, including hominins, to ground living, it is clear that the current pace of deforestation and climate change puts most primate species in peril.”