Small primates struggle more with extreme temperatures

In the “sky islands” of the Soutpansberg Mountains in South Africa, two small species of primates vie for territory amidst a challenging climate. 

The first, the thick-tailed greater galago (Otolemur crassicaudatus), resembles a sizable cat and is notable for its piercing cries. The second, the southern lesser galago (Galago moholi), is notably smaller, with prominent ears and eyes, small enough to nestle comfortably in one’s hand.

When it comes to climate adaptation, size matters

Michelle Sauther, a primatologist at the University of Colorado Boulder, has delved into an important question through her research on these species: How does an animal’s size influence its ability to adapt to extreme temperatures? Her findings indicate that small primate species, such as the lesser galago, might struggle more as global temperatures continue to rise.

“Body size really does affect everything,” Sauther said. “How big you are affects your life history. It affects when you reproduce. It affects how long you live.”

Little relief from environmental stresses 

The experts examined the distinct ecosystem within the Lajuma Research Center in the Soutpansberg Mountains. This area is known for its diverse flora and sharp temperature fluctuations, ranging from frosty winters to summers that soar to 100 degrees Fahrenheit.

During their nighttime expeditions, Sauther and her team observed the behavior of both greater and lesser galagos. They noted that the lesser galagos, unlike their larger counterparts, seemed compelled to forage continuously, regardless of extreme temperatures, leaving them little relief from environmental stresses.

Implications of climate change

“In conservation, we tend to focus a lot on lemurs, gorillas, chimpanzees,” Sauther said. “But we also have to think about the implications of climate change for these smaller and nocturnal species, which most people don’t know much about.”

The scientists’ method involved nocturnal walks through the reserve over the course of a year, totaling 75 nights. They used red lights to spot the reflective eyes of galagos and thermal imaging to study them in their arboreal habitat.

“At night, because you can’t see much, you start hearing all these things that you just would never hear otherwise – a lot of insects, a lot of animal calls,” Sauther said. “Once in a while, you’ll run into a leopard.”

Metabolic needs of small primates 

The findings revealed that while greater galagos were more active during moderate temperatures, lesser galagos were observed to be active across a broader range of temperatures, from as high as 79 degrees Fahrenheit to below 40 degrees Fahrenheit.

This behavioral difference, Sauther believes, is tied to metabolic needs. Lesser galagos, due to their small size and fast metabolism, must continuously seek food, whereas greater galagos have the capacity to store more fat, allowing them to rest during less favorable conditions.

Increasing pressures on small primates 

The pressures on both species are increasing, with threats from habitat fragmentation and the exotic pet trade, yet neither is currently recognized as endangered.

Sauther hopes that this study will prompt further research and awareness of these often-overlooked creatures. “We’re worried about these stealth changes that may be happening among species like these. We hear a lot from people, ‘I used to see them a lot on my farm, but now I don’t,” she concluded.

More about small primates 

Small primates, such as tamarins and marmosets, lead dynamic lives deeply intertwined with the forest ecosystems they inhabit. These creatures are predominantly arboreal, spending most of their time in the treetops where they adeptly navigate the canopy, leaping and climbing with remarkable agility. 

This high perch not only offers safety from ground-based predators but also positions them well to exploit the rich resources available above the forest floor.

Diet and foraging

The diet of these small primates is varied and opportunistic, consisting of fruits, insects, and sometimes small vertebrates. This diversity necessitates a wide range of foraging techniques, from picking fruits and digging for insects to skillful hunting of small animals. 

Their foraging practices are not just a means of sustenance but also a way of interacting with their environment, which stimulates their cognitive abilities and helps maintain their physical health.

Social lives

Social structures among small primates are equally complex and fascinating. Many species live in tight-knit groups that communicate with a rich repertoire of vocalizations, facial expressions, and body postures. These groups are critical for mutual protection and the rearing of young, with members often participating in cooperative care of the offspring.

Living in such groups also requires and reinforces complex social behaviors, including alliance formation, conflict resolution, and social learning, which are essential for survival in the often harsh and competitive environment of the wild. 

These intricate social systems and their active, engaged lifestyles make small primates key components of their ecological niches, contributing significantly to the biodiversity of their habitats.

The study is published in the International Journal of Primatology.

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