Small primates have more difficulty with extreme temperatures • Earth.com

On the ‘sky islands’ of South Africa’s Soutpansberg Mountains, two small primate species compete for territory amid a challenging climate.

The first, the fat-tailed galago (Otolemur crassicaudatus), resembles a big cat and is notable for its piercing cries. The second, the southern lesser galago (Galago moholi), is noticeably smaller, with prominent ears and eyes, small enough to nestle comfortably in the hand.

When it comes to climate adaptation, size matters

Michelle Sauther, a primatologist at the University of Colorado Boulder, has focused her research on these species on an important question: How does an animal’s size affect its ability to adapt to extreme temperatures? Her findings indicate that small primate species, such as the lesser galago, may have a harder time as global temperatures continue to rise.

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

Little relief from environmental stress

The experts examined the separate ecosystem within the Lajuma Research Center in the Soutpansberg. This area is known for its diverse flora and sharp temperature swings, ranging from icy winters to summers that reach 100 degrees Fahrenheit.

During their nighttime expeditions, Sauther and her team observed the behavior of both larger and smaller galagos. They noted that the smaller galagos, unlike their larger counterparts, seemed forced to forage continuously regardless of extreme temperatures, so they suffered little from environmental stress.

Consequences of climate change

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

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

“Because you can’t see much at night, you start hearing all these things that you would otherwise never hear: a lot of insects, a lot of animal sounds,” Sauther said. “Every now and then you come across a leopard.”

The findings showed that while larger galagos were more active at moderate temperatures, smaller galagos were observed to be active over a wider temperature range, from as high as 79 degrees Fahrenheit to below 40 degrees Fahrenheit.

This behavioral difference, according to Sauther, is related to metabolic needs. Smaller galagos, due to their small size and fast metabolism, must constantly search for food, while larger galagos have the ability to store more fat, allowing them to rest in less favorable conditions.

Increasing pressure on small primates

Pressure on both species is increasing, with threats from habitat fragmentation and the exotic pet trade, but neither is currently considered endangered.

Sauther hopes this study will lead to further research and awareness of these often overlooked creatures. “We’re concerned about these stealth changes that may be happening in species like this. We hear a lot from people: “I used to see them a lot on my farm, but not anymore,” she concluded.

More about small primates

Small primates, such as tamarins and marmosets, lead dynamic lives that are closely intertwined with the forest ecosystems in which they live. These creatures live primarily in trees and spend most of their time in the treetops, where they adeptly navigate the canopy, jumping and climbing with remarkable agility.

These high perch not only provide safety from ground predators, but also position 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 and consists of fruits, insects and sometimes small vertebrates. This diversity requires a wide range of foraging techniques, from picking fruit and digging for insects to expertly hunting small animals.

Their foraging practices are not only a means of subsistence, but also a way of interacting with their environment, which boosts their cognitive skills and helps maintain their physical health.

Social structures among small primates are equally complex and fascinating. Many species live in close-knit groups that communicate with a rich repertoire of vocalizations, facial expressions and body postures. These groups are critical for mutual protection and rearing of young, with members often participating in the shared care of 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 complex social systems and their active, engaged lifestyles make small primates an important part of their ecological niches, contributing significantly to the biodiversity of their habitats.

The research has been published in the International Journal of Primatology.

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