In Tamil, one of two official languages spoken throughout the northern and eastern parts of Sri Lanka, red slender lorises are referred to by their native name thevangu, which translates to “the slender-bodied one” in English. As their name suggests, slender lorises have long, thin limbs, accompanied by small hands, rounded heads, and pointed muzzles. The tops of their hands, feet, back, and face are covered with a dense layer of short, soft, reddish-tan fur, while their underside is coated with a thinner layer of silver-white fur. In general, like most fun-size creatures, their bodies are very compact!

Among all small mammal species, lorises are considered one of the strongest. In addition to having extremely strong fingers and toes, lorises have specialized muscles and blood vessels in their limbs that allow them to maintain a powerful grip for long, extended periods of time, without fatiguing. To further help with their grip, lorises also have five toes on each foot, including an opposable big toe, that is capable of grasping. Combined, these evolutionary features encourage arboreal survival; without proper grip strength, they would not be able to hang, climb, swing, or access food sources within their environment.

Disproportionate to their small heads, these nocturnal primates have large, saucer-like eyes that appear orange in color. Each eye contains a tapetum lucidum, or reflective layer, that reflects light through the retina, back to the lighting source. In low levels of light, the tapetum lucidum improves their night vision by stimulating light-sensitive cells that turn electrical signals into visual images, evidently allowing them to observe their environment. 

Although their ears are often hidden under their fur, their nighttime navigation is further aided by their extraordinary hearing, especially since they rely heavily on sound for communication and hunting prey.