The gray slender loris is a nocturnal primate that hunts primarily using vision (2) (6), and therefore has remarkable eyes that are adapted to this life. A special layer at the back of the eye reflects light back through the retina, resulting in increased stimulation of the photoreceptors, and allowing vision in very low levels of light (3). The gray slender loris feeds primarily on insects (1), particularly ants, although the gum from trees is also eaten (6). This arboreal species remains in the trees to hunt insects, and adopts acrobatic positions in order to capture its prey (6). With its feet clinging to a branch in a vice-like grip, the gray slender loris can reach up with both arms to snatch an insect from the air, or hang down from the branch to pluck insects from the undergrowth (6). Often, the gray slender loris will silently stalk its prey, before reaching out to grab it, in a hunting manner that has been compared to a cat (6).
Although this species often forages alone (5), it is actually a social primate that sleeps during the day in groups of up to seven individuals (1), and interacts within the group throughout the night; physical contact and grooming are reported to be essential components of slender loris behaviour (5). Each group typically comprises one female, her dependent offspring and one or more males (5). The males, which have home ranges almost twice the size of those of females, act aggressively toward any male from outside their own sleeping group, while adult females rarely interact with each other (5). Females may give birth to twins, twice each year (5); one study revealed that these two births take place during April / May, and October to December after a gestation period of 5.5 months (7).