Slow lorises are omnivores that feed primarily on tree sap, gum, nectar, fruit, and insects. Their diet leans heavily toward plant exudates, the sticky, sugary fluids that ooze from tree bark. In a field study of the Sunda slow loris in western Malaysia, sap alone made up about 35% of feeding time, with nectar and nectar-producing plant parts adding another 32%, fruit accounting for 23%, and the remaining 11% split between gums and arthropods like insects and spiders.
Tree Sap and Gum Are the Foundation
The single biggest component of a wild slow loris diet is tree exudates: sap and gum. Slow lorises don’t just lick sap that happens to be flowing. They actively gouge into bark with their teeth to get it started. Their lower front teeth form a structure called a toothcomb, and in slow lorises this toothcomb is uniquely built for the job. Compared to their close relatives the slender lorises, slow lorises have toothcombs that are narrower, shorter, and thicker, giving them a stronger ability to withstand the bending forces of scraping into wood.
The pygmy slow loris takes this even further. In one study of reintroduced pygmy lorises, 60% of the diet was gum and other exudates, with insects making up the remaining 40%. No fruit or nectar was recorded in that population at all, highlighting how central tree exudates are to some species.
Nectar Feeding and Pollination
Slow lorises spend a significant chunk of their feeding time on floral nectar. They grip flower clusters, lick the nectar from individual blossoms, and in the process get pollen stuck to their forearms, heads, and bellies. Research on the Bengal slow loris in northeastern Thailand found that they were the most frequent vertebrate visitors to the flowers of a tree called Parkia sumatrana, a legume with large ball-shaped flower heads. Because pollen grains stuck to their bodies during feeding, slow lorises likely serve as pollinators for these plants, a role more commonly associated with bats or insects.
Fruit as a Supplement
Fruit rounds out the diet but isn’t the dominant food source most people assume. In the Malaysian field study, fruit made up roughly 22.5% of feeding time, and the proportions stayed fairly stable across seasons. Slow lorises tend to seek out soft, ripe fruits they can access while moving through the canopy at night. Their slow, deliberate climbing style lets them reach fruit on thin branches that heavier primates can’t access.
Insects, Eggs, and Small Animals
Slow lorises are surprisingly capable hunters. Their trademark slow movement, often seen as a limitation, actually works in their favor when stalking prey. They creep close to insects, small birds, lizards, and eggs, then snatch them with a quick grab. Insects appear to be the most common animal prey, but slow lorises will take vertebrates when the opportunity arises. For the pygmy slow loris, insects can represent up to 40% of the diet, making animal protein a major nutritional source rather than a rare treat.
Foraging Takes Up Most of the Night
Slow lorises are strictly nocturnal, and foraging and traveling together fill nearly half of their active hours each night. They move through the forest canopy methodically, visiting known gum-producing trees, checking flower clusters for nectar, and scanning branches for insects. Their pace is slow but persistent. This energy-conservative strategy pairs well with a diet built around tree exudates, which are reliable and stationary food sources that reward routine visits over long-distance searching.
Why Captive Diets Often Go Wrong
In captivity, slow lorises are frequently fed diets heavy in fruit and commercial foods, which is a poor match for their natural intake. The consequences are serious. Long-term fruit-heavy diets with too few plant exudates lead to oral diseases, likely because the sugar profile of fruit differs from the complex carbohydrates in gum and sap that their teeth and digestive systems evolved to handle. Incorrect diets also raise mortality rates among captive individuals and reduce the chances of survival for those reintroduced to the wild.
Research on rescued Bengal slow lorises has shown that shifting from a captive fruit-based diet to one that better mimics wild feeding patterns changes the gut microbiome substantially. The mismatch between what slow lorises eat in the wild and what they’re offered in captivity is one of the central challenges in their conservation and rehabilitation.
A Possible Link Between Diet and Venom
Slow lorises are one of the only venomous primates. They produce a toxic secretion from glands on the insides of their upper arms, which they mix with saliva to deliver a painful, sometimes dangerous bite. Researchers have identified over 200 different compounds in this secretion, many of them aromatic chemicals that appear consistent with dietary absorption. This raises the possibility that slow lorises sequester defensive chemicals from certain foods they eat, though the connection hasn’t been fully confirmed. What is clear is that captive slow lorises on simplified diets produce a different chemical profile than wild ones, suggesting diet plays some role in the composition of their venom.