Horsfield’s tarsier is extremely agile and almost entirely arboreal (5). The tarsier’s limbs have a number of adaptations for life in the trees, including a unique arrangement of bones in the heel and powerful muscles in the legs which make up almost a quarter of the weight of the entire body (4). As a result, Horsfield’s tarsier is able to leap effortlessly between trees and shrubs, and will cling with ease to vertical objects by rigidly applying its tail for support and grasping with its well-adapted limbs (1) (5). Horsfield’s tarsier is capable of leaping over five metres (4), which is almost 40 times its own body length (2).
Horsfield’s tarsier is nocturnal (1) (4) (5) (7), spending much of the day sleeping in dense vegetation on a vertical branch, or occasionally in a hollow tree (5). Although Horsfield’s tarsier rarely moves on the ground, many of this species’ activities, such as foraging and sleeping, are usually done within two metres of the ground (1) (7).
Tarsiers are the only entirely carnivorous primates (1) (2) (4). Although Horsfield's tarsier may make frequent, high-pitched calls as it searches for insects, it generally forages for food alone (7). A wide variety of insects are taken, including beetles, grasshoppers, cockroaches, locusts, butterflies, moths, ants and cicadas (1) (2) (4). Horsfield’s tarsier will also take small vertebrates, such as birds, bats, frogs and snakes (1) (2). This species captures its prey by reaching and grabbing it while remaining stationary on a vertical branch, or by leaping onto or towards it (4). In general, tarsiers will eat around 10 percent of their own body weight every 24 hours (2).
Horsfield’s tarsier becomes sexually mature at around a year old, although a young male may sometimes delay reproductive maturity until it is able to establish its own home range. Courtship is usually a rather energetic affair, with much chasing around, often accompanied by soft vocalisations (2).
Breeding occurs throughout the year. The gestation period of Horsfield’s tarsier is around 178 to 190 days (2) (5), which is an unusually long period for such a small mammal (5). The single young is born with its eyes open and a full coat of fur (2) (5). It is able to climb at just a day old (2), but it is around a month before it is able to leap between trees and shrubs (5). The young Horsfield’s tarsier usually clings to the female’s belly until it is weaned, which occurs shortly after it begins to capture its own prey at around 42 days old (5).
Horsfield’s tarsier is territorial, with pairs usually occupying a small home range. The pair will scent mark the territory with urine and a secretion from a gland on the chest (2) (5), and will actively chase and shriek loudly at intruders (5).