of females. In the absence of direct studies of the genus, primatologist Simon Bearder speculated that slow loris social behavior is similar to that of the potto, another nocturnal primate. Such a social system is distinguished by a lack of matriarchy and by factors that allow the slow loris to remain inconspicuous and minimize energy expenditure. Vocal exchanges and alarm calls are limited; scent marking with urine is the dominant form of communication. Adult males are highly territorial and are aggressive towards other males. Vocalizations include an affiliative (friendly) call krik, and a louder call resembling a crow's caw. When disturbed, slow lorises can also produce a low buzzing hiss or growl. To make contact with other individuals, they emit a single high-pitched rising tone, and females use a high whistle when in estrus. Slow lorises are slow and deliberate climbers, and often hold on to branches with three of their four limbs. To move between trees, they carefully grip the terminal branches of the neighboring tree and pull themselves across the small gap. They will also grip branches with only their hind feet, lift themselves upright, and quickly launch forward with their hands to catch prey. Due to their slow movement, all lorises, including the slow lorises, have a specially adapted mechanism for defense against predation. Their slow, deliberate movement hardly disturbs the vegetation and is almost completely silent. Once disturbed, they immediately stop moving and remain motionless. In Indonesia, slow lorises are called malu malu or "shy one" because they freeze and cover their face when spotted. If cornered, they may adopt a defensive posture by curling up and lunging at the predator. The Acehnese name, buah angin ("wind monkey"), refers to their ability to "fleetingly but silently escape". Little is known about the predation of slow lorises. Documented predators include snakes, the changeable hawk-eagle (Nisaetus cirrhatus), and Sumatran orangutans (Pongo abelii). Other potential predators include cats, sun bears (Helarctos malayanus), binturongs (Arctictis binturong), and Asian palm civets. Slow lorises produce a secretion from their brachial gland (a scent gland on the upper arm near the axilla) that is licked and mixed with their saliva. In tests, three predators—binturongs, clouded leopards (Neofelis nebulosa), and sun bears—retreated or showed other signs of displeasure when presented with cotton swabs anointed with a mixture of the toxic secretion and the saliva, whereas the toxic secretion alone generated mild interest. Before stashing