Animal semantic communication has received considerable theoretical and emp
irical attention because of its relevance to human language; Advances have
been made by studies of alarm-call behaviour in nonhumans. In monkeys, for
example, there is evidence that recipients have a fairly sophisticated unde
rstanding of a call's meaning; that is, the predator type usually associate
d with a certain alarm call. Little is known, however, about the mental mec
hanisms that drive call production in nonhuman primates. In some nonprimate
species, it has been found that signallers do not respond to a predator's
physical features put instead seem to respond to its relative threat or dir
ection of attack. In these species, therefore, alarm calls do not denote di
fferent predator categories but,simply reflect different types or levels of
danger. Because different predator categories;typically impose-different t
ypes and degrees of threat it is entirely possible that nonhuman primates a
lso respond to threat rather than a predator's category. This study examine
d how wild Diana monkeys, Cercopithecus diana, of the Tai forest, Ivory Coa
st, label predation events. By altering playback stimuli and the position o
f a concealed speaker, I investigated whether Diana monkeys respond with ac
oustically different alarm calls depending on a predator's (1) distance (cl
ose versus far), (2) elevation (above versus below), or (3) category (eagle
versus leopard). Analysis of male and female alarm-call behaviour showed t
hat Diana monkeys consistently responded to predator category regardless of
immediate threat or direction of attack. Data further suggested that, in a
ddition to predator category, monkeys' alarm calls might also convey inform
ation about the predator's distance. (C) 2000 The Association for the Study
of Animal Behaviour.