PLAY AS INDICATOR OF HABITAT QUALITY - A FIELD-STUDY OF LANGUR MONKEYS (PRESBYTIS-ENTELLUS)

The ecology and social behavior of two male bands of Hanuman langurs ( Presbytis entellus) of similar size and age-class composition were stu died over 18 mo in Rajasthan, Northwest India. Play behaviour was test ed as a reflection of environmental conditions. One of the bands lived in a poor habitat where food and water was often scarce, the other in a rich habitat with relatively abundant resources. For example, the p roportion of fruit eaten was much higher for the rich-habitat monkeys (RHM), whereas more than half of the diet of the poor-habitat monkeys (PHM) consisted of leaves. The frequency of play-lighting and locomoto r-rotational play correlated negatively with the amount of leaves eate n, probably because they are low in energy. Consequently, play rates f or the RHM were not only 6-7 times higher than for the PHM, but play a lso lasted significantly longer. Play rates among PHM were reduced to zero during adverse environmental conditions but showed a dramatic inc rease when more plant food became available as a result of monsoon rai ns. The data provide considerable support for the hypothesis that play is a sensitive indicator of habitat quality.