RELATIVE EFFICIENCY OF PREFERRED AND NONPREFERRED PATTERNS OF LATERALIZED FORAGING IN THE GENTLE LEMUR (HAPALEMUR GRISEUS)

Lateralized patterns of hand use in species-typical bamboo shoot forag ing were evaluated for efficiency in five female and six male gentle l emurs (Hapalemur griseus sp.). Efficiency was defined as amount of tim e required to complete a foraging response sequence. The foraging patt ern consisted of four component movements: PULL-IN, COUNTERFORCE, TURN , and FEED-IN. These component movements had been shown in a previous study to incorporate lateral hand biases that formed subsets of patter ns that were characteristic for each gentle lemur. The duration of eac h foraging sequence was measured from the beginning of the first compo nent to the initiation of the terminal component. Frequency of use sco res were employed to divide the pattern sequences of each subject into preferred and nonpreferred categories. A within-subjects comparison o f the mean durations of preferred patterns (M = 2.56 sec) with those o f nonpreferred patterns (M = 3.02 sec) found that preferred patterns w ere executed more rapidly, t(10) = 3.36, P = .007. A multiple regressi on showed that order of pattern preference accounted for 89% of the va riance in mean duration of response time (R(2) = .89, P = .056). Thus, the use of preferred lateralized hand patterns resulted in more rapid bamboo shoot harvesting. Speed in foraging may be regarded as an adap tive strategy for a species that subsists on a high bulk, low nutrient density food such as bamboo. (C) 1995 Wiley-Liss, Inc.