Role of experience in the development of foraging skills of lambs browsing the shrub serviceberry

Abstract

We studied the development of foraging skills in lambs to better understand why sheep foraging in an unfamiliar environment ingest less forage per unit time than sheep familiar with the environment. We hypothesized that inexperienced sheep are less efficient foragers, in part, because they lack the skills necessary to efficiently prehend and ingest forage. Twenty twin lambs were assigned to either a treatment (experienced) or a control (inexperienced) group. Experienced lambs received 15 times more exposure to the shrub Amelanchier' alnifolia than inexperienced lambs. This experimental design allowed us to test three predictions that stem from our hypothesis. Prediction 1: experienced lambs harvest forage more efficiently than do inexperienced lambs as forage becomes more difficult to harvest. Our results showed that inexperienced vs. experienced lambs did not differ in ability to ingest pelleted (38 vs. 36 g min −1) or chopped (6.7 vs. 7.4 g min −1) shrub, but experienced lambs were more efficient ( P < 0.05) at foraging from entire plants (4.1 vs. 4.7 g min −1) in pen trials of 2-min duration on two occasions. Prediction 2: experienced lambs ingest forage more quickly than inexperienced lambs. We found that the intake rate of experienced lambs was higher ( P < 0.05) than for inexperienced lambs (5.0 vs. 4.3 g min −1) in pasture trials of 5-min duration on two occasions. Inexperienced lambs took larger ( P < 0.05) bites (0.20 vs. 0.16 g per bite), but this did not compensate for the lack of prehension skill. Prediction 3: experienced lambs have better developed prehension skills than inexperienced lambs. We found that although both groups used similar prehension patterns during pasture trials, inexperienced lambs were less ( P < 0.05) successful than experienced lambs at obtaining food by breaking twigs (56% vs. 77% success), stripping leaves (65% vs. 77% success) and plucking individual leaves (81% vs. 89% success).