SEED-BREAKING FORCES EXERTED BY ORANGUTANS WITH THEIR TEETH IN CAPTIVITY AND A NEW TECHNIQUE FOR ESTIMATING FORCES PRODUCED IN THE WILD

Citation
Pw. Lucas et al., SEED-BREAKING FORCES EXERTED BY ORANGUTANS WITH THEIR TEETH IN CAPTIVITY AND A NEW TECHNIQUE FOR ESTIMATING FORCES PRODUCED IN THE WILD, American journal of physical anthropology, 94(3), 1994, pp. 365-378
Citations number
50
Categorie Soggetti
Anthropology,"Art & Humanities General",Mathematics,"Biology Miscellaneous
ISSN journal
00029483
Volume
94
Issue
3
Year of publication
1994
Pages
365 - 378
Database
ISI
SICI code
0002-9483(1994)94:3<365:SFEBOW>2.0.ZU;2-M
Abstract
Orang-utans (Pongo pygmaeus) at the Singapore Zoological Gardens were presented with two thick-shelled edible seeds, Mezzettia parviflora (A nnonaceae) and Macadamia ternifolia (Proteaceae) in order to estimate their maximum bite forces. The orang-utans could break the Macadamia s eeds in one bite, while those of Mezzettia required repeated attempts. Examination of shell fragments showed that many had scratches and som e had clear, but small (ca. 1-2 mm diameter), impressions on them. Bui lding upon this information, semi-imitative tests were performed on th e seeds in a universal testing machine by loading them in compression with either flat plates or metal casts of orang-utan cheek teeth. The maximum forces required to break the seeds were similar with both the flat plates and the metal teeth; the average for the Macadamia seeds b eing about 2,000 N (which forms a minimum estimate for the maximum bit e forces in orang-utans) and for the Mezzettia seeds, 6,000 N. The wor k done with the metal teeth was much greater than with the plates. A m echanical analysis showed that this extra work went into producing per manent impressions (''bite marks'') in the shell with the tooth cusps. These impressions were larger than those found on the shells of seeds bitten by the orang-utans. Nevertheless, it is shown theoretically th at the size of these indentations can give an estimate of the bite for ces used. The maximum force developed in the machine tests with the me tal teeth was correlated with the force calculated from analysis of th e bite marks. The method is suitable for use in field studies where th e marks left on remnants of hard foods eaten by primates may be used t o estimate, very roughly, the forces used to produce them. (C) 1994 Wi ley-Liss, Inc.