Taste Discrimination in Lemurs and Other Primates, and the Relationships to Distribution of Plant Allelochemicals in Different Habitats of Madagascar

Abstract

This chapter deals with the adaptation of taste responses of lemurs and other primates to different environments, in relation to primary and secondary compounds in potential foodstuffs. Emphasis is placed on the relationship between taste sensibility to sugars and energy expenditure across species. In the most specialized species, the adaptive trends are inferred according to the importance of the deviation from such allometric relationship. The signification of sugar mimics present in some fruits is discussed in terms of coevolution of plants and tasting ability of primates, that, for lemurs, parallels that of platyrrhine monkeys. Taste responses towards other tastants such as sodium chloride are examined in relation to potential risks of deficiency and/or toxicity. Sensitivity to tannins has been investigated in different species, with a two-bottle preference test. We observed large variations that are likely to be adaptive to the concentrations in plant species in various environments. For instance, the rejection threshold for a mixture of tannin and fructose is much higher in Propithecus verreauxi (above 170 g/l) than in Microcebus murinus (0.54 g/l). Recognition thresholds can also vary slightly between human populations, in relation to ancient or recent food practices. There is also a wide range of taste sensitivity towards quinine, without any correlation, in this case, with body mass or other factors related to energy expenditure. Different habitats of Madagascar are compared according to the results of screening tests on tannins and alkaloids. The eastern rain forest (at Andasibe) present slightly lower proportion of plants with alkaloid-like reaction, and a significantly higher proportion of tannin-rich plants than both the gallery forest and the Didiereaceae bush in the south (at Berenty. The results have been related to the gustatory ability of lemur species having to cope with these secondary compounds, and the food niche of the different species.