Influence of colour vision on feeding behaviour and leadership in groups of Callithrix jacchus in an area of Caatinga
Visual polymorphism; frugivory; insectivory.
Primates are unique among mammals because they can be trichromates. However, while in catarrhines (Old World primates) both males and females present both trichromatic vision, in platyrrhines (New World primates) there is colour vision polymorphism, with occurrence of heterozygous females (i.e. trichromates), as well as, hemizygous males and homozygous females (i.e. dichromates). In what concerns feeding behavior, it is believed that trichromacy is an adaptation to improve foraging efficiency, namely, to improve the detection of mature fruits and / or young leaves against the mature leaves of the background. On the other hand, it has been suggested that trichromacy is not always advantageous, more specifically, dichromate individuals would find more camouflaged insects. Another important relation between colour vision and primate behaviour would be its influence on leadership during group movements, since the group leader is more likely to reach food sources first and can control the quality of the food source and the type of food. In fact, some studies show that females lead the group more often than males, influencing their foraging efficiency and feed rate. Considering these questions, we will analyze if the colour vision influences the foraging efficiency and the leadership during group movements of Callithrix jacchus in the Caatinga. For this, two groups will be observed in the Assu National Forest, from dawn to dusk, where each individual will be observed for two hours and the number of food items consumed, type of food (fruit, gum and insects), colour and type of substrate will be recorded, as well as, the position of the focal individual during group movements. During the year of observations, the fruits availability and arthropods abundance in the area used by both groups will be evaluated and the reflectance spectrum of the items consumed will be measured with the spectrophotometer to compare the detection ability of items among the phenotypes.