Padrões de forrageio da formiga-cortadeira-de-folha atta laevigata (formicidae, attini) em uma área de cerrado

Abstract

Ants have a circadian foraging rhythm, which can be modified according to the colony's nutritional needs or environmental conditions. In most of the Brazilian Savanna, the climate is strongly seasonal, with temperature and precipitation showing great variation between the dry and rainy seasons, and it is known that temperature is the climate variable most frequently correlated with changes in foraging patterns. there is also some relationship to humidity, atmospheric pressure and precipitation. The present study aimed to determine: i) the circadian rhythm presented by de Atta laevigata in the Brazilian Savanna; ii) whether the pace can change seasonally; iii) whether environmental factors (such as temperature, humidity and precipitation) can explain the observed patterns and occasional seasonal changes, and it was sought to iv) determine whether the quantity and quality of plant material collected by the colonies can also vary seasonally; and vi) to analyze the efficiency of the collection of fragments against the activity of 10 colonies of A. laevigata in an area of cerrado restricted sense, monitored for 18 months at intervals of 3 h for 24 hours. Ants were more active at night with temperatures between 15 and 25º C and relative humidity between 70 and 90%, and almost non-existent activity below 14 and above 35º C. They presented three patterns of circadian cycles (nocturnal, diurnal and mixed) that change throughout the year between the colonies and in a synchronized way. Changes in cycles occurred in three periods under the influence of environmental factors and intrinsic to the colonies. The foraging rate is greater in the transition from dry to rainy seasons, with an average efficiency rate of 25%. The types of plant material vary throughout the year, with leaves, flowers and dry material being the most collected items. This study provided more concrete information about the foraging pattern that A. laevigata presents in a cerrado phytophysiognomy, making it possible to better assess its impact on this ecosystem.