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Rhythmic Foraging in the Leaf-Cutting Ant Atta cephalotes (L.) (Formicidae: Attini)

1974; Wiley; Volume: 43; Issue: 1 Linguagem: Inglês

10.2307/3162

1365-2656

Theodore Lewis, G. V. Pollard, G. C. Dibley,

Neurobiology and Insect Physiology Research

The foraging behaviour of leaf-cutting ants can be divided into three broad aspects; namely, the spatial distribution of foraging around nests, the type and amount of vegetation collected by foragers, and the timing of activity during each 24-h cycle. The first two topics have been studied extensively for Atta cephalotes (L.) in tropical forest (Cherrett 1968, 1972) and in laboratory tests (Barrer & Cherrett 1972), and fairly consistent patterns of behaviour established. By contrast, the accounts of rhythmic foraging are confusing, the ants apparently behaving inconsistently. For example, in different parts of South and Central America, Beebe (1921), Weber (1941, 1946) and Cherrett (1968) recorded predominantly nocturnal foraging, whereas Lutz (1929) and Hodgson (1955) observed foraging only in daylight; in Trinidad, Panama and Belize we have seen this species foraging by both day and night. The most striking feature of foraging from day to day is its rhythmic sequence. A particular nest observed at the same time in each 24-h (diel) period usually shows a similar degree of foraging activity for weeks, or even months, at a time. Because most of the observations made hitherto have lasted only a few days or weeks the diel rhythms of the individual nests studied have appeared fairly regular. But over longer periods of time the rhythms change, often quite suddenly and inexplicably, so that a nest which has foraged during daylight for several months reverts to foraging at night and vice versa. Nests within a few hundred metres of each other may forage at the same or at different times within a 24-h period; over a wider area of several thousand hectares some nests can usually be found foraging whatever the time of day or night, although each has its own distinct rhythm. The main object of this paper, considered in Part II, is to describe the collective aspects of foraging, especially diel and long-term rhythms, to see whether the ants' characteristic cyclical behaviour depends on widespread physical changes in their environment. But, as a background to the study of collective rhythms, Part I of the paper describes individual aspects of behaviour showing how far, how rapidly, and how often foraging ants walk along their trails, and the role of different individuals on the trail.