Diet and Spatial Pattern of Foraging in Ectatomma opaciventre ...
Diet and Spatial Pattern of Foraging in Ectatomma opaciventre ...
Diet and Spatial Pattern of Foraging in Ectatomma opaciventre ...
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T<strong>of</strong>olo, V.C. et al. — <strong>Spatial</strong> <strong>Pattern</strong> <strong>of</strong> <strong>Forag<strong>in</strong>g</strong> <strong>in</strong> E. <strong>opaciventre</strong><br />
The forag<strong>in</strong>g trails presented a s<strong>in</strong>uous pattern from the beg<strong>in</strong>n<strong>in</strong>g to the end,<br />
with directional fidelity (Fig. 2). The pathways from nest 1 were concentrated<br />
around the nest along the north-south axis; <strong>in</strong> nest 2, they were distributed<br />
southeast <strong>and</strong> northwest to the nest; <strong>and</strong> <strong>in</strong> nest 3, they were west-oriented.<br />
Thus, the foragers were spatially distributed <strong>in</strong> the forag<strong>in</strong>g area so as to avoid<br />
overlap with the trails from neighbor<strong>in</strong>g colonies. These areas were explored<br />
repeatedly, demonstrat<strong>in</strong>g the preference <strong>of</strong> colonies for specific regions <strong>in</strong><br />
the forag<strong>in</strong>g arena. In the 3 colonies, most trajectories were close to the nest,<br />
with few pathways more than two meters away from it.<br />
<strong>Diet</strong> <strong>and</strong> forag<strong>in</strong>g effort<br />
Dur<strong>in</strong>g the observation period, few foragers left the nest <strong>in</strong> search <strong>of</strong> food<br />
resources. The workers <strong>of</strong> E. <strong>opaciventre</strong> left the nest on average 5.4 ± 2.7 (SD)<br />
times per forag<strong>in</strong>g hour, return<strong>in</strong>g almost at the same rate, 4.9 ± 2.5 (SD)<br />
times. Of the 371 forag<strong>in</strong>g trips recorded, only 9.16% ended with the workers<br />
return<strong>in</strong>g with prey. Liquid food was not observed <strong>in</strong> the m<strong>and</strong>ibles <strong>of</strong> the<br />
foragers, only solids. The description <strong>of</strong> the prey captured is shown <strong>in</strong> Table<br />
2. Over half <strong>of</strong> the prey items collected (52.78%) belonged to Formicidae,<br />
<strong>in</strong>clud<strong>in</strong>g an <strong>in</strong>dividual <strong>of</strong> the same genus, E. brunneum. All the prey were<br />
collected <strong>in</strong>dividually except a chrysalis <strong>of</strong> Lepidoptera for which there was a<br />
recruitment strategy known as social facilitation. In this event, an <strong>in</strong>dividual<br />
recruited a nestmate to collect the prey item without us<strong>in</strong>g a scent trail. As<br />
the prey was too large <strong>and</strong> fixed to the substrate by silk threads, the forager<br />
quickly returned to the nest <strong>and</strong> then left, followed by another ant. The<br />
recruited ant followed the recruiter to the food source <strong>and</strong> both cut the silk<br />
threads to collect <strong>and</strong> transport the food item to the nest.<br />
DISCUSSION<br />
The diet <strong>of</strong> E. <strong>opaciventre</strong> was narrow, probably because the nests were<br />
located <strong>in</strong> a degraded area <strong>and</strong> the research was carried out <strong>in</strong> the dry season.<br />
In the Brazilian savannah (Cerrado), Pie (2004) observed that, <strong>in</strong> 50% <strong>of</strong> the<br />
cases, the diet <strong>of</strong> E. <strong>opaciventre</strong> is composed <strong>of</strong> termites, <strong>and</strong> over 20% <strong>of</strong> the<br />
other prey consists <strong>of</strong> other ants, ma<strong>in</strong>ly those <strong>of</strong> the genus Atta.<br />
Wheeler (1986) analyzed the diet <strong>of</strong> E. tuberculatum <strong>in</strong> Panama, also us<strong>in</strong>g<br />
the method <strong>of</strong> collect<strong>in</strong>g prey items that workers carried to the nest. Insects<br />
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