Diet and Spatial Pattern of Foraging in Ectatomma opaciventre ...

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