A Day in the Life of the Giant Ant Dinoponera lucida Emery , 1901 ( Hymenoptera , Formicidae ) : Records of Activities and Intraspecific Interactions

Ants are among the most abundant groups of terrestrial invertebrates. Ants have a wide variety of nesting sites, feeding habits, and trophic interactions (Kaspari, 2000), and are the subject of basic and applied research. However, the biology of most species remains unknown, urging descriptive studies (Krell, 2004; Greene, 2005). Dinoponera lucida Emery, 1901 is a poneromorph ant endemic to the Atlantic Forest (Peixoto et al., 2010; Simon et al., 2020), endangered (EN) according to the Brazilian Red List (MMA, 2014; ICMBio, 2018). Dinoponera lucida is a forest-specialist solitary forager with no recruitment, a typical Abstract Ants present a wide variety of nesting sites, feeding habits, and trophic interactions, but the biology of most species remains unknown. Dinoponera lucida is a poneromorph ant forest-specialist and solitary forager, endemic to the Brazil’s Atlantic Forest. Herein we describe foraging activities, guard and maintenance of the nests, orientation mode, and intraspecific interactions performed by D. lucida. We found three nests distant from each other at least 8.5 m, and the mean reached distance by a worker was 3.8 m. The workers showed colony fidelity and random forage in their territory. We observed two non-agonistic interactions between workers from the same nest, and two agonistic interactions between foraging workers from different nests. The low frequency of agonistic interactions suggests that workers from different nests are unlikely to forage in the same area. Our results expand the knowledge on ants’ natural history through data on foraging activities, guard and maintenance of the nests, orientation mode and intraspecific interactions. Sociobiology An international journal on social insects

behavior of Dinoponera species (Planqué et al., 2010;Araujo et al., 2015;Curbani et al., 2021). Few ecological studies are available (see Peixoto et al., 2008Peixoto et al., , 2010, but, as a threatened species, nesting and foraging data are crucial for conservation plans. Herein, we add further information on intraspecific nonagonistic and interspecific agonistic interactions, guarding, and maintenance of the nests, foraging activities and orientation mode performed by D. lucida. We carried out observations from September 29th to October 2nd, 2017, in the Reserva Natural Vale (22.711 ha), municipality of Linhares, northern of Espírito Santo state, southeastern of Brazil. We observed D. lucida workers in foraging activity for 48 hours (cumulative sampling), continuously from 6 AM to 6 PM for four days, from three distinct nests in a 30 m x 30 m plot in a lowland coastal forest (19º 09' 14.5" S, 40º 04' 14.0" W).
The solitary workers of D. lucida foraged for food around the nests, covering an estimated area of 11 m 2 (based on mean radius reached by workers). Workers do not appear to have specific pattern displacement or preference for any area. They randomly forage in their territory making a sinuous route while touching the leaf litter with antennae. We did not observe workers entering in nests other than their own nests, nor aggressive interactions between nestmates. Dinoponera lucida had colony fidelity throughout sampling. Workers returned straight to their original nests after capturing prey. Dinoponera gigantea (Perty, 1833) had similar returning behavior (Fourcassié & Oliveira, 2002). It is likely that D. lucida has returning strategy that uses directional fidelity within a home range, such as a sense of visual orientation.
In our field interventions, we removed the leaf litter excluding chemical tracks and visual cues, as proposed by Fresneau (1985) for Neoponera apicalis (Latreille, 1802). However, this removal did not change the course of D. lucida workers. This may indicate that D. lucida uses fixed visual cues in the environment that go beyond the leaf litter landmarks, such as trunks, branches, roots and shrubs, being important to define its stereotyped routes. In the Dinoponera genus the use of visual cues has already been reported to D. gigantea (Fourcassié et al., 1999) and D. quadriceps (Azevedo et al., 2014). It is known that solitary forager ants learn individual stereotyped routes to increase their navigation efficiency (Wystrach et al., 2011b), to obtain a food source (Fresneau, 1985) or to return to the nest (Wystrach et al., 2011a). Forest ants, as D. lucida workers in foraging activity can have highly stereotyped routes between the nest and the feeding locations (Niven, 2007). This orientation strategy was also reported for D. gigantea (Fourcassié & Oliveira, 2002) and D. quadriceps (Azevedo et al., 2014).
Dinoponera lucida displayed permanent guard and maintenance of their nest. We observed sentinel workers at the nest's openings demonstrating guarding behavior (Fig 1A). Permanent nest guarding and maintenance were previously reported for D. lucida (Peixoto et al., 2010) and D. quadriceps (Medeiros et al., 2016). Probably, guarding activity inhibits non-nestmates intruders to access the nest. In addition, the workers also performed nest opening maintenance, such as removal of leaves, sticks, soil pellets and fallen plant fragments. The maintenance of nests was more evident on the third sampling day, with an increase in the number of workers at nest openings after rain (Fig 1B). This behavior seems to be an immediate response of the workers of D. lucida to the environmental changes that could lead to risk-altering nest's functions.
We observed two non-agonistic interactions between workers from the same nest. In the first interaction, two workers displayed rapid antennation, moving away and continued solitary foraging. In the second interaction, workers cooperated in the transport of a seed to the nest. The first worker carrying a seed (Swartzia myrtifolia var. elegans; Fig  2A), dropped it when founded another worker, and returned to forage. Immediately, the second worker took the seed and returned to the nest (Fig 2B). In addition, we observed that the second worker foraged the leaf litter unlikely to follow a predefined route to find the nestmate. Generally, poneromorph ants do not cooperate during foraging (Fourcassié & Oliveira, 2002;Araújo & Rodrigues, 2006), but cooperation in D. lucida should not be a rare behavior. Labor division, and thus the observed cooperation between workers in the species, seem to follow age polyethism (individual age) (Peixoto et al., 2008).
We observed two agonistic interactions, both between foraging workers from nests 1 and 2 that occurred about 4 m from the openings of their nests (Fig 3). The interactions lasted 1 to 5 minutes. On both occasions, we observed the movements and behavior typical of agonistic interactions described for D. lucida and congeners, such as antennal boxing, gaster bending, bite in the legs and attempts to sting the opponent. At the end of the agonistic interactions, the workers moved away without any apparent damage and returned to forage. Agonistic encounters observed herein for D. lucida were similar to other Dinoponera species (Fourcassié & Oliveira, 2002;Peixoto et al., 2008). Peixoto et al. (2010) observed that the maximum distance reached by D. lucida workers in foraging activity was inversely related to the density of nests in the area, which indicates a strategy to minimize agonistic interactions. We found nests distant from each other at least 8.5 m (the distance between nests 1 and 2) and the mean reached distance by a worker was 3.8 ± 0.4 m (mean ± standard error). The low frequency of agonistic encounters may be due to the fact that workers from different nests usually do not forage in the same area.
Our results expand knowledge about natural history of D. lucida through data on foraging activities, guarding and maintenance of the nests, orientation mode and intraspecific interactions. However, descriptive data on Dinoponera species are still scarce. In addition, we suggest that long-term monitoring is feasible to assess natural history aspects of D. lucida, improving knowledge about the lifestyle of poneromorph ants.