Flexibility in the integration of environmental information by Dinoponera quadriceps Kempf during foraging

Abstract Foraging behavior requires animals' behavioral flexibility to exhibit efficient strategies that result in the successful search for food. The navigation of ants enables long distance trips back and forth from the nest, using orientation cues. We analyzed the flexibility of Dinoponera quadriceps workers in integrating information introduced into the environment. We studied workers from two colonies in an area of secondary Atlantic Forest, with the use of a physical obstacle placed in front of the entrance of the nest with no fixed angular position. There was no significant difference in the resolution time workers to bypass the obstacle, in the angles between trips when exiting and returning to the nest, or in the positioning angles when returning to the nest. However, we found an increase in positioning angles when leaving the nest to search food, from the second contact onwards. They overcame the new obstacle as they would any other natural one. The presence of the obstacle did not prevent workers from maintaining route fidelity to individual areas. The behavior of D. quadriceps workers indicates that they have the flexibility to incorporate new information in a familiar environment. They likely use multimodal cues, which prevent them from wandering outside the familiar area.

Seasonal activity of Dinoponera quadriceps Santschi (Formicidae, Ponerinae) in the semi-arid Caatinga of northeastern Brazil

Seasonal activity of Dinoponera quadriceps Santschi (Formicidae, Ponerinae) in the semi-arid Caatinga of northeastern Brazil. We studied seasonal foraging patterns of the queenless ant D. quadriceps (Formicidae, Ponerinae) for 24 months in a Caatinga area of northeastern Brazil, an ecosystem characterized by strong climatic changes throughout the year, in order to determine if regulation of worker activity is based on environmental conditions (air temperature, relative humidity, precipitation) and/or food resources (potential prey: Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Orthoptera, Araneae, Chilopoda and Diplopoda). Foraging activity of D. quadriceps varied over the course of both years, with the highest frequency occurring from May to August, corresponding to the late rainy season and early dry season. This foraging activity was negatively correlated with temperature and positively correlated with the availability of potential prey, but not with total abundance of soil arthropods or with rainfall and relative humidity. Diet composition, in relation to the main taxonomic prey groups, seems to be common to the species, regardless of habitat. Our results suggest that D. quadriceps workers adjust foraging activity to the most suitable period of the year, to avoid thermal stress and increase efficiency. Thus, they present an appropriate behavioral response to seasonal fluctuations in the Caatinga.

Atividade sazonal de Dinoponera quadriceps Santschi (Formicidae, Ponerinae) em caatinga semiárida do nordeste brasileiro. Foi estudado o padrão de forrageamento da formiga sem rainha D. quadriceps (Formicidae, Ponerinae) durante 24 meses em uma área de caatinga do nordeste brasileiro, um ecossistema caracterizado pelas fortes mudanças climáticas ao longo do ano, com objetivo de determinar se a atividade das operárias é regulada pelas condições ambientais (temperatura do ar, umidade relativa, precipitação) e/ou recursos alimentares (presas potenciais: Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Orthoptera, Araneae, Chilopoda e Diplopoda). A atividade de forrageamento de D. quadriceps variou ao longo dos dois anos, com a maior freqüência ocorrendo de maio a agosto, correspondendo ao final da estação chuvosa e início da estação seca. Essa atividade de forrageamento foi negativamente relacionada com a temperatura e positivamente relacionada com a disponibilidade de presas potenciais. Não houve relação com a abundância total de artrópodes de solo, precipitação e umidade relativa. A composição da dieta, em relação aos grupos taxonômicos das presas, parece ser comum à espécie, independente do habitat. Os resultados sugerem que as operárias de D. quadriceps ajustam sua atividade de forrageamento ao longo do ano para evitar estresse térmico e aumentar sua eficiência. Desta forma, elas possuem uma resposta comportamental apropriada para a flutuação sazonal da Caatinga.