Competition through ritualized aggressive interactions between sympatric colonies in solitary foraging neotropical ants.

Understanding the structure of food competition between conspecifics in their natural settings is paramount to addressing more complex questions in ecology, evolution, and conservation. While much research on ants focuses on aggressive food competition between large and foraging trail-using societies, we lack a thorough understanding of inter-colony competition in socially less derived, solitarily foraging species. To fill this gap, we explored the activity of ten neighbouring colonies of the giant ant Dinoponera quadriceps, monitoring 2513 foraging trips of hundreds of workers and all its inter-individual interactions. We found that, on encountering, workers from different colonies rarely engaged in aggressive fights but instead avoided each other or performed ritualised agonistic bouts. We discovered that during foraging trips, a few workers within each colony repeatedly rubbed their gaster on the substrate, a behaviour not observed in the field before. We propose that workers use this behaviour to mark the foraging area and mark more frequently in its periphery. Only 25% of the individuals specialised in this behaviour, and we hypothesise that the specialisation results from the history of interactions and experience of individual foragers. Our study suggests that workers of contiguous D. quadriceps colonies engage in low-risk conflict, mainly displaying ritualised behaviours. As these small societies mainly rely on tiny, unpredictably scattered, albeit abundant in the environment, arthropod prey, and not on persistent food sources, they do not aggressively defend exclusive foraging territories. On the other hand, colonies rely on large overlapping foraging areas to sustain their survival and growth, most often tolerating foragers from nearby colonies. We discuss whether this type of competitive interaction is expected in all solitary foraging species.

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.

Behavioral responses of freshwater prawn according to feeding management in mixed and monosex populations / Respostas comportamentais do camarão de água doce de acordo com o manejo alimentar em populações mistas e monossexo

The effects of two feeding management methods (substrate spreading and feeding tray) were tested for Macrobrachium rosenbergii, evaluating their influence on behavior in mixed (Mi), monosex all-male (Mm) and monosex all-female (Mf) populations. Twelve experimental conditions, totaling 192 animals, with four repetitions each, were performed. Experimental units comprised eight 250-L aquariums (50 x 50 x 100 cm) with soft sand substrate. Behavioral data were collected by focal instantaneous sampling method. Substrate spreading triggered the most extensive behavioral level in all populations under analysis, featuring exploring, autogrooming, crawling, inactivity, burrowing, agonism, swimming and feed ingestion, and revealed that the animals expressed better their behavior when feed was spread. Exceptionally, burrowing in Mm and agonism in Mf had similar level rates for the two feeding managements. Mf had the highest agonistic level when compared to that in Mm and Mi. Data in current analysis indicate that the spread feeding strategy favors animal welfare in all types of population compositions, except in Mf culture, with high agonistic levels in both forms of feeding management.(AU)

Foram avaliados os efeitos de dois métodos de alimentação (a lanço e em comedouros) e sua influência no comportamento de populações mistas (Mi), monossexo fêmea (Mf) e monossexo macho (Mm) de Macrobrachium rosenbergii, nas fases clara e escura do dia. Foram analisadas 12 condições experimentais, com quarto repetições cada, totalizando 192 animais observados. As unidades experimentais consistiram em 8 aquarios (250 L; 50 x 50 x 100 cm) com substrato de areia fina. Dados comportamentais foram coletados usando método de amostragem focal instantâneo. A oferta a lanço, em todas as composições populacionais, induziu a maiores níveis dos comportamentos de exploração, limpeza, enterramento, inatividade, entocamento, agonismo, natação e ingestão do alimento, indicando que os animais encontraram mais oportunidades para expressão de seus comportamentos com o espalhamento da ração. Como exceção, o comportamento de entocamento em Mm e agonismo em Mf foram semelhantes para ambos tipos de manejo alimentar. O cultivo Mf apresentou maiores níveis de agonismo que Mm e Mi. Nesse estudo, os resultados indicam que, em todos os tipos de composição populacional, a alimentação a lanço favoreceu o bem-estar estar animal, exceto para o cultivo Mf, o qual apresentou altos níveis de agonismo em ambas as formas da estratégia alimentar. (AU)

Behavioral responses of freshwater prawn according to feeding management in mixed and monosex populations / Respostas comportamentais do camarão de água doce de acordo com o manejo alimentar em populações mistas e monossexo

The effects of two feeding management methods (substrate spreading and feeding tray) were tested for Macrobrachium rosenbergii, evaluating their influence on behavior in mixed (Mi), monosex all-male (Mm) and monosex all-female (Mf) populations. Twelve experimental conditions, totaling 192 animals, with four repetitions each, were performed. Experimental units comprised eight 250-L aquariums (50 x 50 x 100 cm) with soft sand substrate. Behavioral data were collected by focal instantaneous sampling method. Substrate spreading triggered the most extensive behavioral level in all populations under analysis, featuring exploring, autogrooming, crawling, inactivity, burrowing, agonism, swimming and feed ingestion, and revealed that the animals expressed better their behavior when feed was spread. Exceptionally, burrowing in Mm and agonism in Mf had similar level rates for the two feeding managements. Mf had the highest agonistic level when compared to that in Mm and Mi. Data in current analysis indicate that the spread feeding strategy favors animal welfare in all types of population compositions, except in Mf culture, with high agonistic levels in both forms of feeding management.

Foram avaliados os efeitos de dois métodos de alimentação (a lanço e em comedouros) e sua influência no comportamento de populações mistas (Mi), monossexo fêmea (Mf) e monossexo macho (Mm) de Macrobrachium rosenbergii, nas fases clara e escura do dia. Foram analisadas 12 condições experimentais, com quarto repetições cada, totalizando 192 animais observados. As unidades experimentais consistiram em 8 aquarios (250 L; 50 x 50 x 100 cm) com substrato de areia fina. Dados comportamentais foram coletados usando método de amostragem focal instantâneo. A oferta a lanço, em todas as composições populacionais, induziu a maiores níveis dos comportamentos de exploração, limpeza, enterramento, inatividade, entocamento, agonismo, natação e ingestão do alimento, indicando que os animais encontraram mais oportunidades para expressão de seus comportamentos com o espalhamento da ração. Como exceção, o comportamento de entocamento em Mm e agonismo em Mf foram semelhantes para ambos tipos de manejo alimentar. O cultivo Mf apresentou maiores níveis de agonismo que Mm e Mi. Nesse estudo, os resultados indicam que, em todos os tipos de composição populacional, a alimentação a lanço favoreceu o bem-estar estar animal, exceto para o cultivo Mf, o qual apresentou altos níveis de agonismo em ambas as formas da estratégia alimentar.