The effects of introducing the Amazonian squirrel monkey on the behavior of the northeast marmoset / Efeitos da introdução do macaco-de-cheiro amazônico sobre o comportamento do sagui-do-nordeste

The squirrel monkey Saimiri sciureus, an endemic primate of the Amazonian Basin, has been introduced in many localities of the Atlantic Forest biome. Introduced exotic species gain a competitive advantage in their new environment because of a lack of natural predators, competitors or diseases. This advantage can result in a reduction in the resources for the endemic species. The aims of this work were to evaluate the level of adaptation, and monitor the forms of interaction and the impact caused by S. sciureus on the behavior of the native species Callithrix jacchus in the Saltinho Biological Reserve, Tamandaré, Pernambuco, Brazil. The behavior was assessed by use of scan sampling method, every 5 min. A total of 382 h (191 h or 2,292 scans per group) of time sampling was performed. Sixteen interactions were recorded. The interaction index was low and represented 2.4% of the total observation time. Interactions were significantly higher during the dry season (58.5%) relative to the rainy season (41.5%). Callithrix jacchus was intolerant to the presence of S. sciureus and the last one was more tolerant during the interactions. In the presence of S. sciureus, C. jacchus eating, foraging, resting, socializing, and self-grooming behaviors were reduced while alertness was increased. Territorial behavior showed no significant difference. In the presence of S. sciureus, on average, the group of marmosets assembled at a higher layer of the forest stratum. The results might indicate a negative effect of S. sciureus on the native species, C. jacchus.

O mico-de-cheiro, Saimiri sciureus, uma espécie endêmica da Bacia Amazônica, tem sido introduzido com sucesso em muitas localidades do bioma Mata Atlântica. Espécies exóticas introduzidas adquirem uma vantagem competitiva em seu novo ambiente por causa da ausência de seus predadores naturais, resultando em uma redução dos recursos alimentares para as espécies endêmicas. Nossos objetivos foram avaliar o nível de adaptação e monitorar as formas de interação e do impacto causado pelo S. sciureus sobre o comportamento da espécie nativa, Callithrix jacchus, na Reserva Biológica de Saltinho, Tamandaré, Pernambuco, Brasil. O comportamento foi estudado através do método de amotragem scan sampling a cada 5 minutos. Um esforço amostral de 382 h (191 h ou 2.292 scans por grupo) foi obtido. Dezesseis interações foram registradas. O índice de interação foi baixo e representou 2,4% to total de tempo de observação. As interações foram significantemente maiores na estação seca (58,5%) do que na estação chuvosa (41,5%). Em termos de tipos de interação, C. jacchus foi intolerante à presença de S. sciureus, que por sua vez apresentou alto nível de tolerância. Na presença de S. sciureus, o C. jacchus reduziu a alimentação, forrageamento, descanso, comportamentos sociais e autocatação e aumentou o comportamento de alerta. O comportamento territorial não apresentou diferença significante. Na presença do S. sciureus, no geral, o grupo de saguis permaneceu em um estrato mais alto na floresta. Os resultados parecem indicar um possível efeito negativo do S. sciureus sobre a espécie nativa, C. jacchus.

Do omnivorous shrimp influence mayfly nymph life history traits in a tropical island stream?

Interspecific interactions can play an important role in determining habitat selection and resource use between competing species. We examined interactions between an omnivorous shrimp and a grazing mayfly, two co-dominant taxa found in Puerto Rican headwater streams, to assess how predator presence may influence mayfly resource use and instantaneous growth in a tropical rainforest ecosystem. We conducted a series of behavioral and growth experiments to determine the effects of the freshwater shrimp, Xiphocaris elongata, on the growth rate and resource selection of mayfly nymphs in the family Leptophlebiidae. For resource choice assessments, we conducted a series of five day laboratory experiments where mayflies were given access to two resource substrate choices (cobble vs. leaves) in the presence or absence of shrimp. To assess for the effects of shrimp on mayfly fitness, we measured mayfly growth in laboratory aquaria after five days using four treatments (cobble, leaves, cobble + leaves, no resource) in the presence or absence of shrimp. In resource choice experiments, mayflies showed preference for cobble over leaf substrata (p<0.05) regardless of the presence of shrimps, however, the preference for cobble was significantly greater when shrimp were present in the leaf habitat. In growth experiments, there were no statistical differences in mayfly growth in the presence or absence of shrimp (p=0.07). However, we measured increased mayfly nymph growth in the absence of predators and when both cobble and leaves were available. Our results suggest that interspecific interactions between these taxa could potentially influence organic matter resource dynamics (e.g., leaf litter processing and export) in Puerto Rican streams. Rev. Biol. Trop. 62 (Suppl. 2): 41-51. Epub 2014 April 01.

Las relaciones interespecíficas pueden jugar un papel importante en la determinación del uso de recursos y selección de hábitat entre especies que compiten. Hemos examinado las interacciones entre un camarón omnívoro y un efemeróptero que se alimenta de vegetación , dos taxones codominantes en las partes altas de arroyos de Puerto Rico, para evaluar el efecto de los depredadores en el uso de recursos del efemeróptero y el crecimiento instantáneo en un ecosistema de selva tropical. Examinamos experimentalmente el efecto del camarón Xiphocaris elongata sobre la tasa de crecimiento y selección de recursos en ninfas efemerópteras (Leptophlebiidae). Hicimos experimentos de laboratorio de 5 días, dando a los efemerópteros acceso a dos opciones de sustrato (piedrecillas u hojas) en presencia o ausencia del camarón. Para evaluar los efectos sobre el crecimiento probamos cuatro tratamientos (piedrecillas, hojas , piedrecillas + hojas, sin ambas), en presencia o ausencia del camarón. Los efemerópteros prefirieron las piedrecillas a las hojas ( p < 0,05 ) independientemente de la presencia de los camarones. Esta preferencia fue mayor cuando junto a las hojas había camarones. Los camarones no afectaron el crecimiento de los efemerópteros (p = 0,07). Las ninfas efemerópteras crecieron mejor sin camarones y en acuarios con piedrecillas y hojas. Nuestros resultados sugieren que las interacciones interespecíficas entre estos animales podrían influir en la dinámica de la materia orgánica (por ejemplo, procesamiento de la hojarasca y su exportación) en los arroyos puertoriqueños.