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Objetivo. Determinar la abundancia relativa y los patrones de actividad de la zarigüeya común (Didelphis marsupialis) en una zona periurbana del municipio de Medellín, departamento de Antioquia. Materiales y métodos. El estudio se desarrolló en la sede de prácticas y clínica veterinaria Remington ubicada en el corregimiento de Santa Elena. Para el registro de datos se empleó la metodología de fototrampeo durante 3 meses (junio-agosto de 2017), invirtiendo un esfuerzo total de 166 días/trampa. Resultados. Se obtuvieron un total de 275 registros independientes de la especie y se estimó una abundancia relativa de 52.88. El patrón de actividad muestra un primer pico de actividad al comienzo de la noche (19:00) y un segundo pico en la madrugada (3:00), con una posterior disminución hacia las horas de la madrugada. Conclusiones. Los resultados muestran una abundancia relativa alta con respecto a otras localidades en Colombia, además de evidenciar una población reproductivamente activa. Al mismo tiempo se convierten en una herramienta para el fortalecimiento de estrategias de conservación y sensibilización a los pobladores locales sobre la fauna de la región.

Fauna in Tropical Dry Forest (TDF) is highly dependent on water availability due to a marked seasonality in precipitation. There are few studies addressing carnivore’s ecology and the role of seasonality of TDF in Neotropics. We used scent-station and camera trapping to assess seasonal changes in occurrence and habitat use probability with seasonality. We also described activity patterns and collected fresh scats to describe diet for small sized carnivore species in a TDF fragment in the Colombian Caribbean region. We present information regarding: Cerdocyon thous, Leopardus pardalis, and Procyon spp. The analysis showed a significantly higher occurrence probability during the dry season for the three species, and no differences in the detection probability between seasons. The diet of C. thous included 24 different food items; for L. pardalis it was composed of seven items, and finally, 25 food items were identified in the diet of Procyon spp. We found that the three species presented activity patterns corresponding with previous studies. Finally, our results reflect that these species are probably making more/larger habitat use during the dry season than in the wet season, because the area has permanent water ponds by which limited resources (such as water and food) are available almost constantly in this natural reserve.

Many animals form aggregations with individuals of the same species (single-species aggregations, SSA). Less frequently, individuals may also aggregate with individuals of other species (mixed-species aggregations, MSA). Although the benefits and costs of SSA have been intensively studied, the same is not true for MSA. Here, we first review the cases of MSA in harvestmen, an arachnid order in which the records of MSA are more frequent than other arthropod orders. We then propose several benefits and costs of MSA in harvestmen, and contrast them with those of SSA. Second, using field-gathered data we describe gregariousness in seven species of Prionostemma harvestmen from Costa Rica. These species form MSA, but individuals are also found solitarily or in SSA. We tested one possible benefit and one possible cost of gregariousness in Prionostemma harvestmen. Regarding the benefit, we hypothesized that individuals missing legs would be more exposed to predation than eight-legged individuals and thus they should be found preferentially in aggregations, where they would be more protected from predators. Our data, however, do not support this hypothesis. Regarding the cost, we hypothesized that gregariousness increases the chances of parasitism. We found no support for this hypothesis either because both mite prevalence and infestation intensity did not differ between solitary or aggregated individuals. Additionally, the type of aggregation (SSA or MSA) was not associated with the benefit or the cost we explored. This lack of effect may be explained by the fluid membership of the aggregations, as we found high turnover over time in the number of individuals and species composition of the aggregations. In conclusion, we hope our review and empirical data stimulate further studies on MSA, which remains one of the most elusive forms of group living in animals.