Predation of the slender opossum Marmosops caucae (Didelphimorphia, Didelphidae) on the venomous spider Phoneutria fera (Araneae: Ctenidae) in Amazonian Ecuador, with a dietary overview for the genus Marmosops

Small marsupials of the genus Marmosops are widely regarded as omnivore-insectivores, but quantitative information on their diets is fragmentary. Here, we report the first verified predation event of the highly venomous wandering spider Phoneutria fera by Marmosops caucae during a nocturnal survey in Amazonian Ecuador, and provide the most comprehensive synthesis to date of prey use within the genus, based on a literature review and participatory science observations. The synthesis yielded nine primary studies and three iNaturalist records offering diet data for six Marmosops species. Collectively, these records encompass 15 invertebrate orders and five vertebrate classes; Coleoptera and Hymenoptera dominate, whereas large arachnids occur only sporadically. The breadth and composition of prey spectra are best explained by local availability rather than dietary specialisation, underscoring the genus's behavioural flexibility. Our observation expands the known trophic interactions of Marmosops and highlights the need for experimental work on venom tolerance and potential ecological effects on spider guilds.