The present study aimed to evaluate the diet of the free-living crab-eating fox by identifying the stomach contents of the 17 crab-eating foxes (Cerdocyon thous) roadkilled in two conservation units, both located in the Amazon rainforest. The food items were quantified by frequency of occurrence (FO) and percentage of occurrence (PO). The stomach contents were analysed for dry matter (DM), crude protein (CP), crude fibre (CF), ether extract (EE), and mineral matter (MM). Nitrogen-free extractives (NFE), metabolisable energy (ME) values, as well as the energy need for maintenance were estimated. The composition of the diet for the crab-eating fox presented 29 food items from the different taxonomic groups, with a greater diversity of items of animal origin (n=22), although the highest frequency of occurrence was gramineae (Poaceae) (41.18%). Among the items of animal origin, 21% were mammals, 18% reptiles, 10% amphibians, 9% invertebrates and 3% birds. A high content of CF (62.76%) were determined. Nitrogen-free extractive and dry matter averages were 5.91% and 141.82 kcal/100g, respectively. The average maintenance energy was 447.01 kcal/day. These findings suggesting that the crab-eating foxes have a generalist diet with an omnivorous diet in the Amazon basin, feeding on gramineae, fruits, insects, snakes, amphibians, birds and small mammals and have the same feeding habit that present in other Brazilian biomes.

Asking how prey respond to different species of predators helps understanding the repertoire of defenses prey exhibit. This approach may also add to the knowledge on the efficiency of prey′s defenses against each predator and allows studying the costs of being attacked by different predators. Here, we studied interactions between the predatory terrestrial flatworm Cephaloflexa bergi and the harvestman Mischonyx cuspidatus. The flatworm quickly strikes at the prey′s leg with its head, then crawls towards the prey′s body releasing mucus and thus subdues the harvestman. Harvestmen may release defensive chemicals and pinch the flatworm with spines on legs IV, sometimes cutting the predator in two pieces. We also experimentally assessed the benefits of harvestmen′ defense and the cost of being attacked by testing whether the chemical defense of the harvestmen is efficient against the flatworm and whether the harvestmen that had survived a flatworm attack would have their locomotion abilities hampered. Both hypotheses were corroborated. Previous studies on interactions between harvestmen and other predators, such as spiders and scorpions, had shown that defensive secretions and mechanical retaliation were seldom used and were often ineffective. Our results point to the exact opposite and suggest that different predators exert different selective pressures culminating in the array of defenses exhibited by the prey.