Molecular methods are increasingly used to identify prey DNA in predators' faeces to describe diet composition. However, such analysis can reveal much more ecological information. If faeces are regarded as ‘biodiversity capsules’, they can help describe and quantify ecological communities by containing a representative sample of the prey species occurring in the foraging area of a given predator. Here we propose to analyse these ‘capsules’ and infer the occurrence, distribution and minimum abundance estimate of prey communities. This novel approach goes beyond the detection of ‘targeted’ prey groups to inform dietary studies of predators. It is particularly suited to the study of prey communities that are difficult to sample with traditional methods because they are very small, rare and/or live in remote or inaccessible habitats. Such communities include invertebrates inhabiting the soil, deep-sea species, and small, rare flying insects. The proposed approach has the potential to inform the topical issue of biodiversity assessment and provide a new framework for the discovery of species with minimum interference to ecosystems and without the need for extensive trapping, which can be labour intensive and could kill many individuals of non-target species. Rigorous testing of this approach, and in particular direct comparison with traditional sampling methods is required to fully demonstrate its efficacy.