Cannibalism is widespread across the animal kingdom, occurring in more than 1300 species of invertebrates and vertebrates across terrestrial and aquatic habitats (Fox, 1975; Polis, 1981; Elgar and Crespi, 1992). Cannibalism, defined as the consumption of all or part of a conspecific individual, can occur during multiple stages in the life cycle of an organism (Elgar and Crespi, 1992).  As such, cannibalism potentially affects animal behavior, life history strategies, population size and reproductive success (Cushing et al., 2015). Intra- and inter-specific competition, overcrowding, lack of food, or poor quality food are all stressors that induce cannibalistic behavior (Elgar et al., 1992). Cannibalistic individuals should even be selected for since those individuals would gain nutritional resources with high stoichiometric compatibility and face decreased intraspecific competition (MacArthur et al., 1966; Mitra & Flynn, 2005). Acquisition of high quality nutrients and reduced competition lead to increased growth efficiency and survivorship (Mitra & Flynn, 2005), so cannibals are more likely to survive high conspecific recruitment years and low prey recruitment years. As a result, cannibalistic individuals are more likely to successfully reproduce and spread cannibalistic tendencies throughout their population, a strategy that has recently been shown to be evolutionarily stable (Cushing et al., 2015). While cannibalism is therefore both predicted and observed to be widespread in nature, we have recently observed cannibalism in an unexpected setting: among newly metamorphosed juvenile sea stars (Figure 1; VideoS1). Cannibalism among juveniles has been reported in Arachnids, Insects, Amphibians and Reptiles (reviewed by Elgar and Crispi, 1992), but has only rarely been reported or described in marine invertebrates (but see Byrne, 1996).