Size-based niche partitioning permits coexistence in natural populations of <i>Nicrophorus</i> spp.

When species compete over similar resources, niche partitioning can permit ecologically similar species to coexist. Such coexistence should be a particular challenge for carrion-feeding invertebrates, with the ephemeral nature of carrion leading to intense competition over this nutrient-rich resource. Here we tested whether the carrion niche in four species of coexisting burying beetles (Nicrophorus spp.) is partitioned seasonally or by species size in seven ancient woodlands in the United Kingdom. We fail to replicate the results of previous studies in the UK that found a strict seasonal separation in the activity of competing burying beetle species. Instead, our data support the hypothesis that the niche is partitioned by species size. We present field evidence consistent with the hypothesis that smaller species are less successful at contested carcasses and confirm that sexual dimorphism in head width, a trait likely related to competitive ability, is present in several species of Nicrophorus. We discuss the considerable but as-of-yet unnoticed variation between different geographic populations of Nicrophorus spp. in how the carrion niche is partitioned.