Effects of intraspecific competition and body mass on diet specialisation in a mammalian scavenger

1. Animals that rely extensively on scavenging rather than hunting must
exploit resources that are inherently patchy, dangerous, or subject to
competition. Though it may be expected that scavenging species should
therefore form opportunistic feeding habits in order to survive, a broad
population diet may mask specialisation occurring at an individual level.
2. To test this, we used stable isotope analysis to analyse the degree of
specialisation in the diet of the Tasmanian devil, one of few mammalian
species to develop adaptations for scavenging. 3. We found that the
majority of individuals were dietary specialists, indicating that they fed
within a narrow trophic niche despite their varied diet as a population.
4. Even in competitive populations, only small individuals could be
classified as true trophic generalists; larger animals in those
populations were trophic specialists. In populations with reduced levels
of competition, all individuals were capable of being trophic specialists.
5. Heavier individuals showed a greater degree of trophic specialisation,
suggesting either that mass is an important driver of diet choice or that
trophic specialisation is an efficient foraging strategy allowing greater
mass gain. 6. Devils may be unique among scavenging mammals in the extent
to which they can specialise their diets, having been released from the
competitive pressure of larger carnivores.