Ecological and evolutionary significance of bark feeding: implications for mammal and plant

1. Mammalian herbivores, when their main food source is limiting can feed on tree bark as a fallback resource. This provides them with a valuable nutritional refuge and exerts critical pressure on plants. Despite its ecological significance, the drivers and adaptations underlying bark feeding remain poorly understood. 2. We synthesise current ecological knowledge on mammalian debarking for both mammals and plants and question what could have been their long-term consequences over vegetations. We compiled a global inventory of bark-feeding mammal species and analysed ecological patterns across orders, body sizes, dietary guilds, biogeographic distributions, and biomes. 3. Nearly half of the 215 mammalian species recorded as bark-feeding are large herbivores (>5 kg), representing up to 20% of large mammals and 21% of woody plant feeders in those clades. Both bark-feeding species richness and relative prevalence are highest in seasonal ecosystems—especially woodlands/shrublands, subtropical deserts, and tropical seasonal forests/savannas. Though representing a minor part of the total diet of most Mammal species, bark is more extensively consumed at times when food is critically scarce, acting as a fallback resource. Some evidence links bark consumption to improved mammalian physiological conditions. For plants, bark feeding can cause tree mortality influencing species diversity, vegetation dynamics, and ultimately ecosystem composition. It was likely more widespread ecological function in megafauna-rich ecosystems and is now greatly reduced. 4. Synthesis. Bark feeding, while corresponding to low amount of biomass being removed, have a disproportionate effect over plant and herbivores fitness, with potential important cascading consequences over vegetation and faunal assemblages.