Feeding mechanisms in bats: variation within the constraints of flight.

By any standard, bats are a successful group of mammals and the evolution of flight and echolocation were certainly key innovations behind their success. That is only part of the story, however. Bats have diversified into trophic niches that range from insectivory to feeding on blood, fruit, or nectar. While flight places fundamental constraints on the shape of the postcranial skeleton, skull shape in bats is remarkably diverse. Morphological studies of individual families and sympatric assemblages demonstrate that variation in skull shape is clearly associated with trophic specialization. Field experiments demonstrate that species-specific biting behaviors during feeding are common and analyses indicate that the evolution of cranial morphology and feeding behavior are correlated. Modeling experiments further suggest that feeding (loading) behaviors and skull shape are functionally linked. If the skulls of bats are under selective pressure for minimal mass because of the energetic demands of flight, then they may be more "optimized" to meet mechanical demands than are the skulls of other mammals. This would make bats a unique model system for studying the evolution of diversity in skull shape and its functional implications for the evolution of feeding strategies in mammals.