Aquatic Foraging in Snakes: From Morphology to Behavior

Despite their lack of limbs, snakes have successfully invaded all possible habitats. From burrowing to gliding or swimming, without mentioning moving in or above sand, snakes have developed specific adaptations to deal with the physical properties in all these different environments. Aquatically foraging snakes are particularly interesting, with more than 300 species invading water at various degrees; from species that never leave water, to species that are mostly terrestrial yet occasionally feed on fish. Snakes are primarily adapted to terrestrial conditions; thus to detect and capture a prey S57 living in a dense and viscous fluid (such as water) has required additional adaptations. Underwater prey capture results in strong hydrodynamic constraints on the head of snakes, so they have converged toward a head shape that reduces these hydrodynamic
forces. Some snakes use different behavioral strategies to capture their prey, to also circumvent hydrodynamic constraints. But before catching its prey, the predator must detect it, and the physical properties of water also affect the propagation of sensory cues in comparison with air. Moreover, other characteristics of water can also disrupt the propagation of some signals, such as turbidity and flow. How has the sensory system of snakes adapted to detect prey under water? Are these sensory abilities related to the shape of the brain? What is the relationship between brain, braincase and head shape in snakes? These are all questions we are currently addressing
comparing the brain and braincase of several species of snakes using μCT-imaging of both iodine stained and unstained collection specimens. The sensory modalities are assessed by using behavioral experiments to isolate each sense and measure the response of the animal to a stimulus. Using this combined approach, we are able to
draw the link between the properties of the environment, the sensory modalities, and the morphology of the head, brain and braincase of aquatic snakes.