Animals are under constant pressure to survive in their surrounding environment, and they have evolved countless strategies to adapt, colonize, and reproduce successfully in their habitats.1 Almost acting as materials scientists, animals may directly manipulate complex fluids around them or secrete complex fluids themselves to fulfill a specific task. Mucus, for example, demonstrates a wide range of rheological properties depending on its physiological purpose—locomotion, sexual reproduction, protection against predators, or one of countless other uses. And when conditioned properly, sand present in the habitat can be used for movement or for predation.

Rheologically active materials—those with unusual or nonlinear responses to an applied force (stress) or deformation (strain)—often have clearly defined action windows, so matching the material properties with an animal’s desired outcome is essential. To exploit the rheological properties for the specific task, the animal therefore must sense and, if needed, manipulate the rheology of the surrounding complex...

You do not currently have access to this content.