Warrant leads an active research group studying vision and visual navigation in animals from extremely dim habitats (nocturnal and deep sea). Using electrophysiological, optical, histological, behavioral and theoretical approaches, Warrant studies how animals as diverse as nocturnal insects, deep-sea cephalopods and fast-swimming predatory fishes are able to see well at very low light levels, and his research has led to the discovery of neural principles that permit vision in dim light.