Investigation of vertebrate regulatory biology is restricted by the modest response amplitudes in mammalian model species that derive from a lifestyle of frequent small meals. By contrast, ambush-hunting snakes eat huge meals after long intervals. In juvenile pythons during feeding, there are large and rapid increases in metabolism and secretion, in the activation of enzymes and transporter proteins, and in tissue growth. These responses enable an economic hypothesis concerning the evolution of regulation to be tested. Combined with other experimental advantages, these features recommend juvenile pythons as the equivalent of a squid axon in vertebrate regulatory biology.