Definitions for "Umwelt"
Sensory World. Subjective set of stimuli to which an animal is responsive in a given motivational state. Each species has evolved responses only to those stimuli that prove relevant. It is this simpler world that actually falls within the animal's perception at any particular moment.
a 'lived world', where the things we observe take on significance
The sensory and perceptual world of the animal, dependent upon the types of sensory receptors that it possesses and the internal nervous system processes for receiving and interpreting those stimuli.