Camouflage is often thought of as a way to conceal appearances, implying due attention be paid to the sense of vision and how to deceive it. Pertinent to this notion is to remember that adequate camouflage also includes addressing the aural ambience of an environment as well as smells and textures in order to mimic each element in deceiving an enemy.
Shinobi were well acquainted with the visual aspect of camouflage.
They possessed the ability to assume a number of credible disguises and concealed a great variety of weapons with ingenuity (hidden swords, fukiya that doubled as flutes, etc.). But an often overlooked aspect of ninjutsu is the accentuated attention that the shinobi paid to the environment and how to read the calls and behavior of the animals and insects in an area. For example, birds taking flight or going silent in a forest conveyed the presence of a disturbance; game-trails could lead to water; and the oral mimicry of fauna offered a way to communicate without arousing suspicion.
The shinobi agent is known to have mimicked the cries and sounds of a cat for the purpose of concealing an entrance into a dwelling.
Just how an agent trained this technique is difficult to say. Though animal mimicry is an obscure skill, in expert hands it may have been quite useful.