You are wrong. Please look it up yourself....According to evolutionists, MUTATIONS ARE NOT based on the needs of the animal. These mutations are spontaneous and RANDOM. Most of these mutations take form of ACCIDENTAL copying errors. These errors are supposedly then "SELECTED."....which simply means "decided on" by natural selection (ie the environment, needs etc)
The whole theory of evolution is based on accidents, driven by selection. If someone were to prove that an animal evolved certain characteristics as a direct result of it's environment, then Darwin's theory would be falsified. Instead, they say that traits form by accident, and then "natural selection" determines if the traits should stay amongst the population.