What is the surgical procedure for the removal of testicles or ovaries called?

The surgical procedure for the removal of testicles or ovaries is known as orchiectomy (for the removal of testicles) and ovariectomy (for the removal of ovaries). The term "neuter" is generally used as an umbrella term to refer to the surgical sterilization of an animal, which includes both orchiectomy and ovariectomy, but does not specifically indicate which procedure is being performed.

Orchiectomy specifically describes the surgical removal of the testicles in male animals, which is a standard procedure for controlling reproduction and certain behavioral issues. The use of the term in the context of testicle removal makes it the correct answer, as it precisely defines the surgical action taken.

The other choices relate to different procedures: declaw refers to the surgical amputation of a cat's claws, and euthanasia refers to the humane killing of an animal to relieve suffering. Neither of these involves the removal of testicles or ovaries. Therefore, focusing on the precise definitions and functions of the listed medical terms highlights why orchiectomy is the correct answer for the question.