Animal Birth Control is needed especially in a city like Mumbai. Stray cats and dogs that are not sterilized give birth to kittens and puppies which have a minimalistic rate of survival. From the very few kittens and puppies that actually make it, very few are well fed and well taken care of. Most of them die due to illnesses, starvation, road accidents amongst other reasons. Thus, the need to sterilize them is vital.
Also, the cats and dogs that are sterilized usually live a longer life, have lower risks of cancer, have better behavioural patterns and most importantly lower overpopulation.
Vaccination also ensures the prevention of many diseases such as rabies, distemper to name a few.