Sterilize

hello guys,

I've seek advise from heartkiel on tis issue and her advise is it's better to sterilize the cat.

Normally,how do they indicate whether the cat have been sterilize?I've notice that most of the stray cats have their ear tip cut off after they are being sterilize.

I'm afraid if I send my scott for sterilize,they will do the same too.Already the scott ear is short if they cut the tip off he will look like alien.
Any other ways beside cutting the ear?