This is just an RNG nightmare.
I got an uncommon baby ape my first day there, had no idea they were hard to get..just got him while gathering up other pets never even knew it was a rain only pet (not caring about quality at all).
Now that I am getting around to upgrading everything to rares, I have alts parked on that island on 2 US servers, a Latin american server and the Brazil server. I haven´t even seen it rain, let alone get a rare.
I wish they would have set it up to where the really annoying wild pets to capture were not beasts or flying.. lol.. since I don´t have stones available. At least with the Vukry and minfernal, it was a no brainer to use a stone.