The first pet, the cat is a normal pet, that can be found in the north of winterspring, lvl is around 57 to 60.
The rest are rare elites, that spawn at different spots and times. So if killed or tamed, they mostly don't come back for a couple of hours. So either you camp the spawn points for endless hours or you just have to be very lucky.
For the below mentioned rare's you need to have the 51 point from Beast Mastery (the one for exotic pets) to be able to tame them.
Loque'nahak is a rare lvl76 found in Sholazar Basin.
Gondria is a rare lvl 77 found in Zul'Drak
Arcturis is a rare lvl 74 found in Grizzly Hills
I don't like Skoll personaly, but here is a pic, he is also a rare elite, lvl 80 and is found in The Storm Peaks.