Many if not all ground mounts don't protect you from being robbed, so while I used to argue that a fast raptor is as good as a bird you'll have an empty inventory when you get there soooo I guess the fun's over
Pegos are pretty cute. It’s kind of funny to see them running off with a little sack of stuff. That is, until that sack contains your entire supply of narcotics. (How did he not die that had like fifty narcotics that’s like chugging two hundred bottles of Nyquil HOW)
I found one while I was taming a Lystrosaurus. I was feeding it and the Pegomastax took it and it was tamed... Completely by accident. Course another one showed up, so I threw a grenade and it killed them both. Oops
Have a Dimorphodon follow you (not on your shoulder) with extra points on speed, he will go after the Pego and kill him as soon as he steals from you. Make sure the Dimo can pickup items from corpses so he can get your stuff back.
I always keep my stacks of narcotics and other precious stuff completely split. It May make a mess in my inventory, but when those little bastards and their winged culprits be thievin', I'm like "what ever"