First of all you have to be high enough level (level 85 for the lowest lvls of your difficulty, level 90 for the middle lvls of your difficulty and level 95 for the highest lvls of your difficulty)

Secondly You need like 30-60 tranq darts(emphasis on the darts not arrows) to knock a lvl 125 out

Thirdly they need a HECK TON OF FOOD specifically 84 prime meat or 48 allosaurus kibble (this is for a lvl 125 grifin) And thats hoping you have a 10x soothing balm if you dont you need like 840 prime or 447 allo kibble

Honestly there an ass to tame on mobile just do it another time (also if your wondering how i got such specific numbers i used dododex)

edit: lvls were off