Don't bola them. Climb a huge rock and use a decent slingshot on their head. Kill the ones you don't want with arrows and bring about 40 berries, they torpor is trash so if you don't have enough just harvest bushes nearby, they are mainly found at beaches.

They saddle is fairly expensive but this turtle is overall a good water mount for begginers. Don't use it for multi player fights though, they're painfully easy to kill.