Go for an... arm...? But aiming for something's arm wouldn't kill it. A four legged beast could always make do on three legs. In fact, some once four legged animals had even managed to adapt to using two legs after the loss of other limbs. So... Why was the little mechanical bird thing telling him to aim for a leg? While utterly confused about why he would do it, the Kirund did listen. His maw dug down in to the mud, snapping around to burrow down toward the arm of the Hydrolisk. Finally closer enough, he lunged forward slightly and snapped his jaws tightly.
With any luck(good for the Kirund, bad for the Hydrolisk), he'd get a good enough grip on the arm that either Nandi would be released or he could just rip the darn thing off. If the Hydrolisk turned to attack him, Runt would be more than happy to just rip his arm off to get away without being torn in to himself. Sure he couldn't feel pain all that well, but it was still instinct. If his fangs did manage to connect with the arm, he certainly wouldn't be letting go until he saw the Kuni safe no matter what harm came to him or the aquatic beast.
(Such a sucky post. xD; Anyways, basically he's gonna try to latch on to the Hydrolisk's arm. And will refuse to let go if he does manage to snag it.)