What was the first thing Uri ate on the new island in Chapter 3 of Call It Courage?

So far as we know, the very first thing that Uri eats when
he and Mafatu get to the island is a robber crab.  We cannot be absolutely sure,
however, that this is the first thing he eats.

At the
beginning of Chapter 3, Mafatu is just regaining consciousness after making it to the
island.  He sits up, and he sees Uri holding the crab in his paws, cracking its shell,
and eating it.  We cannot know for certain that this is the first thing he has eaten. 
For all we know, he could have been eating the whole time Mafatu was
unconscious.

As far as we know, though, the robber crab is
the first thing Uri eats on the island in Chapter 3.