The rainy season paid no attention to the calendar and the downpours continued.    The water was high at the Madre Selva field station, high enough to reach the steps of the kitchen tambo, and to leave the station’s generator on its own island.   The boats were tied up close to the kitchen, and one night, Dan Wylie spotted something sculling along the bottom next to the skiff.  “Pipa!” he shouted, but he could not get hands on it before it scooted away into deeper water. A few nights later, we were paddling down the Rio Orosa, coming back after a night of chasing black caiman back in the varzea, and I spotted my first Pipa pipa as it swam under…