Only God Hears the Animals

Quite a while ago a young biologist named John Walsh was on a National Geographic mission to the Amazon for the study of some rare animals. He hired a couple of canoes and a crew of local Indians. During his stay the Amazon had a very serious flood. John realized that his actual mission was on hold, but a great many animals would be drowned. He put himself and his crew to work rescuing animals, taking them to high ground--not rare animals, but any animals they could reach. The work was perilous and very hard. John admitted that his crew considered him crazy, but he was paying them, and they considered themselves under the protection of the medal of the Blessed Virgin Mary, which John wore.
When the water receded, John and company returned to their base.

En route they passed a stretch of bank where two otters were feeding. As they passed, the otters rose on their hind legs and lifted their paws.

The foreman cried, "Loku gwamba! Loku gwamba! (Look at the animals) Gwamba say tank you John. But you no hear. Only God hear gwamba."

My source for this story is either an issue of National Geographic or an issue of Life from either the 1960's or 1970's. My memory fails me for the exact time or the magazine, but I remember the story with great clarity.