Tuesday, January 09, 2007

Mystery Crayfish

The mystery was not what creature had previously been constructed of the parts, but what creature had deposited the parts onto the boardwalk. The collection of crayfish parts shown in the image was discovered on the boardwalk 50 meters from the nature center. Detective work is one of the enjoyable aspects of our work as naturalists.

Several animals eat crayfish here in the swamp including River Otters, Yellow-crowned Night Herons, Raccoons, White Ibis, and Barred Owls. By looking at the pile of parts, it could be seen that the majority of the pieces were bound together as if they had been squeezed in the one's palm or constricted in an esophagus. The parts did not appear discolored (orange/pink) as one might expect if they had traveled through a digestive system or boiled in a pot. There were no signs in the crayfish parts of other fecal matter or the distinctive white material produced by a bird's urinary system. Therefore, it is unlikely that the pile of crayfish parts came from an otter, a heron, a raccoon, or an ibis as all these animals would pass the indigestible portions of their meals completely through their digestive system. As owls regurgitate the indigestible parts of their meals (hair, bones, scales, exoskeletons), we concluded that a Barred Owl (Strix varia) perched on the handrail (where there was a quantity of white bird waste) after consuming several crayfish and then relieved itself before flying off. The crayfish parts were still quite moist, so we did not miss seeing the owl by much.

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