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1 March 2007 Orientation of Juvenile Wood Frogs, Rana Sylvatica, Leaving Experimental Ponds
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Some amphibians are able to orient toward habitat features, but it is not always clear whether (1) these animals can directly detect the habitat toward which they are moving (e.g., scenting water from a wetland); or (2) they are detecting an indirect cue that is consistently correlated with the location of suitable habitat (e.g., the location of sunrise). In 2004, we translocated 400 Rana sylvatica tadpoles from an isolated population on Sears Island in Maine, where emerging metamorphs travel northeast towards a forested wetland. We placed study animals in arrays consisting of a central artificial pool, with a circular drift fence at 0.2 m from the pool's edge to assess orientation of metamorphs at emergence and a similar fence at 5 m to assess orientation postemergence. Arrays were placed at 10 m and 50 m from a forested wetland, with the wetland cue to the southwest (i.e., the opposite direction of the wetland at Sears Island). Rana sylvatica exhibited significant orientation toward the northeast at the 0.2 m fence, indicating that emerging metamorphs retained the same directionality as at the site where they were hatched. A significant result at the 5 m fence indicated that animals continued to head toward the northeast. These results suggest that the population of Rana sylvatica on Sears Island may rely on indirect cues for orientation. Relying on indirect cues offers less adaptability to changes in habitat such as breeding site loss or road construction, and thus could lead frogs into ecological traps.

David A. Patrick, Aram J. K. Calhoun, and Malcolm L. Hunter "Orientation of Juvenile Wood Frogs, Rana Sylvatica, Leaving Experimental Ponds," Journal of Herpetology 41(1), 158-163, (1 March 2007).[158:OOJWFR]2.0.CO;2
Accepted: 1 October 2006; Published: 1 March 2007

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