A Day in the Life of a Marbled Salamander
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Amphibian populations are noted for extreme year-to-year and site-to-site variation in population size and species composition. I believe the best way to understand this variation is to manipulate. Marbled salamander populations at several isolated, temporary wetlands on the Savannah River Site have been subjected to experimental manipulations in order to develop a better understanding of the primary mechanisms underlying population fluctuations: competition, predation, and hydroperiod. |
Manipulations were initiated in large-scale field enclosures at Ginger's Bay in September 1985. Experiments from 1985 to 1988 collectively demonstrated the significant effects that the number of larvae in a pond (larval density) has on important larval traits such as survival and size. Similar experiments in the 90's have addressed the impacts of invertebrate predation, timing of pond-filling, and two-species interactions. A common theme through all experiments is that conditions in the aquatic environment continue to affect individuals post-metamorphosis; i.e., in the terrestrial stage of the life cycle. The extent to which populations are influenced by conditions in the forests surrounding the wetlands is largely unknown. However, a population model based on the experimental and observational data suggests that the terrestrial habitat conditions may have stronger impacts on the population dynamics than some aquatic parameters. Because the natural history of Ambystoma opacum at Ginger's Bay has been so well-studied (including nesting behavior, reproductive behavior, and genetic structure), researchers are able to develop management plans and assess risk to the population from a strong ecological data base.