Amphibian activity, movement patterns, and body size in fragmented peat bogs

I investigated the activity, direction of movement, and body size (snout-vent length) of amphibians in both pristine and fragmented bogs of southeastern New Brunswick. I used drift-fences with pitfall traps to capture amphibians in six pristine bogs and six bogs undergoing peat mining (i.e, bog fragments) in 1997 and 1998. Results indicate that seasonal activity patterns of amphibians in bogs peak during August and correspond to movements of adults (following breeding) and juveniles (after metamorphosis) from adjacent wetlands. A seasonal shift in species composition occurred, as most captures early in the season consisted almost exclusively of ranids, with an increase in salamander captures in late summer and fall. Climatic variables generally explained more of the variation in amphibian activity in fragments than in pristine bogs. Wood frog activity near fragment edges was more dependent on amount of precipitation than in pristine bogs. Wood frog and green frog movements were nonrandomly oriented relative to mined fragment edges. Orientation of leopard frog movements was strongly influenced by year. Wood frogs occurring in fragments were larger than those in pristine bogs. The size difference in green frogs was not significant but followed the same patterns as wood frogs. Leopard frogs within bog fragments were larger than those in pristine bogs but only in 1998. This study implies that peat mining influences amphibian activity and movement patterns in neighboring bog fragments. Larger individuals may be better suited for survival in disturbed environments, such as mined bogs, because they are less sensitive to desiccation than smaller ones.