Two weeks ago I sojourned to a distinct depression in an oak bottomland forest in central Virginia. Now dry as a bone, it looked little different from the surrounding forest—but a few Aprils ago, I had seen clouds of thousands of Marbled Salamander larvae here, in this very spot, when the depression was ponded with water about two feet deep. Sure enough, my rolls of two large logs produced five Marbled Salamanders (Ambystoma opacum), each ensconced in its own earthen cell. This find underscored that summer is becoming autumn, greatly comforting me.
During the breeding season the species is strikingly dimorphic in color—the females, in Oakland Raiders colors (black and silver) are now fat as ticks with eggs. The gorgeous males, skinnier but still plumpish, wear bright white bands over their shiny dark backs.
Among Ambystoma, Marbled Salamanders are different from most members of the genus in that they initiate breeding migrations in late summer to fall, with females laying their eggs terrestrially at sites in the pond basin where rising water levels (only if it rains, that is!) will later flood them. Interestingly, field studies have shown that more northerly opacum (e.g., Virginia to New England) begin their movements to breeding ponds about a month earlier (on average September to October) than Marbleds in the Deep South (October to November in South Carolina, Georgia and North Florida).
The imperiled Flatwoods Salamanders (Ambystoma bishopi and A. cingulatum) also migrate in the fall and also deposit eggs on land.
Check out March of the Salamanders for more about Marbled Salamander and Flatwoods Salamander migration.