satellite or microchip, salamanders navigate by a combination of
magnetic and chemical signals that herpetologists are just
beginning to understand.
Part of their direction-finding ability relies on a precise reading of
the lines in the earth’s magnetic field. A small organ in the brain
processes magnetic data and guides the salamander to its pond.
Though many other ponds and vernal pools lie along the route, they
will not stop until they arrive at the birthplace, struggling mightily to
get there. Once they are close, homing in salamanders seems to
be similar to salmon identifying their home river: they smell their
way with a nasal gland on their snouts. Following the earth’s
magnetic signals gets them to the neighborhood and then scent
takes over to guide them home. It’s like getting off an airplane and
then finding your way to your childhood home by following the
ineffable odor of Sunday dinner and your mother’s perfume.
On last year’s mission to the hollow, my daughter begged to follow
the salamanders and see where they were going. We trailed behind
by flashlight as the amphibians twined between scarlet stems of red
osier and clambered over flattened tussocks of sedge. They
stopped far short of the main pond, on the edges of a vernal pool, a
small depression in the land that goes unnoticed in summer but
reliably fills with snowmelt every spring, making a watery mosaic.
Salamanders choose these temporary basins to lay eggs because
they are too shallow and short-lived for fish, which would gobble up
the salamander larvae, to inhabit. The pool’s evanescence is the
newborn’s protection from fish.
We followed the salamanders to the water’s edge, where
platelets of ice still clung to the shore. They did not hesitate, but