Long-toed Salamander

The name refers to a subtle but consistent anatomical feature, a noticeably elongated fourth toe on each of its hind feet compared to the toe proportions seen in most other members of the mole salamander genus, Ambystoma. While not something a casual observer would necessarily notice at a glance, this toe length became a useful and reliable identifying feature for herpetologists distinguishing it from similar-looking relatives, and it eventually gave the species both its English common name and its scientific species name, macrodactylum, which comes from Greek roots meaning large or long finger or toe.

It has an unusually broad tolerance for cold temperatures and short growing seasons compared to most other salamander species, allowing populations to persist in alpine meadows and high mountain lakes at elevations exceeding 2,700 metres in parts of its range, conditions that would be lethal or simply unsuitable for many other amphibians. High-elevation populations have adapted their breeding timing accordingly, migrating to breeding ponds and beginning to lay eggs as soon as the snow begins melting each spring, sometimes moving across still-present snow patches and breeding in water that remains partially ice-covered, to make the most of a very short window of warmer weather.

Genetic and morphological studies of populations isolated on certain islands after the retreat of glaciers at the end of the last ice age have revealed some striking differences compared to mainland populations, including notably larger average body size in a few isolated island groups. Researchers studying these differences see them as a useful natural experiment in rapid evolutionary change, since isolated populations facing different predator communities, competition levels, and resource availability on islands appear to have diverged in body size and possibly other life history traits within the roughly 10,000 to 14,000 years since glacial retreat, a relatively short span in evolutionary terms.

Diet changes considerably between the aquatic larval stage and the terrestrial adult stage, reflecting the very different environments each stage occupies. Larvae living in ponds and lakes feed on zooplankton, small aquatic invertebrates, and, particularly in ponds without fish, sometimes even on the larvae of other amphibian species sharing the same water, since they are active, effective aquatic predators despite their small size. After metamorphosis, adults move onto land and switch to hunting terrestrial invertebrates such as insects, worms, and other small prey found in the leaf litter and soil of forest floors and mountain meadows.