Amphibians
Four-toed Salamander
Hemidactylium scutatum · also called four-toed sally
The four-toed salamander is a small, easily missed amphibian with three quiet oddities: it is missing a toe, its tail is built to snap off on purpose, and it lays its eggs in nurseries shared by dozens of mothers.
Overview
Hemidactylium scutatum lives in mossy wetlands across eastern North America — sphagnum bogs, wooded seeps, and the edges of woodland pools. It is a slender lungless salamander, 5–9 cm long, brownish above with a striking white, black-spotted belly. It eats tiny litter invertebrates.
The missing toe and the breakaway tail
It has four toes on each hind foot instead of five. And at the base of the tail there is a sharp constriction — a pre-set fracture point. Seized, the salamander sheds the tail cleanly there; it thrashes to distract the predator and is later regrown.
Shared nurseries
Females lay their eggs in moss overhanging shallow water, and many females use the same site, so one hummock can hold dozens of clutches with attending females curled among them. The hatchling larvae drop into the water, and after just a few weeks leave it for good.
Status
Least Concern globally but declining and locally rare, because it depends entirely on undisturbed mossy wetlands that are easily drained or shaded out.
Four-toed Salamander: common questions
Why does the four-toed salamander have only four toes?
Reduction or loss of the fifth toe has happened independently in several groups of small, slender, ground-dwelling salamanders, and it is generally associated with a lifestyle of moving through leaf litter, moss, and soil rather than climbing or swimming, where a fifth toe adds little. In this species the four-toed hind foot is consistent and diagnostic, and it is paired with a compact body and a short trip through the aquatic larval stage. It is one of several features, along with the constricted tail and the white spotted belly, that set the four-toed salamander apart from the many similar-looking lungless salamanders it shares its habitat with.
What is the constriction at the base of the tail for?
It is a designed weak point for tail autotomy, the deliberate shedding of the tail to escape a predator. Many salamanders can drop their tails, but the four-toed salamander has taken it further, with an obvious groove where the tail meets the body and specialised tissue there that lets the tail separate cleanly with little blood loss. A grabbed salamander sheds the tail, which then writhes energetically on the ground for a minute or more, holding the predator's attention while the salamander crawls away. The tail regrows over the following months, though the replacement is usually shorter and slightly different in shape.
Why do several females share one nest?
Communal nesting is well documented in this species, with anywhere from a few to more than a hundred clutches recorded at a single favourable site. The likely reasons are that suitable nest moss overhanging water is limited, so females are drawn to the same good spots, and that clustering may dilute the risk of any one clutch being eaten and may keep the eggs from drying out. One or more females typically stay with the mass, and an attending female will curl around the eggs and has been shown to reduce fungal infection, so the young benefit from the guarding even if it is not their own mother providing it.
Is it dangerous, and can I keep one?
It is completely harmless to people; it has no venom, cannot bite through skin, and its mild skin secretions only make it unpalatable to small predators. It is also a poor choice as a pet. It is tiny, secretive, needs a cool, permanently moist, moss-rich setup and a constant supply of very small live prey, and it is easily harmed by handling. In several states it is protected. Because it is an indicator of healthy mossy wetlands, the most useful thing anyone can do for the four-toed salamander is to leave those wetlands intact.