The four-toed salamander (Hemidactylium scutatum) is one of eight salamander species inhabiting Minnesota. It is unique in multiple ways. The first is the four toes on its hind feet. Most other Minnesota salamanders have five toes in back. All have four toes in front. It is 3-5 inches long, red-brown with dark flecks on its sides, has a bright white belly with black mottling, and an obvious tail constriction. First discovered in Minnesota in Itasca County in 1994, it is now also known in Aitkin, St. Louis, Carlton, Pine and Mille Lacs counties.
This native is distributed widely in disjunct and isolated populations across eastern North America’s mature, upland, deciduous or deciduous-coniferous forests intermixed with bogs, alder swamps, vernal ponds or other fishless wetlands (fish eat salamanders and compete with them for food). Belonging to a family of lungless salamanders, four-toed adults are limited to damp habitats and moist weather, so oxygen and carbon dioxide can dissolve and move across its skin – another unique feature. Mature closed-canopy forests with temporary and seasonal wetlands afford the shade, temperature, moisture, organic soils, woody debris, moss, suitable nesting and overwintering places, and habitat corridors they need to survive and thrive.
Tougher Than A Dinosaur
In Minnesota, the four-toed salamander is listed as a species of special concern due to its tendency to occur in small isolated colonies and thus be vulnerable to catastrophic events or drastic habitat changes. However, it seems they coexisted with dinosaurs for 75 million years and survived the mass dinosaur extinction. Its genus is apparently the oldest of all lungless salamanders, and since four-toeds are the only species in it, they are the sole representative of many millions of years of evolution!
It’s A Complex Life
The life cycle of a four-toed salamander is a little complex. Like most amphibians, it lives a double life as shell-less eggs and gilled larvae in water, then as adults on land. The cycle begins in fall when males and females court in an intriguing ‘tail-straddle walk’ prior to the male depositing sperm that the female picks up with her cloaca. In late fall, they gather to winter in below ground hideaways. Females laden with eggs emerge in late April to early May, journeying to wetlands to lay about 30 eggs, or communally lay hundreds of eggs, at land’s edge in moss hummocks, grass clumps, under bark, the base of alders or other protected sites.
At least one female stays with each nest for four to six weeks until larvae emerge. Her main role seems to be protection of the embryos from fungal pathogens, not predators. Microflora living on the female’s skin transmit valuable bacteria to the embryos that offer antibodies and natural immunity to chytrid fungus. This fungus has devastated and caused extinction for other amphibian species. The eggs are believed to have a toxin that makes them distasteful to predators.
Toxins and Trick Tails
After four-toed larvae emerge, they wriggle and plop into the water to feed on zooplankton and other small aquatic invertebrates. The optimal water depth is roughly 20 inches to give sufficient moisture during the six weeks they metamorphose, but be too shallow and temporary for fish to inhabit. As ‘mini adults’, they climb onto land and disperse two to three weeks later. At about two years of age they can reproduce. Adults eat small invertebrates such as ticks, ants, beetles, spiders, snails and worms. When they become prey, they secrete toxins, and unlike most other species, can detach their tail at will, even before grabbed – yet another amazing feature! These exceptional creatures can live at least 9 years.
Helping Habitat Hand
To give these cool creatures a hand, forest landowners that know or think they may be providing a home for them or other salamanders can help by using the following conservation actions. First, as always encouraged, we can keep our forests in large, un-fragmented, un-developed, native, diverse, healthy patches. Next, we can minimize roads and trails so they are less likely to be barriers to four toed movement; locate roads and trails on uplands to prevent run-off and erosion into wetlands and streams; eliminate use of chemicals such as herbicides and insecticides; and protect known and potential nesting sites by keeping fish out. Finally, when conducting timber harvest, we can: protect nesting sites by creating a no or light harvest buffer around them (50 feet of no harvest suggested, plus an additional 50-150 feet with 80% residual basal cover left); harvest between October 1 to March 15 to protect migrating and dispersing four-toeds; harvest and do prep (such as trail establishment) on frozen ground to reduce soil compaction and rutting (protects burrows); assess and mark forests in spring and early summer when nesting sites are most identifiable; and distribute slash across the site to provide woody debris and prevent large piles from blocking four-toed movements. Our thoughtful practices will also benefit other forest wildlife needing similar habitats.
Because they are a rare species in Minnesota, please report four-toed salamander sightings to MN DNR by phone (Minnesota Biological Survey’s animal report line at 1-888-345-1730) or e-mail (email@example.com, subject line of “Four-toed Salamander Report”). The date, location, observer, and contact information are important, and photos helpful. To support amphibian research and conservation globally and in Minnesota, considering recording your observations at HerpMapper (www.herpmapper.org). To learn more, the guide “Amphibians and Reptiles in Minnesota” by John Moriarty and Carol Hall (2014) is an excellent resource.
Thank you to Minnesota amphibian experts who reviewed and provided information for this article: Carol Hall, Erica Hoaglund, Jeff LeClere, and Luke Groff of MN DNR, and Chris Smith of MN DOT.