---
title: "What the sources say about the Wood Frog | AnimalTracks.wiki"
description: "41 claims from the Wood Frog profile, each beside the words of the source that backs it."
image: "https://animaltracks.wiki/images/animals/wood-frog-1.webp"
canonical: "https://animaltracks.wiki/animals/wood-frog/sources/"
---

# What the sources say about the Wood Frog (*Lithobates sylvaticus*)

> 41 claims from the Wood Frog profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Wood Frog](https://animaltracks.wiki/animals/wood-frog/)

## Lithobates sylvaticus (wood frog). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Lithobates_sylvaticus/

| The page says | The source says |
| :--- | :--- |
| As much as 35 to 45 percent of its body turns to ice beneath the skin | as much as 35 to 45% of a frog's body may freeze and turn to ice. Ice crystals form beneath the skin |
| its breathing, blood flow, and heartbeat stop | During the freeze the frog's breathing, blood flow, and heart beat cease. |
| That sugar, combined with specialized proteins, keeps the water inside each cell from crystallizing while ice fills the spaces outside it | Freezing is made possible by specialized proteins and glucose, which prevent intracellular freezing and dehydration. |
| Wood frogs live in tundra, bogs, and coniferous or deciduous forest | Wood frogs inhabit a wide variety of habitats including tundra, thickets, wet meadows, bogs, coniferous and deciduous forests. |
| found from northern Georgia to Alaska | They are found from northern Georgia and in isolated colonies in the central highlands in the eastern to central parts of Alabama, up through the northeastern United States, and all the way across Canada into Alaska. |
| They are found farther north than any other reptile or amphibian in North America | They are found farther north than any other North American reptile or amphibian. |
| average about 8 grams | Average mass 7.88 g (note: ADW displays this figure sourced from the AnAge database on its own page; rounded from 7.88 g.) |
| A black patch runs from each wood frog's eardrum to the base of the front leg, earning the species the nickname "robber's mask," | they can be distinguished by a black patch that extends over the tympanum to the base of the front limb. It is this characteristic that causes them to be referred to as the frog with the "robber's mask". |
| against skin that's usually rust-brown or tan, but sometimes green or gray | This species exhibits a number of color morphs, usually browns, tans and rust, but can also be found in shades of green and gray. |
| Adults eat small invertebrates, especially spiders, beetles, moth caterpillars, slugs, and snails | Adult wood frogs eat a variety of terrestrial insects and other small invertebrates, especially spiders (Order Araneae), beetles (Order Coleoptera), moth larvae (Order lepidoptera), slugs (Order Stylommatophora) and snails (Order Stylommatophora). |
| Wood frogs are the first frogs of the year to start calling, often before the ice is completely off their breeding ponds | They are the first frogs to begin calling, often before the ice is completely off the breeding ponds. |
| filling the air with a chorus of duck-like quacking some describe as "a lot of chuckling" | they create a chorus of duck-like quacking sounds, described by some as a "lot of chuckling". |
| Each female lays a globular mass of 1,000 to 3,000 eggs, 10 to 13 centimeters across | the female will lay a globular egg mass ... Each egg mass measures about 10 to 13 cm in diameter, and can contain from 1000 to 3000 eggs. |
| Numerous small green algae then turn the jelly around the eggs green, which makes a great camouflage | The jelly around the eggs becomes green in color creating a great camouflage. The green color of the jelly is due to the presence of numerous small green algae. |
| Wood frog tadpoles have the strongest kin recognition yet discovered in amphibian larvae | Wood frog tadpoles have been shown to have the strongest powers of kin recognition yet discovered in amphibian larvae. |
| Researchers marked tadpoles with dye and released them into natural habitats, and siblings sought each other out and regrouped together | They have been documented (by marking them with dye and releasing them into natural habitats) to aggregate back together. |
| which may help them find food, keep warm, and avoid predators | This may be a survival mechanism allowing them the potential benefit of food, thermoregulation, and defense against predators. |
| Adult wood frogs produce noxious skin secretions, though these only seem to deter shrews | Adult wood frogs have noxious skin secretions but they are only effective in deterring shrews. |
| the frog may let out a piercing cry that startles its attacker into loosening its grip | If captured, wood frogs may emit a piercing cry that may startle the attacker enough to release the frog. |
| A frog that can let ice fill over a third of its body each winter, stop its own heart, and thaw out alive again each spring | as much as 35 to 45% of a frog's body may freeze and turn to ice (note: Tagline; restates the freeze-percentage and heart-stop claims made in the body (35-45% rounds to "over a third").) |
| Tundra, bogs, and coniferous or deciduous forest | Wood frogs inhabit a wide variety of habitats including tundra, thickets, wet meadows, bogs, coniferous and deciduous forests. (note: stats.habitat, first clause.) |
| farther north than any other North American reptile or amphibian | They are found farther north than any other North American reptile or amphibian. (note: stats.habitat, second clause.) |
| First to Call, Camouflaged as Eggs | They are the first frogs to begin calling, often before the ice is completely off the breeding ponds. (note: Heading; 'camouflaged as eggs' refers to the green egg-mass jelly claimed later in the section.) |
| In winter, the wood frog (*Lithobates sylvaticus*) freezes while it hibernates | Wood frogs utilize a cryogenic freezing process during hibernation. In the winter, |
| While a wood frog is frozen, its breathing, blood flow and heartbeat all stop. | During the freeze the frog's breathing, blood flow, and heart beat cease. |

## Wood Frog. National Wildlife Federation.

https://www.nwf.org/Educational-Resources/Wildlife-Guide/Amphibians/Wood-Frog

| The page says | The source says |
| :--- | :--- |
| Ice forming inside its cells would be deadly | Their bodies produce a special antifreeze substance that prevents ice from freezing within their cells, which would be deadly. |
| reaching north of the Arctic Circle | Wood frogs are the only frogs that live north of the Arctic Circle. (note: Only the range fact is used. NWF's 'only frogs' superlative is cut: common and moor frogs also range north of the Arctic Circle in Eurasia.) |
| Adults run 3.8 to 8.2 centimeters long | Adults of this amphibian species are 1.5 to 3.25 inches (3.8 to 8.2 centimeters) in length. |
| usually live no more than three years in the wild | A wood frog's lifespan in the wild is usually no more than three years. |
| Ice forms in the spaces between the frog's cells, not inside them, where it would be deadly | prevents ice from freezing within their cells, which would be deadly. Ice does form, however, in the spaces between the cells. |

## Larson et al. (2014). Wood frog adaptations to overwintering in Alaska: New limits to freezing tolerance. Journal of Experimental Biology.

https://doi.org/10.1242/jeb.101931

| The page says | The source says |
| :--- | :--- |
| Wood frogs in Interior Alaska survive freezing to more extreme limits and durations than the populations studied in southern Canada and the Midwestern United States | Wood frogs in Interior Alaska survive freezing to extreme limits and durations compared with those described in animals collected in southern Canada or the Midwestern United States. |
| Tracked into their natural hibernacula, they stayed frozen for 193 days on average | tracking animals into natural hibernacula ... Wood frogs in natural hibernacula remained frozen for 193 ± 11 consecutive days |
| through average minimum temperatures of -14.6°C and as low as -18.1°C, and all 18 of the frogs tracked survived the winter | average minimum temperatures of -14.6 ± 2.8°C (range -8.9 to -18.1°C) with 100% survival (N=18) |
| Their muscles held glucose levels 13 times higher, and their hearts 10 times higher, than frogs frozen in a laboratory | Mean glucose concentrations were 13-fold higher in muscle, 10-fold higher in heart and 3.3-fold higher in liver in naturally freezing compared with laboratory frozen frogs. |
| Researchers think that extra glucose builds up through the repeated freezing and thawing these frogs go through in early autumn | We hypothesize that this enhancement of freeze tolerance in Alaskan wood frogs is due to higher cryoprotectant levels that are produced by repeated freezing and thawing cycles experienced under natural conditions during early autumn. |
| Six Months Frozen in Interior Alaska | remained frozen for 193 ± 11 consecutive days (note: Heading rounds 193 days to roughly six months.) |

## Storey (1997). Organic Solutes in Freezing Tolerance. Comparative Biochemistry and Physiology Part A: Physiology.

https://doi.org/10.1016/s0300-9629(96)00270-8

| The page says | The source says |
| :--- | :--- |
| when ice starts forming in its outer tissues, the frog's liver rapidly manufactures large amounts of glucose and distributes it through the body | freeze-tolerant frogs respond to ice formation in peripheral tissues by synthesizing large amounts of glucose in the liver and rapidly distributing the sugar throughout the body |
| When a frozen wood frog starts to warm up, its liver and heart melt before the rest of its body, letting its vital functions restart while the rest of the frog is still thawing | during thawing, organs such as liver and heart melted first, allowing recovery of their vital functions to begin while the rest of the frog thawed |
| Freeze-tolerant animals like the wood frog build up high levels of small dissolved solutes, such as sugars, which limit how much of the body's water turns to extracellular ice and how much each cell shrinks as water leaves it | The accumulation of high levels of low-molecular-weight solutes (polyhydric alcohols, saccharides) provides cryoprotection to freeze-tolerant animals by minimizing, via colligative effects, the percentage of body water converted to extracellular ice and the extent of cell volume reduction. |
| Liver and Heart Thaw First | during thawing, organs such as liver and heart melted first, allowing recovery of their vital functions to begin while the rest of the frog thawed (note: Blockquote lead-in, restating the claim below it.) |

## Lithobates sylvaticus. The IUCN Red List of Threatened Species 2022: e.T58728A193382501.

https://doi.org/10.2305/iucn.uk.2022-1.rlts.t58728a193382501.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN Red List category: Least Concern (LC). (note: Category read through GBIF's copy of the Red List, per the source pack; the claim cites the assessment DOI, not the GBIF API.) |