Wood frog

The wood frog lives in the woods.

It is often brown or tan. This helps it hide on the ground.

These frogs are very special. They can freeze in the cold winter. They stay safe under dead leaves.

When it gets cold, their bodies make food. This food helps them stay safe. It stops ice from hurting them.

In the spring, they come out. They go to small pools of water. They make a quacking sound.

The tiny babies live in the water. They eat plants and tiny bits of food. They grow into new frogs.

The wood frog lives in forests across North America.

They are often brown, tan, or rust-colored. This helps them hide on the forest floor. Some frogs can even change their color.

These frogs have a special way to survive winter. They can freeze solid! To stay safe, they build up urea in their bodies. Urea is a substance that helps limit ice. They also turn liver glycogen into glucose. Glucose is a type of sugar that acts as a cryoprotectant. This means it protects their cells from ice damage. When frozen, the frog has no heartbeat or breathing. They can stay frozen for many days.

In early spring, they wake up. They move to small, shallow pools called vernal pools.

These pools are great because they have no fish. This keeps the eggs and tadpoles safe. The males make duck-like quacking sounds to find mates. Most wood frogs only breed once in their lives. They are very important to the forest woods.

The wood frog is a special kind of amphibian found across North America.

These frogs live in many places, from the boreal forests of the north to the southern Appalachians. They are very good at living on land compared to other frogs. Most wood frogs spend their time on the forest floor. They can be brown, tan, or rust-colored to hide in the leaves.

They can even change their color depending on the season or sunlight. Some frogs might look light brown at one time and dark brown at another.

These frogs have a truly amazing way to survive the cold winter. They can actually freeze solid and still stay alive. To get ready, they build up urea in their bodies. They also turn liver glycogen into glucose, which is a type of sugar. These substances act as cryoprotectants, which are things that protect cells from ice damage.

When they are frozen, they have no heartbeat or breathing. They can stay frozen for about 193 days in a row. This helps them survive in very cold places like Interior Alaska.

Scientists have studied these frogs to learn how they handle the ice. Researchers have looked at how wood frogs use different parts of their bodies to stay safe. For example, they have a special enzyme called SERCA 1 that works well in the cold.

Some studies show that frogs in Alaska have even more sugar and urea than others. This helps them survive even more extreme freezing. People also study how they move between different habitats. This helps us understand how to protect them and their homes.

Wood frogs live in many different types of forest areas.

They are the most common frog found in Alaska. They also live in the Medicine Bow National Forest. Many wood frogs breed in small, shallow pools called vernal pools. These pools are not permanent and can dry up over time. In the east, they live from northern Georgia to northeastern Canada. In the west, they reach from Alaska to southern British Columbia.

Learning about wood frogs helps us understand how nature works. They are "explosive breeders," which means many frogs mate in just one week. Males make duck-like quacking sounds to find females in the spring. The females lay eggs on plants or branches under the water. These eggs grow into tadpoles that eat algae and tiny bits of plants. Most young frogs stay near the pool where they were born. However, a few will move to new areas to find new homes. This cycle keeps the forest healthy and full of life.

The wood frog, known scientifically as *Lithobates sylvaticus*, is a remarkable amphibian species.

It is found across a massive portion of North America. Its range stretches from the boreal forests of Canada to the southern Appalachians. In the west, it reaches from Alaska to southern British Columbia. This frog is highly significant to biologists because of its unique survival skills. It can tolerate freezing temperatures that would kill most other animals. It is also a very terrestrial frog, meaning it spends much of its life on land.

Because it relies on specific types of wetlands, it is a key species for studying ecology.

To survive harsh winters, the wood frog uses a complex biological process. As winter approaches, the frog accumulates urea in its body tissues. It also converts liver glycogen, which is stored energy, into glucose, a type of sugar. Both urea and glucose act as cryoprotectants. These substances help limit ice formation and prevent cells from shrinking too much.

When the frog freezes, ice forms in its body water. The frog can tolerate the freezing of 65% to 70% of its total body water. During this time, the frog has no detectable heartbeat, breathing, or brain activity. It remains in this frozen state for an average of 193 days. This allows it to survive in extreme environments like Interior Alaska.

Wood frogs have different physical characteristics depending on their environment and season. Most adults are brown, tan, or rust-colored to help them hide. They often have a dark mask over their eyes.

Their skin color can actually change based on sunlight exposure. Sunlight can cause their skin to darken. Some individuals have been observed changing from light brown to dark brown. Their underparts are usually pale with a yellow or green tint. In northern populations, the belly might have a mottled pattern. These variations help them blend into the forest floor.

Scientists have discovered specific evolutionary adaptations that make this freeze tolerance possible. One key mechanism involves a specific enzyme called SERCA 1. This enzyme is a protein pump that helps manage calcium in cells. In wood frogs, a series of seven amino acid substitutions allows this pump to function at very low temperatures.

This is different from related species like the green frog, which cannot work as well in the cold. Researchers have also found that Alaskan wood frogs have larger liver glycogen reserves. They also produce more urea than frogs in warmer areas. These specific adaptations help them survive the most extreme northern climates.

Reproduction for the wood frog is an intense and rapid event. They are known as "explosive breeders" because many frogs mate within a single week. This usually happens in early spring right as the snow melts. Males move through the water making duck-like quacking sounds to attract females. When a male finds a female, he uses a hold called amplexus. He clasps her from behind her forearms to hold her until she lays her eggs. The female attaches the eggs to underwater plants or fallen branches. Often, many eggs are laid together in large groups to increase their chances of survival.

Wood frogs prefer to breed in ephemeral wetlands known as vernal pools. These are freshwater pools that are not permanent and eventually dry up. This habitat provides a special advantage against predators. Most fish cannot live in these temporary pools, so the eggs and tadpoles are safer. However, there is a risk that the pool might dry up before the tadpoles can grow into frogs. The tadpoles are omnivores that eat algae and plant bits. They must grow quickly to reach the next stage of life before the water disappears.

The life cycle of the wood frog is closely tied to the health of the forest. Most young frogs are philopatric, meaning they stay near the pool where they were born. Only about 20% of juveniles move away to find new breeding sites. Because they rely on these specific pools, the species is sensitive to environmental changes. For example, road salts used for de-icing can be toxic to larvae. Studies show that salt can cause lower weight and physical abnormalities in tadpoles. Protecting the wide landscape of forests and wetlands is essential for their survival.