Wood frogs are a medium-sized frog measuring about 2- 3 inches with the females being larger as is typical with most species of frogs and toads. No other frog looks like the wood frog in North America. They range in color from a light tan to brown and rust colored. They usually have a dark eye mask like a raccoon and are slightly green on their belly.

The reason their colors vary so widely is the frogs of that region have adapted to the local leaf litter and vegetation that best suits their survival. Frogs from peat bogs without many trees in parts of Canada show darker colors, whereas frogs from areas with lots of pine trees show the lighter colors because of the tan pine needles that litter the ground.

Wood frogs have a wide distribution and are found throughout the northeastern US, Canada, and Alaska. Wood frogs live in moist woodlands, bogs, freshwater wetlands, and swamps. They are more terrestrial than other frogs and spend a lot of time on land. This makes sense considering they breed and reproduce in temporary pools and bodies of water. When the water dries up, they need to survive until it returns. When they are on land, they will stay in areas with more moisture like ravines and heavily forested shady areas.

Because of their wide distribution all over Canada and parts of the US, wood frogs have a highly varied diet. They are insectivores and will eat pretty much any small forest floor invertebrate they can overpower. This includes beetles, ants, worms, grubs, isopods or “rolie pollies”, millipedes, and anything else they can catch.

Like most frogs, they hunt based on movement of their prey. To catch them, they wait patiently until something comes nearby and then lunge forward and use the tip of their tongue to grip them and bring the prey into the mouth. They will then swallow their prey whole. Wood frogs close their eyes when they swallow because it helps push the food down their throats.

As tadpoles, they are herbivores and will eat primarily algae but sometimes, if resources are scarce, feed on the eggs of other tadpoles. Once the tadpoles transform into little froglets and emerge from the water, they switch to their carnivorous diet.

This transformation from a complete herbivore to a carnivore is perhaps one of the most dramatic changes in anatomy and physiology in the animal kingdom. The tadpole’s digestive tract is very long and convoluted so they can process the algae’s thick cell wall, whereas the carnivorous adults have short and simple intestines with strong stomach acids that quickly digest insects and invertebrates.

Like most frogs, they start that life as a humble tadpole. For wood frogs, especially in Alaska, adults need to mate, lay eggs, the eggs need to hatch, and go from tadpoles to adults within 5 months.

When they are ready to reproduce, they will thaw out from their winter hibernation and find the nearest body of water.

Wood frogs prefer to breed in ephemeral wetlands or vernal pools. These are places that temporarily hold water after heavy rain or snow melt. The reason the frogs choose these areas is actually a smart survival tactic as they are usually free of fish and other predators, which the perfect place for tadpoles to grow up.

The risk with laying eggs in these types of pools is there is always a chance they will dry up. This is why the wood frog lays eggs so early because the chance of evaporation is reduced earlier in the season since there is more rain and lower outside temperatures in the early spring.

Wood frogs are also some of the very first frogs to emerge in the spring, and the earlier they get started, the better chance their offspring have at surviving. This is the reason scientists think they freeze instead of hibernate at the bottom of a pond or lake.

Once they find a good pool of water, the frogs will begin calling to each other. Once a male and female locate each other, the male will grasp around her waist and lock his thumbs together in a position called amplexus, it looks much like he is hugging her. As she lays her eggs, he will fertilize them in this position. Oftentimes frogs will lay eggs near other frogs and create large masses of eggs to ensure even better odds of survival for the tadpoles.

Once the eggs are laid, their rate of development depends on temperature, population density of other tadpoles, and the abundance of food. Depending on temperature, the eggs hatch in a few days to weeks and tiny tadpoles swim out.

If the pools are crowded and warm, the tadpoles will develop faster than normal. If they are cool, large, and sparsely populated with plenty of food, they can take their time and grow larger and stronger. In about 2-4 months, the tadpoles will develop into tiny froglets before jumping out of the water as adults.

Most of the adult frogs will come back to this same pool to breed. Only about 20% will migrate to other areas. It is this 20% that have spread the population all over Canada and Alaska, which means they are key to the species’ expansion and distribution.

They are one of the only amphibians that live near the Arctic Circle.

Most frogs and amphibians will cope with winter by either burying themselves in the ground or stay at the bottoms of lakes and ponds. Their metabolism drops so low, they do not need to breathe air or eat and get all of the oxygen they need by breathing through their highly absorbent skin. But most frogs don’t deal with the kind of long winters that wood frogs must endure. This is why wood frogs have an even more extreme and successful way of dealing with the icy winter, they freeze almost completely solid.

They can survive in this state off and on for 7 months in temperatures as low as 3°F! Their heart stops beating, blood stops flowing, and they go into suspended animation. Their individual cells are still functioning but they have no way of communicating with each other. When the spring rolls around, they thaw from the inside out. The heart and brain will thaw first because of the high concentrations of antifreeze and then eventually the limbs come last.

By thawing from the inside first, they can gain full consciousness and be ready to hop away as soon as their limbs catch up to their brain and body. They do this by producing their own antifreeze in the form of glucose and urea. Their liver converts glycogen into glucose (sugar) that builds up in their tissues; this prevents ice crystals from forming in their body. They may appear frozen solid when you pick them up, but their body is only about 65% frozen.

Scientists discovered another strategy the frog uses to stay alive. During the winter day, the temperature is slightly warmer. Wood frogs thaw a little and use this opportunity to build up and produce even more antifreeze. So as the winter goes on, they build up more and more to make sure they stay alive. Once the spring is in full swing, they hop into a pond and do some spring cleaning by flushing out all of the built-up glucose and urea.