Arctic Amphibians
Wood Frog
The most northerly amphibian in North America, the wood frog has amazing freeze tolerance – it can survive even though much of its body fluids are frozen! Because of this adaptation, the wood frog has extended its range to the tree line, bordering on the Arctic. Perhaps climate is not what prevents this amazing animal from living even farther north, but simply the absence of its preferred habitat – damp, wooded areas. As its name suggests, the wood frog normally lives on the forest floor, stalking prey such as beetles or flies.
The wood frog is terrestrial most of the year, hibernating on land through the winter, and returning to ponds in the early spring while the ice is still present to mate. Males arrive first and produce a feeble quacking call to attract mates. Several females lay their eggs together, forming a communal mass that attaches to vegetation at the water's surface.
Birds
Early Birds=
Because the summer is so short, it is critical for birds to make the most of it by nesting as early as possible. Gyrfalcons get a head start by wintering in the Arctic, and thus have the first pick of nesting cliffs in spring. Early nesting means that their offspring are already leaving the nest, while other birds have only just hatched, ensuring a good supply of easy prey for the young falcons as they learn to hunt.
Geese do not winter in the Arctic, but return very early, often before the snow has left the tundra. They store up energy, feeding heavily in the south, because there is little or no food available when they reach their breeding grounds. By the time their eggs have hatched, however, summer has arrived and there is plenty of new vegetation to eat. Many shorebirds and ducks also nest early. Unable to leave their eggs exposed to the cold, females of the common eider duck do not eat or drink for a full month while they incubate their eggs! Once the young hatch they are cared for by "aunty" ducks, while the exhausted and half-starved females recuperate in preparation for their southward migration.
Fast Hatchers
Part of a young bird's development occurs inside the egg, and part of it occurs outside, after the chick has hatched. Different species of birds go through these two stages at different rates. Many groups of arctic birds, such as waterfowl and shorebirds, have precocial young, which complete most of their development inside the egg. Precocial young are covered in warm fuzz and can walk or swim and often feed themselves within hours of hatching. Other birds, particularly the "perching birds" such as pipits and buntings, have altricial young. These chicks hatch with their eyes closed, completely naked and helpless. They must be tended constantly by their parents for approximately two weeks.
Breeding in the Arctic has to be done in a hurry, because the summer is extremely short. The faster young can develop, the better. Although altricial hatchlings must be carefully fed, protected and kept warm, these chicks take much less time overall to develop than precocial young. Young snow buntings, for example, are fully grown and independent only 4 weeks after the eggs are laid, while the precocial young of semipalmated sandpipers, which are approximately the same size, take six weeks from egg laying to fledging.
Rapid development allows birds to mate, lay eggs, rear offspring and leave again in a very short window of time. This strategy is particularly important to the small arctic land birds, which cannot store enough food to survive periods of scarcity in the early spring or late fall. Although precocial birds take slightly longer overall to develop, these birds have a distinct advantage: they make better use of available food resources. These active chicks can scatter from the nest and search for food separately, so they don't compete with each other in the same small area – an advantage on the tundra, where food is more thinly distributed. Because they are fuzzy and can run away, they are also more able to escape predators, and less likely to get cold than naked hatchlings.
