Montshire Minute: Amphibians

Originally aired during the week of June 21, 1999

Monday

Sometimes the leopard frog is called the grass frog or the meadow frog, because it tends to wander away from water during the summer. The adult leopard frog averages about three inches in length, is green in color, and has two or three irregular rows of roundish, black spots. The pickeral frog is another common species which has black markings that are more square in shape. In the spring, female leopard frogs lay about 3000 eggs in a loose mass in shallow water. By this time of year, the tadpoles that hatched are well on their way to becoming full-fledged frogs. The northern leopard frog is one of the critters naturalist Ted Levin expects to find when he takes us on a two-day exploration into the natural history of the Connecticut Valley region on June 30 and July 2. Call the Museum if you're interested in joining us!

Tuesday

Leopard frogs emerge from underwater hibernation in spring. From mid-April to mid-May the males rest, with limbs spread out, on the surface in the shallows of ponds and vegetated coves in lakes. After about ten days, the essentially round frog egg develops into a tadpole, which ventures out of the protective jelly and into the water. Feeding on algae and breathing through gills, the fully-grown tadpole is almost perfectly fish-like. One of the first signs of adulthood is the appearance of hind limbs. The tadpole also begins to depend more on its developing lungs than its gills to breathe. It increasingly lingers near the surface of the water to fill its newly formed lungs with air. Soon, the animal has well-developed front legs and a head that is clearly becoming more frog-like. The full-fledged frog will only have a tail stump as a reminder of its fish-like larval stage.

Wednesday

Few creatures undergo such a dramatic transformation from egg to adult as frogs and toads. The tadpole is almost totally fish-like, but it will eventually develop into a four-legged land dweller. The tadpole feeds entirely off tiny plant-life like algae, unlike the adult frog, which is an omnivore (that is, it eats plants and animals like worms and insects.) Event the frog's heart undergoes dramatic change, transforming from the two-chambered organ typical of fish to a three-chambered one. In his book The Life of the Pond, William Amos observes that the metamorphosis of the frog from egg to adult resembles the changes required when backboned animals left the water and took up life on land. That process was accomplished over millions of years - the frog completes a similar transformation in a few months.

Thursday

Ancestors of modern frogs lives tens of millions of years ago, when dinosaurs were kicking around. And they are still here today. What's the secret of their success? Well, as amphibians, frogs live in water, but they also get around just fine on land, thank you very much. They can escape from land predators by jumping into water (many frogs can jump 20 times their body length in one leap!) And if there's not much to eat in the water, they can find dinner on shore. Frogs live in many different climates and can be found pretty much any place where there's fresh water. During the cold winters, many species of frog hibernate, burrowing deep in the mud at the pond's bottom. As the temperature drops below freezing, the frog's breathing and heartbeat grind to a halt. When spring finally arrives, the frog's vital signs rebound. It emerges from the mud and continues on its happy-go-lucky way.

Friday

This week on the program, we've been examining the amazing life cycle of frogs. The female peeper lays her jelly-coated eggs separately on leaves and stems of water plants in shallow water, a process that can take weeks to complete. Other species, like leopard frogs and bullfrogs, lay their eggs in large masses which float in the water. The bullfrog, which does not begin mating until June or July, can lay a mass of twenty-thousand or so measuring two to five feet across. Looking at the eggs of a frog close up reveals a translucent ball of jelly about as large as a pea, which surrounds and protects the egg. The egg itself looks like a round, black nucleus. The northern leopard frog is one of the critters naturalist Ted Levin expects to find when he takes us on a two-day exploration into the natural history of the Connecticut Valley region on June 30 and July 2. Call the Museum if you're interested in joining us!