Nature Notes

Northern Leopard Frog

45 degrees, it’s a magic number! or temperature rather. In the spring, when the nighttime temperatures are above 45 degrees, the March air becomes thick with the sweet song of frogs calling from the wet ditches, depressions and ponds of the Kankakee Sands Prairie Restoration.

You will remember that frogs and toads are amphibians, spending a part of their life cycle in water as opposed to reptiles that spend all of their time on land. Amphibians are often thought of as wet and slimy (whereas reptiles are thought of as dry and scaly) because of the thin layer of moisture on their body in that allows them to breathe through their skin!

In our Kankakee Sands region, there are 12 species of frogs and toads that might be calling during spring evenings. Frogs and toads are easily identified by their calls, like the high pitched ‘peeeeeep’ of the spring peeper or the plucked banjo string ‘plounk’ call of the green frog.

And let’s remember why frogs call, to attract a mate. How else would you find a lover in the dark of night? Frogs will call during their mating season in the spring, then quiet down for the summer and fall and finally hibernate in the winter.

One of the quietest members of the spring frog symphony, but one of the most abundant at Kankakee Sands is the Northern leopard frog (Rana pipiens). It is the frog you are most likely to see hoping ahead of you on the trail or bounding across the road, legs dangling behind it when it is airborne. After a rainstorm last year, there were zillions of Northern leopard frogs sitting in the road, and we had to drive home through them. Ugh! What a nightmare! Luckily the birds were there in the morning, cleaning up unfortunate frogs.

The historical range of the Northern leopard frog in Indiana was throughout northern, central, and southeast part of the state in freshwater sites with ample vegetation like wetlands, marshes, ponds and moist fields. In the summer they wander far from standing water through moist vegetation. Over the past 30 years, the numbers have declined so dramatically that now in Indiana the Northern leopard frog is federally listed as a ‘species of special concern’, which means it is being monitored but not yet managed as a protected species with Federal oversight. The Northern leopard frog may be declining in many parts of Indiana, but since the wet prairies of Kankakee Sands were created over the last decade, the Northern leopard frog is going strong here in Newton County.

The Northern Leopard Frog is 2-3.5 inches in length, a respectable size for a frog. Its base color can range from bright green to an olive green-brown; it will always have dark rounded spots on its back that resemble the spots of a leopard. Another key marker of the leopard frog is the dorsolateral ridges, two lightly colored, parallel ridges that extend down the body from the neck to the hips.

Like all frogs, the female Northern leopard frog lays eggs, and as she lays them the male fertilizes them. The Northern leopard frog lay up to 6,000 eggs in globular mass, which are attached by the female to plant stems. The tadpoles hatch from the egg masses in 13-20 days, and are dark grayish brown with golden flecks. Once the tadpoles hatch they are on their own, the female does not care for the young. (If you ever thought it was overwhelming to care for one baby, imagine trying to care for 6,000!) Over the next 70-100 days, the tadpoles will transform into adults taking on a green color with dark spots, slowly growing legs and absorbing their own tail. The rate of tadpole’s development is dependent on the temperature of the water. The warmer the water, the faster the development. The adult Northern leopard frog is capable of reproducing 2-4 years after hatching.

A Northern leopard frog’s diet consists of insects and spiders, slugs and earthworms, and occasionally other smaller frogs. A Northern leopard frog is part of the diet of birds, snakes, bull frogs, and small mammals like the raccoon and opossum.

The mating call of the Northern leopard frog is a low quiet deep rattling snore lasting 3 seconds followed by a ‘chuckling’ or the same sound that you can make by rubbing your thumb against a balloon. It is one of the quietest calls of all the frogs in our area. The call is often overpowered by the more robust calls of other species. However, the northern leopard frog is less secretive than other breeds and relatively easy to spot. Breeding season for the Northern leopard frog is mid-March to the end of April.

March on out to Kankakee Sands this March. During the day, go ahead and re-discover the joy of catching a frog, holding it in your hands, and then watching it hop away. During the night, enjoy the surround sound of the frog choirs at Kankakee Sands. Bets are on that you are sure to see a Northern leopard frog when you come.

If you are interested in taking part in frog call surveys or frog monitoring, there are several websites where you can learn more about becoming a frog monitoring volunteer.  FrogWatch USA or Indiana DNR Amphibian Monitoring Program . -Alyssa Nyberg, Kankakee Sands Nursery Manager



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