The Oregon spotted frog, rana pretiosa, is one of the “true” frogs of the world (like the Florida bog frog). Males are slightly smaller than females, reaching 1.8 to 2.9 inches (4.5 to 7.3 centimeters) in length while females measure 2.4 to 4 inches (6.1 to 10 centimeters) long. They weigh in at anywhere from 0.8 to 3.1 ounces (25 to 90 grams). Their color can vary from olive green, to brown and even brick red. They have many large, irregular black spots (often with lighter-colored centers) along the top of their bodies. Their undersides on the other hand, are mottled with a red or orange color which looks as though it has been painted on the skin as opposed to being its natural look.
The Oregon spotted frog can be found in both Canada and the United States of America. They are a highly aquatic species, and are almost always seen in or near a permanent still water source such as a pond, lake, marsh, and or spring as well as the grassy margins of slow-moving streams. They can sometimes be found at elevations of up to 5,150 feet (1,570 meters). When winter comes around an Oregon spotted frog will move to channels and springs that will not freeze over completely and remain there through the coldest months.
The diet of an Oregon spotted frog consists primarily of insects, spiders and earthworms. They may even eat smaller frogs should the opportunity present itself. Ambushing is the preferred hunting style of this animal. Since they are not very fast, they will avoid potential danger (such as a bullfrog) by swimming away short distances (or to the bottom of the water) and finding a place to conceal themselves.
Breeding season for the Oregon spotted frog takes place in February or March for those at lower elevations, and in late May to early June for the higher elevation populations. Males will congregate in shallow water and call out to attract females. After females have laid their clutch of 598 to 643 eggs, they will leave and continue with their solitary lives. Males on the other hand, will continue to call out and mate with females for up to a month. The first tadpoles will usually hatch (which takes around 18 to 30 days depending on temperature) before the last few males leave the breeding grounds. The tadpoles will graze on algae and rotting vegetation, which provides nutrition due to the bacteria which lives on the decomposing plant material. Tadpoles will metamorphose into juvenile frogs at 13 to 16 weeks of age. If the young ones can survive long enough, then they can live to be up to 8 years old.
The Oregon spotted frog is, overall, a threatened species. It was only recently considered a species of its own and as a result, population numbers are not concrete. It is known however, that these amphibians have lost most of their historic range and must be studied to better understand how to protect them. Hopefully, research proves fruitful so that the Oregon spotted frog can regain some of their lost home range and live peacefully with humans. After all, such a unique amphibian deserves to live and prosper for many years.
Works Cited
“Oregon Spotted Frog” 1 August 2011
“Rana Pretiosa – Oregon Spotted Frog” 1 August 2011
“Oregon Spotted Frog” 1 August 2011