Research

Sunriver Nature Center & Observatory maintains a research department that encourages original research in the natural sciences. Our research serves to inform staff and visitors to the Nature Center and contributes new insights to the scientific knowledge base through academic publications and participation in scholarly meetings.

The Oregon Spotted Frog

(Rana pretiosa) is a candidate for endangered species listing. Sunriver is home to one of the greatest concentrations of spotted frogs in it’s entire range, offering a unique opportunity to study the natural history of this amphibian throughout the year. Over the past 10 years, studies at the Nature Center have contributed a number of discoveries important to understanding the basic biology of this species.

Amphibian Deformities

Our research has contributed to understanding the two most dramatic types of amphibian deformities--Extra limbs and missing limbs. We provided the first report of extra-limb deformities in Spotted Frogs. We further showed that this species generally avoids exposure to trematode parasite that causes extra limbs by reproducing very early in the year and thereby avoiding the parasites that tend to emerge in July and August. In a recently-published article in the journal Ecology, we reported conclusive evidence that small predators, including stickleback fish and dragonfly larvae can remove hind limbs of tadpoles, leading to large numbers of newly transformed frogs or toads that are missing all or part of a hind limb.

Parasites of Oregon Spotted Frogs

Patty Stenberg, one of our research team, has found and described three kinds of blood parasites in Spotted Frogs, including an unknown species of Hepatozoon shown here inside a red blood cell. So far we have seen no evidence that any of these parasites cause serious problems for the frogs.

New Leech Species

While searching for the likely vectors for the blood parasites of Spotted Frogs, we learned that a leech commonly found on the frogs was a previously undescribed species. We subsequently collaborated with Dr. Mark Siddall of the American Museum of Natural History, to give this leech the name Placobdella burresonae, and describe the species in the Journal of Parasitology.

Chytrid Fungus in Amphibians

Over the past 10 years, a newly-identified fungus has been implicated in mass die-offs of amphibians across the globe. We have collaborated with researchers at other institutions to identify the wide-spread presence of the Chytrid Fungus in a number of amphibian species around Oregon, including native Western Toads, Spotted Frogs, Red-legged frogs, and non-native Bullfrogs (which may be carriers of this pathogen). 

Underwater Calls of Spotted Frogs

Through the use of a hydrophone, we discovered that Oregon Spotted Frogs engage in a previously unknown behavior that involves calling while totally submerged. These calls are identical to previously described advertisement calls heard at the surface when the frogs gather to mate and lay eggs. However, the submerged calls may be given several days before the frogs gather at breeding sites and at distances up to half a mile from the breeding site. Click here to listen to the Oregon Spotted Frog advertisement call: The same call is shown here as a sonogram, showing a series of pulses with most of the sound energy between 500 and 1000 Hz.








Click here for a bibliography of scientific publications

NC-bibliography-1.doc.