Sunriver Nature Center and 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)
The Oregon Spotted Frog is a candidate for listing as an endangered species. Sunriver is home to one of the greatest concentrations of Spotted Frogs in the frogs' range. This creates a unique opportunity to study the behavior 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.
Additional research at the Sunriver Nature Center and Observatory has led to a better understanding the two most dramatic types of amphibian deformities--extra limbs and missing limbs. The studies produced the first report of extra-limb deformities in Spotted Frogs. It was found that this species generally avoids exposure to trematode parasites that cause extra limbs by reproducing very early in the year, before the parasites emerge in July and August. Research on site, published in the journal Ecology, showed conclusive evidence of small predators, such as stickleback fish and dragonfly larvae, removing the 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, a member of the Nature Center's 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, no evidence has been found of serious problems for the frogs that would be caused by these parasites.
New Leech Species
While searching for the likely vectors of the blood parasites of Spotted Frogs, a leech commonly found on the frogs in the area was determined to be a previously undescribed species. Collaborations with Dr. Mark Siddall of the American Museum of Natural History, gave this leech the name Placobdella burresonae, and described 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. Sunriver Nature Center researchers collaborated with researchers from 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, it was 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. The call is shown here as a sonogram, showing a series of pulse with most of the sound energy between 500 and 1000 Hz.