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Rare frogs seen at Sellwood Riverfront Park

by: Rita A. Leonard A tadpole at rest, at right, in the posted pond at Sellwood Riverfront Park. Looks like an egg mass in the water at left.

In an era in which frog populations have been declining around the world, for as-yet-unclear reasons, there is a positive story about frogs emerging in the shadow of the Sellwood Bridge.

Our long cold rainy spring finally warmed up enough by May to encourage frogs to lay their eggs, and now signs posted by Portland Parks and Recreation at the small pond in Sellwood Riverfront Park indicate that an endangered frog known as Rana Aurora, or northern red-legged frog, has been spotted in the area. Visitors are asked to keep dogs out of the pond in order to maintain a safer habitat for these small amphibians.

Oaks Bottom and other local wetland areas offer opportunties to study amphibian life cycles, as well as those of other critters that inhabit damp environments, such as snakes, water bugs, and dragonfly larvae. These creatures form the base of the wetland food cycle, and are eaten by many birds and wetland predators. Frogs especially are indicators of the health of ecosystems, since their eggs and young are exposed to the elements.

If you go looking for these rare frogs, here's how to recognize them. Red-legged frogs range from 2 to 5 inches in body length, with relatively long, dark-banded legs. They are gray or brownish, with black dots and splotchy spots on their backs. Their bellies are yellow, with pinkish red on the lower abdomen and hindquarters.

They prefer cooler, slow-moving waters as habitat, especially those with cattails and bulrushes. R. aurora attach their egg masses to these plants underwater, unlike other frogs whose egg masses float free in the water.

If you go to observe the wildlife, remember to minimize damage, pick up trash, and 'leave only your footprints' in our urban natural areas.