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How to build a simple pond for native frogs
June 10, 2011
CORVALLIS, Ore. — If you build a frog pond, frogs will come. But only if roads don't stand in the way.
Students in the Oregon State University Extension Service 4-H Wildlife Stewards Program encourage home gardeners and their kids to create their own backyard frog pond in areas where the frogs can get to the newly created habitat and disperse to safe habitat after breeding.
The tiny Pacific chorus frog, formerly known as the Pacific tree frog, is the most abundant species of frog in Oregon and can live in many habitats: wooded areas, meadows, pasture, towns and even urban areas. They spend their time close to the ground, in grass and shrubs. When they lay their eggs, they must be near water. After breeding, they go back to terrestrial habitats. Make sure your pond is not surrounded by inhospitable habitat such as roads that would impede this local migration.
"Pacific chorus frogs are better than all the others at getting to available habitat, but they are still strongly limited by urban development and road systems," said Dana Sanchez, OSU Extension wildlife specialist.
Pacific chorus frogs range from bright green to brown, reddish or gray. They have a dark strip stretching from their nostrils to their shoulders that looks like a mask; some have dark stripes and spots on their backs. All can change color to match their background.
A pond for Pacific chorus frogs should be at least 20 inches deep and contain about half open water and half plants. Plants supply oxygen, hiding places and places to attach eggs. They also are attractive homes for the spiders and insects that frogs eat. Algae are important as food for the tadpoles, but too much sun makes too much algae. You’ll want to shade the pond to control the algae.
Take care to use only plants that are native to Oregon, found naturally in your area. The OSU 4-H Wildlife Stewards recommend a mix of plants: submerged (underwater), and floating and emergent (growing on the banks). A list of recommended native plants for frog ponds in Oregon can be found online.
In the spring, male Pacific chorus frogs find pools and ponds and call females to mate. When you hear frogs croaking in the spring, they probably are Pacific chorus frogs. The males hide in grass and shrubs and fill up their throat with air to make their call.
A female lays 400 to 750 eggs each year in groups of 10 to 70, held together by a slimy jelly. The groups usually look like small, loose clusters and are attached to grass, stems and sticks in the water. The eggs look lumpy and transparent with dark specks.
In about 10 to 12 days, the eggs hatch into brown tadpoles, which when fully grown are about two inches long, including their tails. Like fish, they breathe through gills and eat mostly algae and dead plants and animals.
Tadpoles go through metamorphosis, growing legs, losing their tails and gills and developing lungs. They go from being herbivores (plant eaters) to carnivores, eating bugs and other living creatures. Pacific chorus frog tadpoles usually are about two months old and one half inch long when they become frogs.
Let your pond dry out after the frogs emerge as adults. Ponds that dry out in late summer are good for Pacific chorus frogs because predators such as fish and bullfrogs cannot survive in a temporary pond. Insects, fish, snakes, birds, mammals, and other frogs eat Pacific chorus frog tadpoles. Adult frogs serve as prey for hawks, owls, skunks, raccoons and other critters. In the winter, the frogs hibernate and hide in leaves, logs and mud to stay warm.
OSU 4-H Wildlife Steward volunteers help students and teachers create and sustain wildlife habitat on school grounds. The National Science Foundation funds the program, which serves 62 schools in nine Oregon counties. More information is available on the 4-H Wildlife Stewards website.