Amphibians

Oregon Spotted Frog

Rana pretiosa · also called Oregon spotted frog

Vulnerable ↓ insectivorecarnivore Rivers & wetlands Temperate grassland

The Oregon spotted frog barely leaves the water. It is the most aquatic native frog in the Pacific Northwest, a marsh animal that hunts, basks, breeds, and overwinters within a metre of open shallow water. That habitat — warm, wet, low-lying valley marsh — is also the habitat people have drained the hardest, and the frog has followed it out of about 90 percent of its former range.

Overview

The Oregon spotted frog, Rana pretiosa, is a brown, dark-spotted, red-bellied frog of marshes, wet meadows, and slow spring channels from southwest British Columbia to northeastern California. Its species name means “precious”. It is an insectivore that hunts almost entirely in and just above the water, and it is extremely water-bound — rarely straying, and overwintering submerged in springs and mud.

A collapsed range

Once found through the Fraser Valley, the Puget lowlands, and the Willamette Valley, it has vanished from about 90 percent of that range, especially the valley bottoms, and now survives mainly in scattered sites in the Cascade foothills of Oregon and Washington, plus a few tiny populations in British Columbia — one of the most endangered amphibians in Canada.

Why it declined, and the response

Lowland marshes were drained for farming and towns; the survivors were choked by invasive reed canarygrass and invaded by bullfrogs and warm-water fish that eat the eggs and tadpoles; dams changed water levels. Recovery now centres on restoring shallow open water, controlling the grass, removing bullfrogs, and head-starting eggs at zoos for release.

Status

Vulnerable (IUCN) and Threatened under the US Endangered Species Act since 2014, with designated critical habitat. Several managed sites are now stable or growing, but the species remains at serious risk.

Oregon Spotted Frog: common questions

What is the difference between the Oregon spotted frog and the Columbia spotted frog?

They were considered one species until 1996 and still look very similar, both being brown frogs with dark spots and reddish or orange colour on the underside of the legs and belly. They are separated mostly by range and habitat. The Oregon spotted frog lives in the lowlands and foothills west of and within the Cascades, is extremely aquatic, and is rare and declining. The Columbia spotted frog occupies a much larger area east of the Cascades through the northern Rockies and into Alaska, uses a wider range of water bodies, spends more time away from water, and is far more common. Where their ranges approach each other in the Cascades, they are told apart by genetics and by fine details of the eyes and skin.

Why has the Oregon spotted frog become so rare?

Because it depends on exactly the kind of habitat that has been most heavily destroyed in the Pacific Northwest — warm, shallow, permanently wet, open marsh and wet meadow in valley bottoms. Most of those wetlands were drained, diked, and converted to farmland and towns over the last century and a half. What remained was then degraded by the spread of reed canarygrass, which fills the open shallow water the frog needs to breed and bask, and invaded by American bullfrogs and non-native warm-water fish that eat the eggs, tadpoles, and young frogs. Dams and water diversions changed the timing and depth of water in the surviving marshes. The frog cannot travel far over land to find new sites, so once a wetland is lost, its frogs are usually gone for good.

What is being done to save it?

A coordinated recovery effort is under way across its range. Key wetlands are being protected and restored, with active control of reed canarygrass by mowing, targeted grazing, and managed flooding to reopen shallow water, and removal or exclusion of bullfrogs and invasive fish where possible. Several zoos, including the Oregon Zoo, Woodland Park Zoo, and Vancouver Aquarium, run head-start programmes that raise wild-collected eggs to froglet stage and release them, which has boosted some populations. Water management behind dams is being adjusted to provide stable breeding conditions. The species remains at serious risk, but a number of the managed sites now have stable or growing populations.

Is the Oregon spotted frog dangerous or toxic?

No. It is a small, harmless frog, generally 4 to 10 centimetres long, with no significant skin toxins beyond the mild, slightly distasteful secretions common to many frogs, and it neither bites nor poses any risk to people or pets. If anything it is exceptionally vulnerable itself, being slow, tied to shallow open water, and heavily preyed upon. The main way people interact with it is through conservation work and, for a lucky few, seeing one at a protected marsh in central Oregon during the spring breeding chorus, when males give a soft, low, knocking call from the shallows.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 10, 2026. Last updated September 10, 2026.

Quick facts

Scientific name: Rana pretiosa
Diet: Insects, spiders, and other invertebrates snapped from the water surface and emergent plants, along with small frogs, tadpoles, and the occasional small fish, taken by a highly aquatic frog that hunts almost entirely in and just above shallow water
The most water-bound frog in its range: The Oregon spotted frog spends more of its life in water than any other native frog of the Pacific Northwest, rarely moving more than a metre or two from the water even to bask, and overwintering underwater in springs and in the soft mud of ponds and channels
Its name means precious: The species name pretiosa is Latin for precious or valuable, given in 1853, and the frog has become precious in a different sense as one of the rarest amphibians in the western United States, a symbol of the vanishing wetlands of the region
Warm shallow breeding water: Females lay their eggs communally in the same few sunlit spots year after year, in water often less than 10 cm deep, so the black egg masses, sometimes dozens laid side by side, warm quickly in the sun, but this also leaves them exposed to a late frost or a drop in water level
Down to scattered remnants: The Oregon spotted frog historically ranged from southwest British Columbia through the Puget Trough and the Willamette Valley to northeastern California, and it has vanished from around 90 percent of that range, including almost all of the lowland valleys, surviving mainly in a scatter of sites in the Cascade foothills of Oregon and Washington and a few tiny populations in British Columbia
Threatened by an invasive grass: Reed canarygrass, a fast-growing introduced wetland grass, forms dense stands that choke the open shallow water the frog needs for breeding and basking, and controlling it by mowing, grazing, or flooding is now a central part of Oregon spotted frog recovery
Bred at zoos for release: Several zoos and agencies run head-start programmes, collecting wild egg masses, raising the tadpoles and froglets in safety past the stage when most would be eaten, and releasing them back into restored and protected wetlands to rebuild populations
Range: The Pacific Northwest of North America, historically from the Fraser Valley of southwest British Columbia south through the Puget lowlands and the Willamette Valley of Oregon to the Pit River drainage of northeastern California, now reduced to isolated sites, chiefly in the Cascade Range foothills of central Oregon and southern Washington, in marshes, wet meadows, slow spring-fed channels, and the shallow vegetated margins of ponds and lakes.
Conservation status: Vulnerable ↓ ≈ The Oregon spotted frog is listed as Vulnerable by the IUCN and as Threatened under the US Endangered Species Act since 2014, with critical habitat designated, and it is endangered in Washington and a species of concern in Oregon, while the Canadian population is one of the most endangered amphibians in Canada with only a few hundred breeding females. The causes of its decline are the draining and filling of lowland marshes for agriculture and development, invasion of its breeding shallows by reed canarygrass, predation of eggs and tadpoles by introduced American bullfrogs and warm-water fish, altered water levels behind dams and diversions, and drought in the wild