Rana pretiosa

The Oregon spotted frog is one of the newest species WPC is helping to save.  Now on the brink of extirpation from Canada, this frog is found only in British Columbia’s lower Fraser Valley, where it is believed that only 300 breeding individuals remain in small, widely scattered remnant populations.  In partnership with the Greater Vancouver Zoo, we launched a pilot husbandry program for this endangered species in 2011.  Initially, the program will be small and will incorporate studies to confirm the long-term survivability of released metamorphic frogs (individuals that have recently changed from tadpole to frog).  Frogs from the program are also needed to support other studies on habitat use and head-starting success.  Head-starting is a process where high-mortality life stages (such as larval and juvenile stages in amphibians), are protected and released after they have reached a certain size or life stage.  Transmitters will be used in some cases to track the frog’s movements (see photo top right). If successful, our long-term intention is to ramp up production in future years to enable more widespread reintroduction in support of wild population recovery.

Description

Adult Oregon spotted frogs have black spots with light centers and fuzzy edges, scattered on a brown or reddish-brown head and back region that becomes increasingly red with age.  Light brown to orange dorsolateral folds begin directly behind the eye and run over the tympanum along the back. Beyond the middle of the back, the folds become discontinuous and disappear as they approach the lower back. Juvenile Oregon spotted frogs are olive green or light brown.  The Oregon spotted frog deposits eggs in March. Egg masses are usually deposited in clusters (rarely singularly), and can be distinguished from the single egg masses of red-legged frogs.

Habitat

Adult Oregon spotted frogs are warm-water marsh specialists that prefer floodplain wetlands, side channels, and sloughs associated with permanent water bodies and emergent vegetation.  They prefer habitat with a large amount of open water and low to moderate amounts of cover by emergent vegetation.

Distribution and Population Size

The Oregon spotted frog is a Pacific Northwest endemic whose historical range extended from the Pit River drainage in northeastern California to the south, north to southwestern British Columbia and east to the Cascade Mountain range of Oregon and Washington.  In British Columbia, all historical and extant populations have been found in the Fraser River Lowlands.  The last remaining populations in Canada are found in four locations in the extreme southwestern corner of British Columbia, an area generally referred to as the Fraser River Lowlands.  The Oregon spotted frog was listed as endangered in 1999 by the Committee on the Status of Endangered Wildlife in Canada.

In comparison to numbers documented in Washington, populations in British Columbia are extremely small.  Egg mass counts in 1997, and between 2000 to 2010 at sites in British Columbia indicated that estimates of Canada’s entire breeding population varied from a low of 116 breeding adults in 2007, to a high of 548 breeding adults in 2002.  Counts in 2009 found only 153 egg masses in the B.C. population.

Threats to Survival

Habitat loss as a result of land developments, agricultural land conversion, resource extraction and hydrological alterations has occurred historically and is likely the predominant cause of the decline of the Oregon spotted frog throughout its North American range.  With only four remaining Canadian breeding populations (one of which may be near extirpation), and less than 350 estimated breeding individuals, the risk from demographic and environmental stochastic events is high and could result in further local extirpations.  Threats with a very high or high overall impact on the Oregon spotted frog include invasive and other problematic species and genes, human intrusions and disturbance, and pollution.

What you can do to help

• Make a contribution today towards WPC’s Oregon Spotted Frog recovery activities.

• Help reverse the loss of frog habitat by protecting or restoring wetlands and surrounding vegetation on your property.