East Kootenay Northern Leopard Frog Project

by Cameron Gillies and Renee Franken of Tierra Consulting

Northern Leopard Frogs (Rana pipiens) were once a relatively common component of the Columbia Basin’s living heritage.  They ranged across southern British Columbia including parts of the Rocky Mountain Trench.  Now, Northern Leopard Frogs are known from only a single population in all of British Columbia, located at Creston.  They are recognized as a prime example of the declines that have affected amphibian populations around the world.

The primary objectives of this project were to: 

Amphibians around the world have undergone recent and widespread declines.  The causes of these declines have been widely varied and in many cases are completely unknown.  Declines often appear to be caused by a combination of factors and including; habitat loss, habitat fragmentation, pollution, climate change, introduction of foreign species of amphibians and fish, increased ultraviolet radiation due to thinning of the ozone layer, and disease.  Areas affected have ranged from seemingly pristine locations such as Yosemite National Park (Drost and Fellers 1996) and the cloud forests of Central America (Pounds and Crump 1994; Berger et al. 1998) to more obviously impacted landscapes such as the Grand Central Valley of California (Fisher and Shaffer 1996).  Additionally, not all species are affected equally.  Some species have gone extinct beside others that seem completely unaffected.  These declines are a topic of global concern particularly because amphibians are seen as indicators of environmental quality.  Amphibian skin is very permeable, allowing pollutants in the environment to be readily absorbed.  They are dependent on moist or wet habitats making them susceptible to global climate changes that may dry out some of these habitats.  They are also vulnerable to both water and air pollution due to their two life stages; larvae or tadpoles (water) and adults (air).  Much effort around the world is focussed on describing these declines, addressing questions about them and attempting to determine what can be done to slow or stop them.

Once relatively common across southern Canada and the northern United States, Northern Leopard Frogs have since declined over much of their western range.  They have disappeared from many sites in the Canadian prairies (Manitoba, Saskatchewan and Alberta) and are very rare further west in British Columbia, Idaho, Washington and Oregon (Weller and Green 1997).  As close as anyone can estimate, the decline of Northern Leopard Frogs occurred in the late 1970’s and early 1980’s although reports of the decline from British Columbia are very sparse during that period so the timing of the decline is very unclear (Orchard 1992).  The cause of the decline is also unknown.  It appears that nobody investigated the cause of the decline while it was happening so researchers are now limited to speculation on the cause or causes.  Unfortunately, it is probably not possible to learn any more about why this once common amphibian has become so rare because this requires examination of the causes while the decline is occurring.

As a result of this decline in numbers across their range, the B.C. population of Northern Leopard Frogs is considered endangered, federally, by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).  The prairie population of Northern Leopard Frogs is considered vulnerable and the eastern populations in Ontario and Quebec are considered not at risk (COSEWIC 1999).  The COSEWIC categories of; vulnerable, threatened, and endangered cover species which are under increasing threat or danger.