You might not be able to see them or catch them, but University of Victoria professor Caren Helbing can tell if the invasive American bullfrog is lurking in a local lake or stream.
The voracious amphibian has colonized water bodies around British Columbia in recent years, devouring native species and keeping residents awake at night with their loud croaking.
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Helbing, a professor in UVic's department of biochemistry and microbiology, has developed an improved method of testing water samples for DNA evidence of invasive or endangered species.
"We take water samples from lakes and rivers and we isolate the minute quantities of DNA in those samples," Helbing said in an interview with On The Island host Gregor Craigie.
The DNA evidence tells researchers if the species has been present in the water in recent days or weeks, without the need to locate a physical specimen for proof.
"A lot of times, especially with amphibians, finding them is really tough, so this is a way to get more reliable data," Helbing said.
Helbing said she has found evidence of the invasive American bullfrog in places where it wasn't expected to be.
"We looked at the local lake called Florence Lake [on southern Vancouver Island] where there were some extensive eradication efforts done a few years back."
"We found that there's still bullfrog DNA in that lake so they haven't been totally eradicated there."
Helbing, in collaboration with environmental consultants Hemmera Envirochem Inc., is also tracking endangered species, such as the Rocky Mountain tailed frog, found in southern British Columbia. She found DNA evidence of this species in places it had not previously been seen.
While scientists can now confirm the presence of a species from water samples, Helbing said, it is not yet possible to achieve "that holy grail of knowing how many animals there really are."
That will require further research on analyzing test results in different water conditions.
"We need to know how muddy the water is, and how fast the water flows and whether there was a storm there recently and stuff like that," Helbing said. "All of those things have bearing on the amount."
With files from CBC Radio One's On The Island
To hear the full interview, click on the audio labelled: DNA test tracks invasive species in lakes, rivers.