So many people have dumped their pet turtles that it's threatening B.C. species, says biologist

When biologist Aimee Mitchell began her tally of endangered coastal western painted turtles 15 years ago, she says it was impossible to ignore the number of discarded pet turtles thriving in the wild.

The invasive red-eared sliders, which grow larger than the coastal western painted turtles — B.C.'s only native turtle — were crowding sunbathing spots.

Her team's most recent study was the first to confirm that the freed red-eared sliders are successfully reproducing in the same territory as the West Coast population of western painted turtles.

This population of turtles — that spans south along the Sunshine Coast, Gulf Islands and Vancouver Island — hit a low of about 3,000 before hatchlings were released over the past few years, Mitchell says.

Mitchell and her colleagues tallied turtles at 19 spots, confirming the invasive turtles were overtaking endangered western painted turtles — which were outnumbered 2.5 to one.

"It is surprising," said Mitchell, the program manager for the Coastal Painted Turtle Project.

WATCH | How invasive turtles are pushing out native species:

Before the work her team did, it was believed that red-eared slider turtles could survive in the wild, but would fail to successfully reproduce given the shorter egg incubation period in Canada.

"It surprised the province as well," said Mitchell, who has focused on species at risk throughout her career.

"Until we proved that they were fully successfully hatching, the province didn't consider them invasive."

By 2016, B.C. ruled red-eared sliders are an invasive species.

The proliferation began when these turtles were sold as pets. People took home a coin-sized paddler, and it grew to the side of a dinner plate. A captive turtle can also live to 50 years old. Many owners released them into the wild.

Mitchell says she would like to see efforts to remove and cull invasive turtles on a large scale, to save the threatened native species. So she's doing further study, urging people to report sightings of turtles so they can map their evolving territory, and says she hopes more work is done to study the effects of the invader on precarious populations like the coastal population of painted turtles.

Painted turtles are found in Southern Canada from B.C. to Nova Scotia. They live in shallow, slow-moving water. They like mud.